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Publication Number: FHWA-HRT-13-048
Date: October 2013

 

Driver Expectations When Navigating Complex Interchanges

Chapter 3. Task 4-Gather Feedback from Drivers

The overall objective of task 4 was to collect qualitative information about driver expectations from drivers in accordance with the methods outlined in the task 3 protocol. Twelve focus groups in three metropolitan areas (Seattle, WA; Columbus, OH; and Washington, DC) were used to obtain driver opinions, thoughts, and beliefs about their expectations in complex interchange scenarios. In particular, the specific objectives of the focus groups were to obtain information about the sources of expectation-related problems that drivers encounter and the kinds of remedies that drivers suggest for these problems. This includes aspects such as what makes drivers comfortable or uncomfortable in certain interchange scenarios. These objectives were addressed by having participants view video footage of a vehicle navigating a complex interchange and asking them questions and engaging them in discussions at various points during the video. An effort was also made to obtain information that could be used in future project tasks. This included asking drivers about their general strategies when navigating interchanges, specific actions they take, what type of information they look for when making certain decisions, and when and where they seek this information.

This chapter contains the following three technical sections:

Task 4 Methods

This section describes the methods used to conduct and analyze the focus group data.

Participants

This section describes the general approach for selecting focus group locations and defining the participant demographic make-up of each session as well as the recruiting methods.

Focus Group Locations

The general approach for determining the focus group locations was to select locations that had large urban populations serviced by major freeway interchanges. Resources were set up to support participant recruitment and conduct the focus groups. This approach helped lower costs and reduce risks associated with having to conduct these activities remotely. Based on these requirements, the selected focus group locations were Seattle, WA; Washington, DC; and Columbus, OH. Four focus group sessions were held in each location.

Demographic Sampling Objectives

Each focus group session was comprised of up to 12 licensed adult drivers2. Individual focus group sessions were open to drivers of all age groups; however, researchers tried to balance age and gender in each. In particular, an approximately equal number of males and females was scheduled from each of the young (< 30), middle (30-55), and older (55+) driver age groups. Table 4 shows the actual demographic composition of the sessions.

Table 4. Demographic composition of each focus group.

Session

Women's Ages

Men's Ages

Total

18-35

36-54

55+

18-35

36-54

55+

Seattle, WA, April 19, 6 p.m.

2

2

2

2

1

2

11

Seattle, WA, April 21, 2 p.m.

2

1

1

1

0

2

7

Seattle, WA, April 21, 6 p.m.

0

2

2

2

2

2

10

Seattle, WA, April 22, 6 p.m.

1

2

2

1

2

2

10

Columbus, OH, April 27, 2 p.m.

1

2

2

1

2

2

10

Columbus, OH, April 27, 6 p.m.

2

2

2

2

2

2

12

Columbus, OH, April 28, 2 p.m.

1

2

2

1

2

2

10

Columbus, OH, April 28, 6 p.m.

1

2

2

1

2

1

9

Washington, DC, May 4, 2 p.m.

1

3

0

2

2

2

10

Washington, DC, May 4, 6 p.m.

2

1

2

1

1

1

8

Washington, DC, May 5, 2 p.m.

0

0

2

1

2

0

5

Washington, DC, May 5, 6 p.m.

1

2

2

2

1

1

9

Total

14

20

22

16

19

19

111

Print and online advertisements were the primary methods for recruiting drivers. Specifically, recruitment advertisements were posted in the following sources as needed: Craigslist®, local newspapers, and the contractor's driving study recruitment Web site.

One concern with the focus groups was that the number of participants in each session was expected to be relatively small (nine or less as originally planned). Small sessions run the risk of having a reduced diversity of viewpoints. This issue was addressed in two ways. The first was to include a mix of driver ages and genders in each session to promote differences in driving experience and strategies. The second was that group discussions were supplemented with individual written responses to key interchange driving questions. This provided additional data and reduced data transcription requirements.

Procedures and Materials

The primary data collection activity was the discussion of interchange scenarios using a dynamic scenario presentation (video-based), including individual discussion questions in a scenario response booklet. The following sections describe the primary data collection methods and corresponding materials that were used to present the focus group stimuli.

Dynamic Scenarios

The dynamic scenario approach involved a video-based depiction of a single drive/maneuver through an interchange which started well in advance of the interchange and ended some time after the maneuver was compete. This approach is described in more detail in the following sections.

General Approach

Dynamic scenarios involved participants viewing a video recording of a drive through an interchange. The moderator introduced the activity by explaining to the participants that they would be viewing a video of interchange driving. Each scenario began with participants being given an overview of the driving objectives for the scenario and any other relevant context.

The same video scenario was shown to participants three times. The first time was used to collect individual responses from participants without a group discussion. Specifically, participants were shown the scenario video, which was paused at key points in the drive (referred to as "critical points" (see figure 3)). These critical points corresponded to times or locations in which drivers needed to make key decisions, where they may have had difficulty, or where their expectations were of particular interest (e.g., after viewing a guide sign). During these pauses, participants were asked questions, and they wrote down answers individually. The response booklet used in this activity is provided in appendix A. This process was repeated until all critical points within a scenario had been covered.

This illustration highlights the focus group video discussion method. There are three screen shots of a progressing driving scenario with pause symbols for each one. There is also an arrow pointing from left to right to indicate the video sequence. The video was paused at critical points for discussion purposes.
Figure 3. Illustration. Focus group video discussion method.

The second time, the video was shown without interruptions so that participants could get a sense of the flow and timing of the entire drive.

The third time followed the same procedure as the first viewing; however, the pauses were used to engage participants in discussions of the questions about their expectations and their understanding of the situation at that point in the drive. When suitable, the moderator probed participants about driving difficulties, violations of their expectations, and potential remedies for these problems.

Materials

The primary experimental materials were videos of a pilot vehicle navigating the selected interchanges. The videos were filmed from the perspective of a person traveling inside the vehicle. The entire video was geared toward a single interchange scenario with one driving objective (i.e., exiting at a left exit, choosing an exit lane at a two-lane exit, navigating closely spaced critical points, etc.). Each video contained two to four critical points depending on the nature of the interchange and the driving maneuver.

Note that because of the quality of the video footage, sight distances for signs were shorter than in the real world. Participants were provided with separate pictures of the key information sources during the critical points (i.e., higher resolution printed images of overhead signs) to ensure that they had all the information they needed to make relevant driving decisions.

An important concern with the production of video footage was the possibility that drivers may be familiar with the interchanges and know immediately how to execute the maneuver without additional information about the interchange. Not only would this undermine the researchers' ability to investigate how interchange signage and other elements affect driver expectations, but it would also introduce an unwanted source of variance across participants and locations. This was particularly a concern for the focus groups in Seattle, WA, which is where the researchers were based and where it was most cost effective to film the scenarios.

To address this problem, interchanges in Portland, OR, were filmed. These interchanges were far enough away that most Seattle, WA, drivers were unfamiliar with them. Researchers also tried to screen out Seattle, WA, participants who had spent significant time driving in Portland, OR, or who had lived there in the past.

Selection of Interchanges

Three interchanges were selected from those available in the greater Portland, OR, area. The criteria for selecting them was somewhat opportunistic based on which complex interchanges were available in the area and filming constraints (e.g., lighting). Candidate scenarios were evaluated based the types of complexity elements that occurred during each scenario drive. The complexity elements were comprised of those from Chrysler et al. and from those found in the task 2 literature review of this project (see table 5).(33) An overview of each of the three selected scenarios is provided in the following section.

Interchange 1: Visually Challenging Option Lanes

Drivers start on the bridge portion of I-405S/US-30W with the intention of following US-30W. Drivers begin in the left middle lane and must change into the right middle lane to exit using the option lane. After exiting, they encounter another option lane that services the Vaughn Street exit and US-30W. Drivers stay to the left of the gore point to continue on US-30W (not shown in the video). This scenario highlights option lanes, sightlines limited by roadway geometry, and misaligned arrow-per-lane symbols.

Interchange 2: Four-Lane Split with Complex Advance Guide Signs

Drivers start by driving straight on US-30W with the intention of following the signs to City Center. They are in the middle lane when they encounter the first sign for the upcoming roadway split. The first advance guide sign shows City Center as a destination, and the rest do not. When they reach the split, their lane becomes an option lane, and they follow the left leg to City Center. This scenario highlights inconsistent advance signage, limited visibility of signage due to obstructions, and multiple destinations in a close area.

Interchange 3: Poorly Signed Left Exit with Multiple Lane Changes

Drivers start by merging with US-30E onto the I-405N/US-30E bridge with the intention of taking the I-5S exit at the end of the bridge (they have not yet encountered guide sign information about this maneuver). They begin in the right middle lane. Because drivers do not know where the exit is, a potential course would be to choose a suitable lane based on prior expectations. The guide signs appear shortly before the exit, and drivers must make two rapid left lane changes into the option lane to exit onto I-5S/US-30E. This scenario highlights inadequate advance guide signs, an exit in the opposite direction of driver expectations, and lane changes under time pressure.

Table 5 shows the identified complexity factors for each scenario.

Table 5. Complexity factors identified for each scenario.

Complexity Factor

Interchange 1

Interchange 2

Interchange 3

Limited visibility of signage/ diverge points due to obstructions

 

X

X

Sight lines limited by roadway geometry

X

 

 

Visually cluttered/complex signage

X

X

X

Inadequate sign guidance

 

 

X

Low degree of guide sign consistency

 

X

 

Misaligned lane arrows

X

 

 

Pavement marking information

X

X

 

Exit decision required before driver is in immediate interchange vicinity

X

X

X

Limited decision time for required lane-change maneuvers

 

X

X

Closely spaced merge/diverge

 

 

X

Exits that diverge in direction opposite of expectations

 

 

X

Option lane

X

X

X

Lane drop

 

 

 

Route split

 

X

 

Multiple exit lanes

X

 

 

Multiple destinations in a close area

X

X

X

Through movement looks like or feels like an exit

X

X

 

Route running in a different cardinal direction than is designated

 

 

 

More than two major highways/ freeways at interchange area

X

 

X

System/service interchange combination

X

 

 

Multiple exits/destinations served by single freeway exits

X

X

 

X indicates "contains factor."

Focus Group Topics

A primary objective of the focus groups was to obtain information from drivers about their expectations at interchanges and about the problems they encounter when navigating complex interchanges. This included identifying the sources of expectation-related problems and the types of remedies that drivers may employ to deal with these problems. However, the specific set of topics addressed depended on the available driving scenarios. Based on this set, it was possible to cover the following topics (additional information about these topics is provided in the Moderator's guide in appendix B):

Focus Group Questions

The primary data collected in the focus groups were comprised of the individual participant responses to questions and group discussion summaries that occurred at the critical points in each scenario. These critical points were selected to correspond with times or locations in which drivers needed to make key decisions, where they may have had difficulty, or where their expectations were of particular interest. The questions included both specific references to ongoing elements at those points and general questions about the problems that drivers could be experiencing with the interchange. The final list of questions is included in the moderator's guide (see appendix B).

The focus group sessions also included a warm-up activity in which the groups discussed common characteristics of simple interchanges based on participant responses. This activity accomplished an important objective in that it gave participants the correct frame-of-reference to provide the desired level of detail for their comments during the focus groups. It also got participants thinking about their baseline expectations at interchanges without explicitly telling them what the researchers were looking for. Specific instructions to prime participants are potentially counterproductive when collecting expectation information because they unduly influence the issues that drivers focus on when providing their responses.

Session Timelines

The overall session length was expected to be 90 min with a break about halfway through. The following list provides a general overview of the timeline for the sessions:

Data Analysis Plan and Objectives

The raw data in the analysis were the words, phrases, sentences, and non-verbal responses of the focus group participants. The analysis followed a similar approach to one that has been used in other focus group research for the Federal Highway Administration.(35) Focus group sessions were attended by the moderator and another researcher who primarily acted as an observer/note taker and helped with focus group materials. Both these personnel were responsible for the analysis, and they examined all data (video recordings, notes, and post-session summaries) for patterns emerging from participant discussions. To analyze and summarize the focus group discussions, both the moderator and observer performed the following tasks:

The basic demographic and driving history questionnaire data were entered into a Microsoft Excel® spreadsheet, and any discrepancies were resolved by visual inspection to ensure data entry accuracy. Descriptive statistics were calculated for these and any written or survey responses that required a quantitative or categorical answer.

Task 4 Results

The results for the warm-up activity and the primary focus group discussions are presented in the following sections.

Warm-Up Activity Results

Before beginning the dynamic scenarios, drivers were asked some general questions about their expectations at freeway interchanges during a warm-up activity. They were asked to think about what they would expect at a simple interchange traveling from a three-lane freeway onto a major local road. Figure 4 shows a photo shown to participants during the warm-up. The moderator then walked through a set of questions in each focus group session, and participants provided their responses.

This photo shows an interchange shown to focus groups during the warm-up activity. There is a three-lane highway with cars traveling forward.
Figure 4. Photo. Interchange shown during the warm-up activity.

For each focus group, researchers kept record of whether or not the group mentioned a particular response. If a response was given by at least one individual in a group, the group was included in the count for that response option. The responses given by the majority of the groups (at least seven different groups) are shown in table 6. This table represents driver baseline expectations for simple, easy-to-navigate interchanges, and it serves as a comparison for driver expectations for the more complex interchanges discussed in the main part of the focus group sessions. The complete set of responses is shown in appendix C.

Table 6. Summary of the most common responses given during the warm-up activity.

Question

Most Common Response

Number of Groups

Where is the exit?

On the right

12

How many lanes would the exit have?

One lane

11

What happens to the travel lane after the exit?

It exits and also continues (option lane)

11

Where are the signs placed?

Overhead

7

How far ahead of the exit are the signs?

1 mi

7

0.5 mi

8

Are there multiple sets of signs?

Yes

7

What should the signs say?

Destination name

8

Exit number

8

Exit distance

8

Do you rely on lane markings?

No consensus of respondents

Focus Group Discussion Results

The results of the focus group discussions are presented in the following sections, which are organized by scenario. Each scenario begins with a description of the roadway, including an aerial view of the interchange showing the driving route and key interchange features/challenges encountered along the way. The scenario driving objectives are also described. These are followed by an overview diagram of the scenario (see figure 5 for a description of the elements in the diagram) and an image of the driving scene at each critical point with an accompanying list of discussion points. The discussion topics for each critical point were based on the interchange complexity factors listed in table 5, in addition to other aspects of the critical point that might influence driver expectations (driver expectancy factors). This information was included in the scenario summaries because it represents some of the elements of interchange driving that were focal points of the discussions.

This illustration highlights information elements in scenario overview diagrams. Each diagram contains a schematic of the interchange drive, a depiction of the driver vehicle and maneuver, signage at the critical points, and other signage on the roadway.
Figure 5. Illustration. Description of information elements in scenario overview diagrams.

Following the scenario overview information, each critical point is discussed in sequential order. This discussion begins with a brief description of the critical point and an image of the scenario driving scene, which shows some of the key information that participants refer to in their discussions (this image is a larger version of the one shown in figure 5). Also included in this section are the results of the response booklet questions.

The primary results of the focus group discussion are presented after the critical point driving scene images. These are comprised of brief descriptions of key themes and opinions/ideas discussed at each critical point. Because each critical point represents a unique set of driving circumstances, the discussions covered different types of topics, although there were recurring elements across critical points. In order to facilitate reading of the discussion points, they were presented using a similar structure in each critical point discussion. The high-level discussion categories included the following:

Note that depending on the nature of the discussions, not all of these categories were covered for each critical point. Within each category, key themes and opinions/ideas were summarized. These were typically followed by one to three quotes that were representative of similar comments made by participants. One objective of the example quotes was to capture some of the nuances of the associated comments. These summaries also provided a general sense of the frequency with which a theme or opinion occurred or the level of agreement among participants. In particular, each summary statement included a reference to a magnitude level. The magnitude terms used were based on the following scale:

One < Few < Some < Several < Many < Most < Almost All

The quotes are provided without attribution to individual drivers (to protect privacy), and the demographic category of the speaker (age, gender, and location) were also omitted. During the analysis, it became clear that there were almost no consistent response patterns based on driver demographics. A likely explanation for this is that all demographic groups were represented in most focus group sessions. Consequently, to simplify the presentation of quotes, this information was excluded. Also, some quotes were edited for readability, and missing words were added (denoted by square brackets). Care was taken to preserve the intended meaning of the comments.

Scenario 1

Roadway Description

The roadway in scenario 1, which was located in Portland, OR, was primarily the upper deck of a bridge that exited to a freeway. The bridge deck had four lanes, all moving in the same direction. The sight distance on the bridge was limited by crest vertical curvature. Figure 6 shows an aerial view of the roadway.

This photo shows an aerial view of the scenario 1 roadway. There is a four-lane freeway bridge deck highlighted in yellow that spans across a body of water. It then splits to the left and the right, with the yellow highlighting following the path to the right. The solid yellow line indicates the extent of the video footage. The line then becomes dashed, which indicates the remainder of the intended route, not shown during the scenario.
Original image: ©2011 Google®; map annotations
provded by Battelle (see "Acknowledgements")
Figure 6. Photo. Aerial view of scenario 1 roadway.(36)

The extent of the video footage is shown as a solid yellow line, and the remainder of the intended route is shown as a dashed line.

Driving Objectives

Drivers were told that their objective was to get onto Route 30 West. Figure 7 shows the signs that drivers encountered and the maneuvers that they had to make during the scenario drive. The relative locations of critical points are also highlighted.

This illustration shows sign information and required vehicle maneuvers in scenario 1. There is a four-lane single direction highway that splits to the left and the right at the top, with two lanes in each direction. At the base of the highway, there is a sign that indicates it is critical point 1. This sign lists a destination with an arrow for each lane on the roadway. At the point in the highway where the split occurs, there is a second sign that indicates it is critical point 2. This sign shows multiple destinations as well as an additional arrow, denoting that one lane will split into two lanes. After the curve to the right, there is a third sign that indicates it is critical point 3. This sign bank depicts exit only lanes as the leftmost and rightmost lanes. The other lanes are listed with destinations and downward arrows.
Figure 7. Illustration. Sign information and required vehicle maneuvers in scenario 1.

Scenario 1 Critical Point 1

At the first critical point, drivers were faced with two overhead guide signs with arrow-per-lane directions (see figure 8). Because of the crest vertical curve, drivers did not have a view of the roadway geometry ahead.

This photo shows the driving image for scenario 1 critical point 1. There is a four-lane single direction bridge deck with vehicles traveling on it. The sign above the left-land lane is labeled  City Ctr  with a down arrow. The next lane has a sign labeled  Beaverton  with a down arrow. The third lane has a sign labeled NW Ind. Area  with a down arrow, and the right-hand lane has a sign labeled  St. Helens  with a down arrow. Above the two right-most lanes, there is also a sign labeled  Exit 3.
Figure 8. Photo. Image presented to drivers for discussion in scenario 1 critical point 1.

Key topics for this critical point in the group discussion included the following:

Response Booklet Question

Since drivers' sight distance was limited by the crest vertical curve in the bridge, they were asked to respond with which of the roadway geometries in figure 9  through figure 13 they expected based on the sign information available in the driving scene image.

This illustration shows a response option for scenario 1 critical point 1. There is a four-lane single direction highway. It splits at the top to the left and right, with two lanes in each direction.
Figure 9. Illustration. Response option for scenario 1 critical point 1-two-lane split.

This illustration shows a response option for scenario 1 critical point 1. There is a four-lane single direction highway. There is a right-hand one-lane exit at the top, and the remaining three lanes continue straight.
Figure 10. Illustration. Response option for scenario 1 critical point 1-single exit.

This illustration shows a response option for scenario 1 critical point 1. There is a three-lane single direction highway. There is a right-hand one lane exit followed by a second one. The remaining two lanes continue straight.
Figure 11. Illustration. Response option for scenario 1 critical point 1-two exits.

. This illustration shows a response option for scenario 1 critical point 1. There is a four-lane single direction highway. There is a right-hand two-lane exit that curves to the right. The remaining two lanes continue straight
Figure 12. Illustration. Response option for scenario 1 critical point 1-two-lane exit.

This illustration shows a response option for scenario 1 critical point 1. There is a four-lane single direction highway that splits to the left and the right. The second-to-right lane is an option lane, where drivers can decide to drive to the left or right from that lane. The left splits into three lanes (which includes the option lane), and the right splits into two lanes (which includes the option lane).
Figure 13. Illustration. Response option for scenario 1 critical point 1-split with option lane.

The distribution of responses is shown in figure 14. The 107 responses are graphed based on the percentage of drivers within each age group who provided that response. Six drivers chose multiple lane combinations and were not included in the graph. In general, drivers expected to see one or two upcoming exits. These expectations were likely influenced by the exit only information above the rightmost lane since both frequent responses represent two versions of that lane exiting with either the right inside lane exiting immediately after (two-exit option) or at some time in the future (single-exit option). Older drivers were less likely to expect a split, and no older drivers chose the actual roadway geometry (split with an option lane).

This bar graph shows the booklet response distribution for scenario 1 critical point 1 with a sample size (N) of 101. Percent of drivers within age group is on the y-axis from 0 to 100 percent, and the following five categories are on the x-axis: two-lane split, single exit, two exits, two-lane exit, and split with option lane. The following three bars are depicted for each category: young, adult, and old. The percentages from left to right are as follows: two-lane split: 7.1, 13.2, and 2.4 percent; single exit: 32.1, 34.2, and 29.3 percent; two exits: 21.4, 26.3, and 39.0 percent; two-lane exit: 17.9, 10.5, and 24.4 percent; and split with option lane: 14.3, 10.5, and 0.0 percent. The percentages do not add up to 100% within groups because six drivers chose multiple lanes, and were thus not included.
Figure 14. Graph. Booklet response distribution for scenario 1 critical point 1 (number of responses (N) = 101).

Focus Group Discussions

The key themes covered during the discussion of this critical point are summarized in the following sections.

Interpretation of Sign Elements:

The sign in the first critical point was a set of two arrow-per-lane guide signs (see figure 15). The St. Helens destination was positioned over the exit only plaque.

 This photo shows guide signs associated with scenario 1 critical point 1. There are two green signs next to each other. The sign on the left has two down arrows labeled  City Ctr.-Beaverton.  Above that are labels for  405 South  and  26 West.  The sign on the right has two down arrows labeled  N.W. Ind. Area-St. Helens.  For the St. Helens arrow, two yellow signs indicate that lane is an exit only lane. The top of the sign lists 30 West as a destination. Above that, there is a sign that indicates it is Exit 3.
Figure 15. Photo. Guide signs associated with scenario 1 critical point 1.

Arrow-Per-Lane Signs:

When asked, almost all of the drivers said that the arrows referred to specific lanes. Furthermore, each arrow corresponded to a specific destination. Driver responses include the following:

Destination Information-Exit 3 and 30 West:

On the right-hand guide sign, both the sign for Exit 3 and the notation for 30 West were centered above the two downward-pointing arrows. Exit 3 was listed on a smaller, separate sign. Several drivers noticed the split between the two large guide signs and interpreted the Exit 3 sign to apply to both of the lanes on the right-hand sign. For the most part, drivers correctly interpreted this information. Driver responses include the following:

One driver was uncomfortable with the association of Exit 3 with two destinations. This may have been because the driver felt that those destinations would be served by different exits. The driver indicated that, "I believe that for Exit 3, the exit sign should be over either St. Helens or NW Indy."

The "30 West" label was centered over the two destinations/arrows, so some drivers thought that 30 West could be reached from both of the two right lanes. They indicated that, "That is a little bit confusing, but I'm thinking that 30 West is definitely available to both right-hand lanes at this point."

Some drivers continued this thought by indicating that the right-hand lanes were for two destinations, both on 30 West. Driver responses include the following:

A few drivers thought that 30 West only referred to the right-middle lane. One such driver indicated that, "I wouldn't know where St. Helens is, if it's east or west. So, I would be staying in the third lane. I know I'm on 30 West and the 30 is over the NW Industrial Area, and it's not really over St. Helens."

Exit Only:

It was less clear to drivers how the exit only indication corresponded to destination information. A few drivers provided varying opinions as follows:

Driver Expectations and Strategies:

The first critical point was located immediately before the crest on the bridge, which blocked the drivers' view of the upcoming geometry. There was no consensus about what the exit configuration would look like, and drivers described a variety of different configurations that they expected. There was also no real sense of concern because they expected to receive clarifying information closer to the exit.

Some drivers expected to see a split. Driver responses include the following:

Some drivers expected to see a dual or a two-part exit, and their responses were as follows:

Most drivers expected some sort of exit, although a few drivers expressed confusion over whether it was a one- or two-lane exit. Driver responses include the following:

A few drivers expected to receive more signs describing what would happen with the exits. Driver responses include the following:

A few drivers expected the roadway to roughly continue straight on the other side of the bridge as follows:

Challenges:

At the first critical point, drivers were mainly challenged by reading the signs. The volume of text presented as well as the lack of definition between the left and right sign panels were mentioned as challenges by some drivers as follows:

Only one driver commented about arrow-per-lane signs in general and how the arrows visually line up with lanes at this point. The driver indicated that, "This is pretty straightforward with the arrows, but sometimes in general, when I see the arrows, [I can't figure out which lane they point to]."

Improvements:

Drivers also had a number of suggestions for sign improvements. For several drivers, the first area for improvement focused on the grouping of destination information on the signs as follows:

For several drivers, the second area for improvement was the addition of distance information to the sign. Driver responses include the following:

A few drivers found that they were able to deduce some distance information from the fact that they were on the top of a bridge. One driver indicated that, "I don't know that I would anticipate a split by looking at that and being on the top of a bridge. First of all, I'm on a bridge, how many things can they do on the top of a bridge. I don't know that I would be anticipating that these would split into different directions as a result of that signage."

Scenario 1 Critical Point 2

At the second critical point, drivers saw the same signs that they did at the first critical point (see figure 16). The main difference is that drivers were then faced with a split, and the third lane became an option lane. Additionally, the lane marking between the third and fourth lanes became a solid white line.

This photo shows the driving image for scenario 1 critical point 2. There is a four-lane single direction highway. Two lanes split to the right, and three lanes split to the left. The second-to-right lane is an option lane. There is a sign that spans the three lanes splitting to the left. Each of those three lanes has a down arrow with the words  City Ctr.-Beaverton  above the arrows. The two lanes that split to the right each have a down arrow and the words  N.W. Ind. Area - St. Helens  above the arrows. There is a yellow sign indicating that the rightmost lane is an exit only lane. There is also a sign above both of these lanes labeled  Exit 3.
Figure 16. Photo. Image presented to drivers for discussion in scenario 1 critical point 2.

Key topics in the group discussion for this critical point included the following:

Response Booklet Question

At the second critical point, drivers were faced with a lane decision for 30 West. Figure 17 shows the lane options as presented in the response booklet. Lanes 3 and 4 were two legs of the same option lane. The 30 West destination was listed on a sign above lanes 4 and 5.

This illustration shows the lane numbers for lane choice decisions in scenario 1 critical point 2. There are five lanes numbered from left to right. Lanes 1 through 3 split to the left, and lanes 4 and 5 split to the right. Lanes 3 and 4 split from the same option lane. Drivers can stay in one lane and decide at the split whether to drive left or right.
Figure 17. Illustration. Lane numbers for lane choice decisions in scenario 1 critical point 2.

As shown in figure 18, the majority of drivers chose lane 4 to get to 30 West. Interestingly, older drivers were the most likely to choose lane 5, which was labeled as an exit only lane and was separated from lane 4 by a solid white line.

This bar graph shows the booklet response distribution for scenario 1 critical point 2 with a sample size (N) of 109. Percent of drivers within age group is on the y-axis from 0 to 100 percent, and the following four categories are on the x-axis: lanes 1, 2, or 3; lane 4; lane 5; and lanes 4 and 5. The following three bars are depicted for each category: young, adult, and old. The bar percentages, within category, from left to right, are: lanes 1, 2, or 3: 0.0, 7.9, and 4.9 percent; lane 4: 80.0, 68.4, and 48.8 percent; lane 5: 10.0, 10.5, and 34.1 percent; and lanes 4 and 5: 10.0, 13.2, and 12.2.
Figure 18. Graph. Booklet response distribution for scenario 1 critical point 2 (N = 109).

Focus Group Discussions

The key themes covered during the discussion of this critical point are summarized in the following subsections.

Interpretation of Sign Elements:

The signs that drivers discussed in the second critical point were the same as in the first critical point (see figure 19). The context was different, however, since drivers could clearly see the freeway split at this time. Note that because the sign was the same, driver interpretation of the sign elements is not covered in this critical point.

This photo shows guide signs associated with scenario 1 critical point 2. There are two green signs next to each other. The sign on the left has three down arrows. On the left side of the sign, there is a label for South 405. On the right side of the sign, there is a label for West 26. A label for City Ctr.-Beaverton spans the three arrows. The two lanes that split to the right each have a down arrow and the words  N.W. Ind. Area - St. Helens  above the arrows. There is a yellow sign indicating that the rightmost lane is an exit only lane. There is also a sign above both of these lanes labeled  Exit 3.
Figure 19. Photo. Guide signs associated with scenario 1 critical point 2.

Driver Expectations and Strategies:

At the second critical point, drivers were asked to make a lane choice decision for 30 West. Several drivers were uncomfortable with associating the 30 West sign element with multiple lanes. They either used other sign elements to make their decision (e.g., the exit only plaque) or tried to deduce which area (i.e., St. Helens or NW Industrial) was serviced by 30 West. Driver responses include the following:

Lanes 4 or 5:

Many drivers stated that they would choose either lane 4 or lane 5. Some of the decision factors that would help them choose a lane include keeping their options open and knowing which specific destination on 30 West they want. Driver responses include the following:

Lane 4:

Most drivers chose lane 4 to avoid the exit only lane. Driver responses include the following:

Lane 5:

However, a few drivers were uncomfortable eliminating the exit only lane and chose to be in lane 5, the rightmost lane. Driver responses include the following:

Scenario 1 Critical Point 3

As drivers came around the curve on the exit, they were faced with multiple additional sets of signs. Critical point 3 was placed at the last set of these signs right before an exit (see figure 20). Two sets of signs before this critical point (not shown) indicated to drivers that 30 West and St. Helens were in the left lanes.

This photo shows a driving image for scenario 1 critical point 3. There is a four-lane single direction highway. There are four signs shown. On the left-most sign, the top half is green and labeled  Nicolai St. West,  and the bottom half is yellow with a down arrow and is labeled  Exit Only 1/2 mile.  The second sign is green and has two down arrows. The top of the sign has a label for  30 West.  Below it and above the arrows there is a label for  St. Helens.  The third sign is green with two down arrows. The right down arrow is surrounded by a yellow box that is labeled as an exit only lane. Above both arrows, there is a label for Vaughn St. The fourth sign is a small blue sign with the letter  H  to indicate hospital.
Figure 20. Photo. Image presented to drivers for discussion in scenario 1 critical point 3.

Key topics in the group discussion for this critical point included the following:

Response Booklet Question

At the third critical point, drivers were asked whether 30 West continued over the bridge or under the bridge. This was an operationally relevant question since 30 West was their ultimate destination. At this point, the vehicle was in an option lane-the left leg led to 30 West, and the right leg led over an overpass to Vaughn Street. The lane was marked by two arrows, one for each destination. The visual perspective makes the lane direction ambiguous; however, the length of the pause at the critical point and drivers' ability to count lanes to match with destination arrows allowed most drivers to figure out that 30 West was under the bridge. Figure 21 shows the distribution of responses. Two older drivers were unsure and circled both responses. As a result, they are not included in the graph.

This bar graph shows the booklet response distribution for scenario 1 critical point 3 with a sample size (N) of 107. Percent of drivers within age group is on the y-axis from 0 to 100 percent, and the following two categories are on the x-axis: over the bridge and under the bridge. The following three bars are depicted for each category: young, adult, and old. The bar percentages, from left to right are: over the bridge: 10, 13.2, and 7.3 percent and under the bridge: 90, 86.8, and 87.8 percent. The percentages for the old group do not sum to 100 percent since some participants circled both response options.
Figure 21. Graph. Booklet response distribution for scenario 1 critical point 3 (N = 107).

Focus Group Discussions

The key themes covered during the discussion of this critical point are summarized in the following subsections.

Interpretation of Sign Elements:

The signs that drivers discussed in the third critical point were three arrow-per-lane signs (see figure 22). The option lane was indicated by the rightmost arrow on the middle  sign (St. Helens), and the leftmost arrow on the right sign (Vaughn St.). The Nicolai St. sign was the first sign where drivers encountered information about that destination.

This photo shows guide signs associated with scenario 1 critical point 3. There are four signs shown. On the left-most sign, the top half is green and labeled  Nicolai St. West,  and the bottom half is yellow with a down arrow and is labeled  Exit Only 1/2 mile.  The second sign is green and has two down arrows. The top of the sign has a label for  30 West.  Below it and above the arrows there is a label for  St. Helens.  The third sign is green with two down arrows. The right down arrow is surrounded by a yellow box that is labeled as an exit only lane. Above both arrows, there is a label for Vaughn St. The fourth sign is a small blue sign with the letter  H  to indicate hospital.
Figure 22. Photo. Guide signs associated with scenario 1 critical point 3.

Lane Destinations:

By the time drivers got to this last bank of signs, many were confused by the discontinuity of destination information that had been provided to them. Driver responses include the following:

Arrows for the Option Lane:

Several drivers were able to understand that two arrows on separate signs pointed to the same lane, the option lane for St. Helens and Vaughn Street. Driver responses include the following:

However, some other drivers had difficulty determining this. One stated that, "The fact that the left arrow on the Vaughn Street sign and the right arrow on the St. Helens sign point to the same lane is confusing. You have to deduce it yourself."

The mismatch between the number of arrows (five) and the number of lanes (four) added to the confusion for some drivers. Driver responses include the following:

Driver Expectations and Strategies:

At the third critical point, drivers encountered new destination information, which led to some confusion because the change in the destination set was unexpected.

At the second critical point, the right lane was labeled "Exit Only" and had the destination St. Helens with an arrow. After that point, the drivers rounded the corner of the two-lane exit ramp and saw another sign stating "St. Helens Left Lane," which contradicted the previous signs. At the third critical point, "Vaughn Street" was marked in the right lane and "St. Helens" was marked in the middle two lanes. This discontinuity of lane association with destination information violated some drivers' expectations. Driver responses include the following:

This change in lane destination would have upset a few drivers. Driver responses include the following:

Challenges:

At critical point 3, the driver's perspective was such that the arrows on the arrow-per-lane signs did not align, and the arrow for the option lane looked like it allowed the driver to take either branch to reach the destination 30 West. Several drivers were unsure about which lane to take. Driver responses include the following:

Many drivers were able to correctly deduce the answer given the pause in the video. Driver responses include the following:

Some drivers noted that this was sometimes a challenge with arrow-per-lane signs. Driver responses include the following:

Improvements:

Several drivers thought that canted or tilted arrows would more clearly convey that the option lane serves both St. Helens and Vaughn Street. This suggestion most frequently came from drivers in the Columbus, OH, focus groups, as they frequently encounter these types of arrows.

One implementation would have diagonal-pointing arrows on the existing option lane sign. Driver responses include the following:

One driver thought of another implementation, which would have diagonal arrows on an additional sign at the gore point. The driver indicated that, "One of the things that I've seen that helps at interchanges like this is right at the point of that "Y", they'll have a sign that says "30 West" with an arrow pointing to the left and "Vaughn Street" with an arrow pointing to the right. So that as you're coming up, you can look at it and it tells you (gestures split)."

Option Lanes in General

In critical point 2, drivers provided opinions about option lanes in general.

Positive Opinions:

Many drivers liked option lanes, especially in unfamiliar areas, because they provided more margin for error when they were not sure which lane to choose. They also felt that they had more time to make a lane decision. Driver responses include the following:

Negative Opinions:

However, some drivers preferred to avoid option lanes, if possible. One reason for this preference was driver familiarity with the interchange. Driver responses include the following:

Another reason that a few drivers gave for staying out of the option lane was to avoid drivers who use the option lane but are not sure where they are going. Driver responses include the following:

A few drivers mentioned that they would avoid option lanes when there is congestion. Driver responses include the following:

Scenario 1 Key Themes

Some of the key themes expressed in scenario 1 are as follows:

Scenario 2

Roadway Description

The roadway used in scenario 2 was primarily a sunken freeway with a limited view of the surrounding urban area. The freeway was crossed by several overpasses that limited sight distance in curves. Figure 23 shows an aerial view of the roadway.

This photo shows an aerial view of the scenario 2 roadway in Portland, OR. There is a yellow solid line highlighting the extent of the video footage. It is followed by a dashed yellow line that indicates the remainder of the intended route. The route is a long stretch of freeway, ending in a roadway split.
©2011 Google®; map annotations provded by Battelle (see "Acknowledgements")
Figure 23. Photo. Aerial view of scenario 2 roadway in Portland, OR.(37)

The extent of the video footage is shown as a solid yellow line, and the remainder of the intended route is shown as a dashed line.

Driving Objectives

Drivers were told that they were on 30 W driving in from the outskirts of town, and their objective was to get to the Portland City Center. To ensure that drivers did not think they were going to Seattle, WA (a destination that figures prominently on the signs), drivers were reminded that they were in Portland, OR. Figure 24 shows the signs that drivers encountered and the maneuvers that they had to make during the scenario drive. The relative locations of critical points are highlighted.

This illustration highlights sign information and required vehicle maneuvers in scenario 2. There is a three-lane single direction highway. The middle lane acts as an option lane at the top where the highway splits to the left and the right with two lanes in each direction. At the base of the highway, there is an arrow pointing to critical point 1. This is a set of three signs, each with an arrow pointing to a lane, the rightmost sign indicating an exit only lane. A little further up, there is a second arrow showing critical point 2. This single sign includes a diagrammatic arrow showing two lanes splitting to the left and two lanes splitting to the right. Before the split, there is an arrow pointing to critical point 3. There is one sign showing an arrow curved to the left toward Salem and another showing an arrow curved to the right toward Seattle. At the base, there is an arrow pointing to critical point 4. This is a set of four signs, each listing destinations and showing a downward arrow pointing to the lane beneath it. There is a car traveling in the middle lane. A red arrow indicates that it will use the option lane and follow to the left.
Figure 24. Illustration. Sign information and required vehicle maneuvers in scenario 2.

Scenario 2 Critical Point 1

At the first critical point, drivers approached a bank of signs mounted to an overpass (see figure 25). The vehicle was already in the correct lane for reaching the target destination.

This photo shows the driving image for scenario 2 critical point 1. There is a three-lane single direction highway with cars traveling on it. There are three green signs: one above each of the lanes. The sign on the left has a down arrow and is labeled  Beaverton Salem.  The middle sign has a down arrow and is labeled  City Center Seattle.  The sign on the right is green on the top half and is labeled  Convention Ctr. Rose Quarter.  The bottom half is yellow with a down arrow and is labeled Exit Only.
Figure 25. Photo. Image presented to drivers for discussion in scenario 2 critical point 1.

A key topic for this critical point in the group discussion was the meaning of multiple destinations listed on the same sign.

Response Booklet Question

At the first critical point for the second scenario, drivers were presented with arrow-per-lane signs with multiple destinations on each sign. Drivers were asked to select whether the signs indicated that City Center and Seattle were serviced by the same exit or whether the middle lane allowed them to reach both destinations. Figure 26 shows the distribution of responses. Five drivers either wrote in their own responses or selected both options and were not included in the figure. Most drivers thought that the middle lane would lead them to both destinations but that it did not necessarily indicate an exit.

This bar graph shows the booklet response distribution for scenario 2 critical point 1 with a sample size (N) of 111. Percent of drivers within age group is on the y-axis from 0 to 100 percent, and the following two categories are on the x-axis: same exit and middle lane. The following three bars are depicted for each category: young, adult, and old. The percentages from left to right are: same exit: 6.5, 7.9, and 19.0 percent and middle  lane: 87.1, 86.8, and 78.6 percent.
Figure 26. Graph. Booklet response distribution for scenario 2 critical point 1 (N = 111).

Focus Group Discussions

The key themes covered during the discussion of this critical point are summarized in the following subsections.

Sign Interpretation:

The signs that drivers discussed in the first critical point were three destination signs with downward pointing arrows (see figure 27). For the most part, drivers were able to obtain the key information from the signs.

This photo shows guide signs associated with scenario 2 critical point 1. There are three green signs. The sign on the left has a down arrow and is labeled  Beaverton Salem.  The middle sign also has a down arrow and is labeled  City Center Seattle.  The sign on the right is green on the top half and is labeled  Convention Ctr. Rose Quarter.  The bottom half is yellow with a down arrow and is labeled  Exit Only.
Figure 27. Photo. Guide signs associated with scenario 2 critical point 1.

Multiple Destinations:

Almost all drivers correctly interpreted the meaning of the sign where the two destinations above the arrows could be reached by taking the indicated lane.

Driver responses include the following:

Destination Order:

Some drivers also interpreted the order of the destinations as indicating the relative proximity of each destination. One driver indicated that, "I always read this as the first one [top destination] is the closest location and the last one [bottom destination] is the furthest location…and that the first one is close by but the second one is very far away."

However, there were also some other drivers who did not see the destination order as communicating relative distance. One driver indicated that, "I didn't assign any meaning to the order of the destinations. I'm new to town, looking for City Center, I see it on the sign with the arrows, so I'm going to stay in this lane. I didn't think about order-I'm scanning the signs quickly, watching for traffic around me."

Expectations and Strategies:

A few drivers were confused by the layout of the sign information. In particular, these drivers tried to assign meaning to systematic sign characteristics that they were unfamiliar with-in this case, the placement of the arrows on the right side of two of the signs. One driver commented, "Why are the arrows to the right of the signs? What are they trying to say? I'm not used to this, and it makes me wonder if it has a specific meaning."

Challenges:

A few drivers reported confusion or problems distinguishing the multiple destinations on the signs. This is certainly a potential problem with drivers who are unfamiliar with an area; however, it may have also arisen because the scenarios lacked sufficient contextual cues to clearly differentiate City Center from Seattle (i.e., no drivers from the Seattle groups had this problem since it was obvious to them that the scenario was not in Seattle). Driver responses include the following:

Scenario 2 Critical Point 2

Shortly after passing the signs in critical point 1, drivers reached the next sign (see figure 28). Drivers did not need to change lanes at this point.

This photo shows the driving image for scenario 2 critical point 2. There is a three-lane single direction highway with cars traveling on it. There is a green sign that spans all three lanes. It shows an illustration of the highway with three lanes that splits two lanes to the left and two lanes to the right. The middle lane is an option lane. The left side is labeled  5 South Salem,  and the right side is labeled  5 North Seattle.
Figure 28. Photo. Image presented to drivers for discussion in scenario 2 critical point 2.

Key topics in the group discussion for this critical point included the following:

Response Booklet Question

At the second critical point, the objective destination, City Center, was not included on the sign. Drivers were asked whether they would go north or south on Interstate 5 to reach City Center. Figure 29 shows the distribution of responses. Four drivers either stated "neither south nor north" or that they did not know. Almost all of the drivers said that they would go north to reach City Center. The listed destination for the northbound direction, Seattle, was paired with City Center on a previous sign at critical point 1.

This bar graph shows the booklet response distribution for scenario 2 critical point 2 with a sample size (N) of 105. Percent of drivers within age group is on the y-axis from 0 to 100 percent, and the following two categories are on the x-axis: south and north. The following three bars are depicted for each category: young, adult, and old. The percentages from left to right are as follows: south: 9.7, 8.3, and 9.5 percent and north: 90.3, 88.9, and 83.3 percent.
Figure 29. Graph. Booklet response distribution for scenario 2 critical point 2 (N = 105).

Focus Group Discussions

The key themes covered during the discussion of this critical point are summarized in the following subsections.

Sign Interpretation:

The diagrammatic sign indicated that the freeway will eventually split into two directions. It will also go from three lanes to two lanes in each of the north and south directions (see figure 30). The center lane is shown as an option lane that goes in both directions. Only two of the original destinations are shown on this sign.

This photo shows a guide sign associated with scenario 2 critical point 2. It depicts a four-lane single direction highway that splits to the left and right with two lanes each; the middle lane is an option lane. The left split is labeled  5 South Salem,  and the right split is labeled  5 North Seattle.
Figure 30. Photo. Guide sign associated with scenario 2 critical point 2.

Route Guidance Information:

Several drivers reported using the diagrammatic sign primarily for obtaining a high-level view of what happens at the interchange and where they need to go, but they did not particularly focus on the more detailed sign elements. Driver responses include the following:

It was also clear to several drivers that the sign indicated that there was no option to go straight. Driver responses include the following:

Information About Lanes:

Although some of the quotes listed in the previous subsection indicate that some drivers ignored the lane information provided in diagrammatic signs, many drivers used this sign element to obtain a more literal interpretation of how the lanes will transition at the interchange. Driver responses include the following:

Misinterpretation of Diagrammatic Sign Information:

Some drivers also indicated that they had difficulty determining what happens to the middle lane, or they incorrectly assumed that this lane would continue through the split. Driver responses include the following:

Expectations and Strategies:

The presentation of this diagrammatic sign after the destination sign (critical point 1) caused problems related to driver expectations for drivers because the diagrammatic sign did not provide additional information about their specific destination (City Center).

Some drivers reported becoming uncomfortable when they did not get the information they expected (i.e., where to go for City Center). Driver responses include the following:

The key outcome of the missing information about City Center was that most drivers incorrectly assumed that the grouped destinations (City Center and Seattle) shared the same direction, not just the same lane3. Driver responses include the following:

A few drivers openly recognized that they were being required to imply or guess the direction of City Center based the association between City Center and Seattle on the previous sign. This caused drivers annoyance that they had to make this assumption. Driver responses include the following:

A few drivers alluded to the concept of route continuity (i.e., the center lane to continue). In absence of other information, these drivers expected to continue on the main route and not exit. Driver responses include the following:

Challenges:

One specific challenge identified by a few drivers is that they found the switch between the arrow-per-lane and diagrammatic signs to be a source of concern. Driver responses include the following:

Improvements:

Drivers mentioned a few ways in which signage could have been improved to make it easier for them to navigate the interchange. A few drivers mentioned that distance information would have been useful for estimating how much time they had to prepare for the interchange split. Driver responses include the following:

Also, several drivers had suggestions for addressing the primary navigation challenge, which was the lack of information telling them which direction to go for City Center. Driver responses include the following:

Driver Actions:

With regard to specific driver actions, a few drivers reported that if they do not understand a sign or if they have uncertainty about the sign information, a safe strategy seemed to be to stay in the middle lane. Driver responses include the following:

Scenario 2 Critical Point 3

The third critical point was near an overpass that held two signs that provided similar information as the sign at the previous critical point (see figure 31). The roadway at this point begins curving to the right and upwards, and sight distance is limited by the overpass directly ahead and another one just beyond that one.

This photo shows a driving image for scenario 3 critical point 3. There is a three-lane single direction highway with cars traveling on it. There are two green signs: the one on the left spans the left lane and the left half of the middle lane, and the sign on the right spans the right half of the middle lane and the right lane. The sign on the left shows an arrow curving to the left and is labeled  5 South Salem.  The sign on the right shows an arrow curving to the right and is labeled  5 North Seattle.
Figure 31. Photo. Image presented to drivers for discussion in scenario 2 critical point 3.

Key topics in the group discussion for this critical point included the following:

Response Booklet Question

No response booklet question was asked for this critical point due to time constraints.

Focus Group Discussions

The key themes covered during the discussion of this critical point are summarized in the following subsections.

Sign Interpretation:

The signs at this critical point contained much of the same information as the diagrammatic sign in the previous critical point but without the lane information (see figure 32). The direction information was presented on separate signs, and this may have led to driver confusion about how to interpret the relationship between the directional arrows and the lanes on the road.

This photo shows guide signs associated with scenario 2 critical point 3. There are two green signs placed next to each other. The sign on the left has an arrow curving to the left and is labeled  5 South Salem.  The sign on the right has an arrow curving to the right and is labeled  5 North Seattle.
Figure 32. Photo. Guide signs associated with scenario 2 critical point 3.

Split Information:

For the most part, the information about the freeway split was adequately communicated by the signs. Several drivers viewed these signs as providing directional information, specifically indicating a north/south or a left/right split. Driver responses include the following:

Arrow Position:

Several drivers also tried to link arrows to specific lanes on the road even though this sometimes resulted in incorrect conclusions about what the lanes did. Driver responses include the following:

There were also a few drivers who mapped the arrows to their spatial impression of the roadway geometry. Driver responses include the following:

Timing of Split:

For a few drivers, seeing the "split arrows" repeatedly implied the imminence of the split.

Lane Markings:

The exit lane markings caused confusion for at least one driver. It was not clear which part of the split contained the actual exit.

Expectations and Strategies:

Several drivers expressed frustration about not getting the information they needed about City Center. However, based on their responses to the first sign in the scenario, most seemed to understand that the center lane would take them to City Center. This suggests that drivers became concerned if they drove extended stretches without seeing expected information. Driver responses include the following:

Scenario 2 Critical Point 4

In critical point 4, drivers encountered a bank of guide signs immediately after traversing a combination horizontal/sag-vertical curve that passed under an overpass (see figure 33). This created a blind curve that limited sight distance and the amount of time that drivers had to view the sign information. Another potential challenge to drivers was the gore point immediately ahead of them. Because the gore point occurred following a horizontal curve, drivers needed to continue steering to the left to avoid it (if they were headed to City Center).

This photo shows a driving image for scenario 2 critical point 4. There is a three-lane single direction highway with vehicles traveling on it. The lanes are shown splitting to the left and right. The middle lane is acting as an option lane, where drivers can choose to drive to the left or to the right. There are two lanes to the left and two lanes to the right. There is a green sign above each of the four lanes. The leftmost sign has a down arrow and is labeled  5 South Beaverton Salem.  The next sign also has a down arrow. The top half of the sign is brown and is labeled  OMSI.  The bottom half is green and is labeled  City Center.  The third sign has a down arrow and is labeled  5 North 30 Seattle.  Finally, the right-most sign has a down arrow. The top part of the sign is green and is labeled  Convention Ctr. Rose Quarter.  The bottom part is yellow and is labeled as an exit only lane.
Figure 33. Photo. Image presented to drivers for discussion in scenario 2 critical point 4.

Key topics in the group discussion for this critical point included the following:

Response Booklet Question

At the final critical point in scenario 2, drivers were asked five questions that all focused on whether the approach signage adequately prepared them for various dimensions of the freeway lane split. The response distribution is shown in figure 34.

Generally, drivers felt unprepared for most aspects of the split. Many of the drivers knew that a split was coming; however, few knew which lane to be in or which direction to go. One surprising result was that except for younger drivers, the majority of drivers in other age groups did not expect that they could go in both directions from the center lane despite previous signage indicating that they could. Younger drivers were also the most prepared for the split.

This horizontal bar graph shows the booklet response distribution for scenario 2 critical point 4 with a sample size (N) between 109 and 111. The top x-axis shows the percent of drivers within age group from 0 to 100 percent. The y-axis has the following five categories for young, adult, and old drivers (from top to bottom): drivers knew that a split was coming at all, drivers knew that a split was coming at that time, drivers knew which lane to be in, drivers knew that center lane could go both directions, and drivers knew which direction to go. Each bar depicts two colors: green represents adequately prepared, and red depicts not prepared enough. The green bars, from top to bottom, are: drivers knew that a split was coming at all: 80.0, 60.5, and 58.5; drivers knew that a split was coming at that time: 43.3, 39.4, and 41.5 percent; drivers knew which lane to be in: 12.9, 23.7, and 26.8 percent; drivers knew that center lane could go in both directions: 61.3, 36.8, and 33.3 percent; and drivers knew which direction to go: 20.0, 28.9, and 24.3 percent. Since there were only two response options for each category ( yes  or  no ), the percentages represented by the green and red bars in each category sum to 100 percent.
Figure 34. Graph. Booklet response distribution for scenario 2 critical point 4 (N = 109 to 111).

Focus Group Discussions

The key themes covered during the discussion of this critical point are summarized in the following subsections.

Sign Interpretation:

The signs in critical point 4 were comprised of one guide sign for each lane, including a down arrow (see figure 35). The key sign for the scenario navigation task was the left-middle sign (City Center). Also included on that sign was destination information for a local tourist attraction (the Oregon Museum of Science and Industry (OMSI)). Drivers saw another sign for this attraction earlier during the approach.

This photo shows guide signs associated with scenario 2 critical point 4. There are four signs. The leftmost sign has a down arrow and is labeled  5 South Beaverton Salem.  The next sign also has a down arrow. The top half of the sign is brown and is labeled  OMSI.  The bottom half is green and is labeled  City Center.  The third sign has a down arrow and is labeled  5 North 30 Seattle.  Finally, the right-most sign has a down arrow. The top part of the sign is green and is labeled  Convention Ctr. Rose Quarter.  The bottom part is yellow and is labeled as an exit only lane.
Figure 35. Photo. Guide signs associated with scenario 2 critical point 4.

Sign Information:

Some drivers reported that they liked the sign information but thought that the information would have been more useful if it had been provided earlier. Driver responses include the following:

Sign Reading:

Some drivers reported that when faced with the time-limited viewing conditions represented by the current critical point, their primary method of obtaining sign information would be to scan for key information. Driver responses include the following:

However, a few drivers reported that they would read from left to right. One stated, "I read these from left to right as fast as I can, and I stop reading as soon as I see what I want. Because you don't have time to read all that and make your lane change."

Expectations and Strategies:

A key challenge in the current scenario is that immediately prior to seeing the signs at this point, most drivers were prepared to follow signs for Seattle to get to City Center. This incorrect expectation was likely formed based on the destination signs at the start of the scenario and compounded by the fact that drivers received no other information about City Center until this last set of signs. Driver responses include the following:

The uncertainty leading up to the final set of signs would have also caused some drivers to feel stressed out by the split. Driver responses include the following:

Challenges:

Drivers reported multiple challenges related to reading the sign information and also with regard to the situation in general.

Sign Reading:

Many drivers identified sign elements that would have made obtaining the information they need from the signs more difficult. These challenges included too much information, mismatched expectations causing them to look for information in the wrong place, and distracting information that was not central to their navigation task. Driver responses include the following:

Many drivers also discussed the challenges caused by the geometry of the interchange, in particular, the limited sight distance and sign reading time that occur because the split happens almost immediately following a blind curve under an overpass. Driver responses include the following:

Situation-Specific Challenges to Navigating the Split:

Many drivers had comments related to several factors that made navigating the split particularly challenging. Comments on limited time include the following:

One driver commented on incorrect direction assumptions, "I didn't have a good picture of how this would turn out. Now I'm scrambling to figure out what I have to do with no time to do that. Luckily, I'm already in the [correct] lane, but I still don't like being in this situation."

Comments on multiple required subtasks include the following:

Comments on required awareness of other vehicles include the following:

Improvements:

Some drivers had ideas for improvements that would state/verify their split direction, but they generally acknowledged that the option lane was fine. Driver responses include the following:

Driver Actions:

Despite the challenges of navigating the interchange split, some drivers would try to get into the correct lane to City Center even if they were in the rightmost lane. From any lane, they would only have to maneuver over one lane or just steer to the left (if they are in the option lane). However, they acknowledged that there could be risks associated with their actions. Driver responses include the following:

One driver also commented on how driver reactions to the split had implications for safety at this location and stated, "Since these signs are only visible at the last minute, you have several drivers making decisions at the same time. Chances are someone may decide that they are in the wrong lane and try to change lanes when it's not safe to do so, and [that could lead to crashes]."

Several drivers also reported different coping strategies for similar interchange-driving situations. Driver responses include the following:

Scenario 2 Key Themes

Some of the key themes expressed in scenario 2 are as follows:

Scenario 3

Before viewing the video for scenario 3, drivers looked at a map of the area with their intended maneuver marked (see figure 36). This map helped provide some directional orientation that would normally be present if they were actually driving.

This illustration shows a map of scenario 3 roadways and maneuver. There is a solid red line that shows the route driven on the video. The line continues as a dashed line toward the destination 5 South, which is circled.
©2011 Google®; map annotations provded by Battelle (see "Acknowledgements")
Figure 36. Illustration. Map of scenario 3 roadways and maneuver.(38)

Roadway Description

The roadway was the lower deck of a bridge in Portland, OR (coincidentally, the same bridge that was driven in scenario 1). The bridge deck had four lanes, all traveling in the same direction. The bridge was fairly enclosed by support pillars on either side of the roadway. Figure 37 shows an aerial view of the roadway.

This photo shows an aerial view of the scenario 3 roadway. There is a four-lane freeway bridge deck highlighted in solid yellow that spans across a body of water and indicates the extent of the video footage. There is an arrow pointing to a left exit that then curves to the right. The curve has a dashed yellow line indicating the remainder of the intended route.
©2011 Google®; map annotations provded by Battelle (see "Acknowledgements")
Figure 37. Photo. Aerial view of scenario 3 roadway.(39)

The extent of the video footage is shown as a solid yellow line, and the remainder of the intended route is shown as a dashed line.

Driving Objectives

Drivers were told that their objective was to get onto I-5S. Figure 38 shows the signs that drivers encountered and the maneuvers that they had to make during the scenario drive. The relative locations of critical points are shown.

This illustration shows the sign information and required vehicle maneuvers in scenario 3. At the bottom of the illustration, there are two two-lane highways on the left and right that come together to form a four-lane highway. After the merge, there is an arrow pointing to critical point 1. There are three signs, each with destination listings and downward-pointing arrows to each of four lanes. The leftmost and rightmost lanes are exit only lanes. The vehicle is traveling in the second-to-right lane and must move over to the left lane for a left exit, which is marked as critical point 2. The signs at critical point 2 are the same on the left and right side of the roadway; both indicate  I-84, I-5 South, The Dalles, next left.
Figure 38. Illustration. Sign information and required vehicle maneuvers in scenario 3.

Scenario 3 Critical Point 1

After merging onto the bridge deck, drivers saw a bank of signs overhead (see figure 39). There were four lanes, with the two leftmost lanes being the continuation of a separate entrance ramp that merged onto the bridge at the same time. The lane markings for the rightmost lane indicated that it was an exit only lane.

This photo shows a driving image for scenario 3 critical point 1. There is a four-lane single direction freeway with vehicles traveling on it. There are three signs spanning over the four lanes. The sign on the left is directly over the left-most lane. The top half is green and is labeled  30 East The Dalles.  The bottom half is yellow with a down arrow and is labeled  Exit Only.  The middle sign is green and spans over the two middle lanes. There are two down arrows, and it is labeled  5 North Seattle.  The right-most sign is directly over the right-hand lane. The top part is blue and is labeled  Hospital.  The middle part is green and is labeled  Kerby Ave.  The bottom part is yellow with a down arrow and is labeled  Exit Only.
Figure 39. Photo. Image presented to drivers for discussion in scenario 3 critical point 1.

Key topics in the group discussion for this critical point included the following:

Response Booklet Question

At the first critical point for the third interchange, drivers were anticipating exit information, but their destination was not listed on any of the signs. They were asked which lane they would feel most comfortable in without sign guidance for their destination. Figure 40 shows the lane choice options as they were numbered in the response booklet.

This illustration shows the lane numbers provided in the response booklet for scenario 3 critical point 1. There are four lanes numbered 1 through 4 from left to right.
Figure 40. Illustration. Lane numbers provided in response booklet for scenario 3 critical point 1.

Figure 41 shows the distribution of responses. Most drivers were comfortable in lane 3, although a few drivers chose lane 4. There were no notable age differences between responses.

This bar graph shows the booklet response distribution for scenario 3 critical point 1 with a sample size (N) of 107. Percent of drivers within age group is on the y-axis from 0 to 100 percent, and the following six categories are on the x-axis: lane 1, lane 2, lane 3, lane 4, lanes 2 or 3, and lanes 3 or 4. The following three bars are depicted for each category: young, adult, and old. The percentages from left to right are: lane 1: 3.2, 0.0, and 0.0 percent; lane 2: 0.0, 7.9, and 13.2 percent; lane 3: 71.0, 71.1, and 71.1 percent; lane 4: 16.1, 15.8, and 13.2 percent; lanes 2 or 3: 6.5, 5.3, and 2.6 percent; and lanes 3 or 4: 3.2, 0.0, and 0.0 percent.
Figure 41. Graph. Booklet response distribution for scenario 3 critical point 1 (N = 107).

As a follow-up question, drivers were asked why they would be most comfortable in the lane that they chose. The top responses for lane 3 are as follows:

The top responses for lane 4 are as follows:

These responses are largely consistent with the discussion themes from this critical point, which are summarized following sections.

Focus Group Discussions

The key themes covered during the discussion of this critical point are summarized in the following subsections.

Sign Interpretation:

The overhead signs provided arrow-per-lane information (see figure 42). None of the signs provided any information about the drivers' destination at this point.

this photo shows guide signs associated with scenario 3 critical point 1. There are three signs next to each other. For the sign on the left, the top half is green and is labeled  30 East The Dalles.  The bottom half is yellow with a down arrow and is labeled  Exit Only.  The middle sign is green with two down arrows and is labeled  5 North Seattle.  The right sign is blue on the top and is labeled  Hospital.  The middle part is green and is labeled  Kerby Ave.  The bottom part is yellow with a down arrow and is labeled  Exit Only.
Figure 42. Photo. Guide signs associated with scenario 3 critical point 1.

The absence of information about the drivers' destination in the first bank of signs was obvious to drivers, and it prompted a variety of reactions including frustration and thinking that they may have missed their exit.

Some drivers found the destination information provided by the signs to be inadequate for getting to I-5S. Driver responses include the following:

A few drivers expressed frustration that I-5S destination information was left out while information about other destinations was provided. Driver responses include the following:

The absence of expected information made several drivers think that they had missed the exit or gotten lost. Driver responses include the following:

Expectations and Strategies:

The key expectation in this critical point is related to where drivers expected the exit to occur. Given that this information was not present in the first bank of signs encountered, drivers relied on other bases for these expectations. Some drivers expected a right-side exit based on general previous experience with interchanges. Driver responses include the following:

Several drivers reported that their expectations about which side the exit was on were based their general sense of direction. Driver responses include the following:

Some drivers formed their expectations about the direction of the exit based on the spatial relationships seen on the initial map. Driver responses include the following:

Challenges:

The sense of being in a confined space on the bottom bridge deck made a few drivers uncomfortable. Driver responses include the following:

Improvements:

Drivers had opinions about where freeway exit information should be displayed. Many of them suggested that placing the information above the eventual exit lane would be helpful. Driver responses include the following:

Many drivers suggested placing I-5S information near the I-5N information. Driver responses include the following:

Driver Actions:

Several drivers reported inherently trusting that they will get the information they need eventually (in enough time to make a decision) and that they are willing to continue down the road until they get it. Driver responses include the following:

Some drivers were prepared to exit the freeway to get better directions if necessary. Driver responses include the following:

Several drivers reported adopting a "hedging" strategy in which they stayed in the middle lane, allowing them to make lane changes if needed. Driver responses include the following:

In absence of navigation information, a few drivers used landmarks (i.e., from the map) to get a sense of the exit direction. Driver responses include the following:

A few drivers also used a similar approach to get a sense of the distance to the exit. Driver responses include the following:

Scenario 3 Critical Point 2

At this critical point, drivers encountered identical guide signs on the left and right bridge supports (see figure 43). The exit for the driver's destination (I-5S) was on the left.

This photo shows the driving image for scenario 3 critical point 2. There is a four-lane single direction freeway with vehicles traveling on it. Two green signs are seen in the distance mounted to either side of the freeway.
Figure 43. Photo. Image presented to drivers for discussion in scenario 3 critical point 2.

Key topics in the group discussion for this critical point included the following:

Response Booklet Question

At the second critical point, drivers viewed side-mounted guide signs that indicated I-5S and "The Dalles" would be exiting to the left. They were asked what surprised them about the required maneuver. The responses were categorized into seven categories, which were then ranked by response frequency (see table 7).

Table 7. Rank of booklet responses for scenario 3 critical point 2 (N = 92).

Rank

Description of Element

1

Left exit: Drivers did not expect a left exit. Many based this expectation on the map provided.

2

New information: Drivers received no previous indication of I-5S.

3

Destination consistency: The Dalles, 30E, I-84, and I-5S all had changing associations on the signs.

4

Sign placement: Previous signs were overhead, but these signs were on the sides, and the symbols were not very visible.

5

Redundant signage: Both signs provided the same information.

6

Sign on right: The nearest sign was located on the right side of the freeway for an exit on the left.

7

Quick lane changes: Drivers were being required to make multiple lane changes over a short distance.

The most commonly mentioned surprising element was that the exit was on the left. This surprised drivers for two reasons: (1) the map set up their initial expectation for a right exit and (2) most exits are on the right-hand side of the roadway. The next two most common responses relate to the destination information provided-that there was no previous indication of I-5S and the inconsistency of the destinations provided between the various sets of signs. Drivers were also surprised by sign placement and that the same sign information was in two different locations. The third most frequently reported surprising element was how little time drivers had to get over to the exit lane at that point.

Focus Group Discussions

The key themes covered during the discussion of this critical point are summarized in the following subsections.

Sign Interpretation:

The guide signs on either side of the roadway provided the first information to drivers about the location of their exit, which was on the left (see figure 44). The I-5S information was provided with other destination information and was not as easy to see as the other elements.

This photo shows a guide sign associated with scenario 3 critical point 2. It is green and labeled  85 5 South The Dalles Next Left.
Figure 44. Photo. Guide sign associated with scenario 3 critical point 2.

Sign Placement:

Many drivers expected better consistency with regard to the placement of consecutive signs. Driver responses include the following:

Some drivers had concerns about the possibility of missing signs because of low visibility or occlusion by other vehicles. Driver responses include the following:

A few drivers observed that sign visibility could be reduced because they exist outside the normal field of view. Driver responses include the following:

Sign Information/Elements:

Some drivers expected information about major destinations or freeways to be prominently displayed and that the I-5S symbol was not only small, but also overshadowed by other sign information. Driver responses include the following:

Some drivers also reported some confusion caused by seemingly unnecessary or unexpected information elements as follows:

Redundant Signs:

Some drivers also felt that providing two identical signs was potentially more of a distraction than a benefit. Driver responses include the following:

Expectations and Strategies:

Some drivers would have expected that being in the right middle lane was the most logical choice, given the lack of useful guidance information. Driver responses include the following:

Several drivers expected and would have liked to receive distance information to help them decide whether to attempt the multiple lane changes. Driver responses include the following:

Driver Actions:

Drivers reported that they would respond to last-minute multiple lane changes in a variety of different ways, often depending on the driving conditions. Some drivers reported that they would slow down to give themselves more time to execute the maneuver, while others hoped that adjacent drivers would let them into the lane. Driver responses include the following:

Most drivers would attempt to get to the exit if traffic was light enough. Driver responses include the following:

A few other drivers acknowledged the challenges caused by other traffic. Driver responses include the following:

There were also a few drivers who would just keep going to I-5N, turn around, and get onto I-5S coming back. Driver responses include the following:

A few drivers recognized that they simply would not have made the exit. Driver responses include the following:

Multiple Lane Changes in General:

Drivers also provided opinions about multiple lane changes at interchanges in general. In particular, they recognized several considerations that would influence whether or not they would decide to make a lane change.

Influencing Factors:

Many drivers reported being influenced by whether or not traffic volume and speed allowed for multiple lane changes. Driver responses include the following:

Several drivers described the safety-related considerations of making multiple lane changes. Drive responses include the following:

A few drivers considered the distance available.

Challenges:

Drivers also identified several factors that can make multiple lane changes more challenging. A few drivers felt that multiple lane changes to the left were more challenging than to the right. Driver responses include the following:

A few drivers mentioned the influence of other merging drivers. Driver responses include the following:

One driver noted that poor weather increases the difficulty level and stated, "Rain and poor weather would also make it harder."

Also, one driver mentioned that unfamiliarity with the interchange or driving at night would make the maneuver more challenging. The driver indicated that, "[Multiple lane changes] are challenging, especially if you don't know where you're going, or you're unfamiliar with the area, or it's at night."

Several drivers commented on how stressful they perceive multiple lane changes to be. Driver responses include the following:

A few drivers also found multiple lane changes effortful. Driver responses include the following:

A few drivers also reported a general dislike of multiple lane changes. Driver responses include the following:

A few other drivers reported going out of their way to avoid interchanges with multiple lane changes. Driver responses include the following:

Scenario 3 Key Themes

Some of the key themes expressed in scenario 3 are as follows:

Task 4 Conclusions

Drivers expected that there would be functional relationships between lanes on the roadway and arrows/text on signs and that the signs themselves would make these relationships clear. For example, when looking at signs with arrow-per-lane information, drivers interpreted the arrows as corresponding to information that was directly above or grouped somehow with the arrows. In scenario 1, this led to an unnecessarily restricted view of which destinations were served by each lane. This tendency to look for relationships also occurred with other sign information such as route shields and exit only plaques. Additionally, option lane arrows created more work for drivers since they had to discern that multiple destinations could be reached by a single lane, which branched into different directions.

Drivers expected that the distance between a guide sign and a final (or last chance) decision point would be sufficient to allow for making any necessary lane changes in a safe and timely manner. Moreover, drivers utilized distance information for upcoming exits so that they knew how much time they had to make a lane change.

Drivers expected that they would have more than one opportunity to obtain necessary destination and lane information before they needed to make a final decision regarding lane choices. A second opportunity to see the same information may also serve as a confirmation for drivers. Unfamiliar drivers in particular may appreciate feedback that they are in the correct lane or have not missed their exit.

Drivers expected that that the freeway system would provide them with the necessary information to construct a mental model and that it would be sufficient to support timely and accurate decisions about lane choice. Drivers seemed to actively create a mental model of the interchange as they drove through it. If they were missing information that they needed, they may have adopted a "wait and see" attitude, making assumptions about the missing information or filling in the information using supplementary information that was available about the area (e.g., cardinal directions, landmarks, etc.). Drivers generally trusted that the information that they needed would be provided to them in enough time to act.

Drivers expected that the information available to them through the freeway system would be sufficient to support decisions about lane choices so that they would never have to move over more than one lane at the last moment. Drivers trusted that they would get the information that they needed in a timely manner. However, in the face of uncertainty or unfamiliar surroundings, some drivers adopted a strategy of staying in an option lane where it would be easy to change into other likely destination lanes. This shows a tradeoff between increasing the likelihood of making one lane change while decreasing the likelihood of making multiple lane changes. Other drivers preferred the certainty associated with using exit only lanes.

Drivers expected that the freeway system would provide sufficient information to support decisions about all route choices, not just frequent or popular choices. Drivers tended to have an egocentric view of destination information; they want their destination information to be clear. Additionally, when the set of destinations listed on a sign changed (destinations were added or removed from a series of guide signs), drivers became uneasy.


2The focus groups were planned under the assumption that no more than nine participants could be included in any one session. This limit was relaxed, yet the overall plan still reflected the initial number.

3Note that it is possible that the association between City Center and Seattle was influenced by drivers answering the response booklet question for this critical point. In particular, that question asked drivers to specify a direction for City Center, which may have implicitly caused them to assign the Seattle direction to City Center when they may have otherwise remained more neutral about this until they received more information.

 

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United States Department of Transportation - Federal Highway Administration