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Publication Number:  FHWA-HRT-15-067    Date:  August 2015
Publication Number: FHWA-HRT-15-067
Date: August 2015



Breakthroughs in Vision and Visibility for Highway Safety Workshop Summary Report - August 13-14, 2014

Part Two: Discussion


Expert Panel Discussion

At the end of the first day, the presenters participated in a panel discussion and answered questions from the other workshop participants. The workshop participants directed general questions to all five presenters and also posed specific questions to individual presenters for their response. A summary of the panel discussion is outlined in the following sections.

Luminance and the Effect of Speed on Crash Rate 

The panelists noted that when traveling on high-speed roads (e.g., interstate highways), the major visual task for the driver is to be aware of the vehicles ahead. More light is needed on slow-speed roads because of complexities (e.g., intersections and narrow and winding road curvature) associated with such roads. According to the panelists, older drivers tend to decrease the time they spend driving on unfamiliar or high-speed roads at night. In terms of visual capabilities, the panelists suggested that younger drivers have limited experience but have the best vision, whereas older drivers have the most experience but have impaired vision. The panelists mentioned that there is a gap in research in how changes in roadway infrastructure affect drivers familiar with the roadway and that there are various elements that could be included in the redesign to address this issue.

Driver Behavior and Visibility Effects from Glare

During the discussion, the panelists noted that there are hours of eye-glance data that need to be mined from the second Strategic Highway Research Program's naturalistic driving study. The panelists also highlighted that the California DOT (i.e., CALTRANS) is currently expanding its research on managing lanes. CALTRANS do not want to put up glare screens or glare walls and are investigating how much lighting could be installed to help drivers avoid looking at the glare of oncoming vehicles.

The panelists mentioned that researchers for a study conducted over a 3-year period in Finland collected data from drivers in high-speed and low-speed situations (Kallberg, 1993). Halfway through the experiment, the researchers installed reflector posts. In the high-speed situation, they observed no difference in driver behavior; however, in the low-speed situation, the reflectorization resulted in an increase in crash rates because drivers maintained a higher speed even though the road was complex. Researchers for this study theorized that reflector posts created a false sense of safety. This meant that drivers felt that they could keep their speeds high instead of decreasing them to appropriately and safely maneuver through the terrain.

Virtual Windshield and Driver Perception

The panelists spent part of the discussion focusing on virtual windshields and driver perception. They noted that the HUD reduces a driver's peripheral vision and acuity. Moreover, it can even create a hazard by inhibiting the driver's ability to refocus when the image being broadcast onto the screen brings his or her attention "in" instead of "out" (e.g., viewing the world outside of the vehicle). The panelists suggested that this may be worse than looking at the instrument cluster in a vehicle's dashboard. They also noted that the use of these virtual windshields is becoming more widely available. There is new technology moving toward interconnected vehicles and infrastructure that is leading the way for these windshields to project traffic signs and speed limits directly in the driver's immediate field of view. According to the panelists, this creates an increase in information workload and a new environment that the driver needs to adjust to. There is a significant need for human factors research and involvement to ensure high levels of safety with the emergence and adoption of these new technologies.

The panelists mentioned that there are individual differences when it comes to a person's ability to focus and respond to visual information. For example, when the driver has two sets of information (i.e., the projected and the real-world view), the human eye needs to choose which set of information to focus on. When there are two surfaces, including one that is transparent to the other view, people tend to choose to focus on the closest surface. In this scenario, that would be the information projected on the virtual windshield. Panelists noted the importance of a low contrast between surfaces when there is low illumination because there is less ability for the human eye to clearly focus on a specific view.

Gaps in Human Factors Visibility Research

The panelists also discussed gaps in human factors visibility research. They noted that the interaction between cars and connectivity is an important innovation, particularly in terms of driver perception. Vehicles will be able to send messages to other vehicles without any dependence on conditions. This is because intervehicle communication relies on established infrastructure, including lights, signs, markings, and sounds (e.g., horns). The panelists suggested that the loop needs to be closed between visibility devices and the capabilities of different drivers. More specifically, individual differences need to be studied and accounted for to ensure that these new visibility technologies can adapt to a wide variety of drivers. The panelists mentioned that researchers should study young, old, experienced, and novice drivers, and analyze their varying visibility requirements and mental capacity to understand the world around them.

According to the panelists, the infrastructure currently available encompasses the environment as a system of parts. These parts (e.g., street signs, traffic lights, and lane markings) are not "interconnected," but they work together to ensure safe highway and roadway travel. The panelists mentioned that one goal is to tighten up this system of parts by taking inputs from vehicles as part of future Intelligent Transportation System installations to form a cohesive system. During the discussion, the panelists also noted that researchers have previously conducted studies to analyze the effects of lighting on driver performance to model behaviors. The researchers focused on the direction of drivers' vision and which components of the visual system aided or inhibited a driver's visible acuity. When considering visibility and interconnectivity as a whole system, the panelists suggested that information silos need to be identified and broken down. The panelists put forward two specific questions that need to be answered: (1) does really good retroreflectivity mean that more or less lighting is needed; and (2) is it a better investment for municipalities to install dimmable systems that can be increased or decreased in energy consumption, rather than repainting pavement markings every 3-6 months?

The panelists agreed that there needs to be a better systematic approach to nighttime visibility. For example, the geometries for daytime visibility are different for pavement markings, retroreflectivity, signs, and raised pavement markings. The panelists suggested that research needs to be focused on identifying other performance metrics given that nighttime visibility is integrated. In addition, they agreed that nighttime visibility needs to be better defined, because current research is based on daytime conditions and assumptions. Although driver behavior, specifically in regard to speed, does not generally change between day and night driving, there are many other things that do change at night that are not documented in the MUTCD. The panelists highlighted that local and State governments are looking for objective performance data to justify new lighting infrastructure or to maintain existing surface infrastructure. At this time, it is not known if it is more cost-effective to spend money to install dimmable lighting or to spend money on maintaining existing pavement markings.

Smart Vehicle Technology

The panelists went on to discuss smart vehicle technology. With new "smarter" technology becoming increasingly more available (e.g., rear-visibility cameras, lane-keeping assist, and blind-spot monitoring), the panelists asked why accidents are still happening. They questioned what it is that the human element in this mix is failing to do and asked if onboard data recorders could be used to examine vehicle crashes after the fact and determine the fault. Panelists suggested that augmented systems could possibly help identify this missing link. They agreed that further research is needed to identify the shortfalls of these technologies and to find solutions to enhance their effect on safety.


Breakout Group Discussions

Potential Research Topics and Critical Questions

For the second half of this workshop, workshop participants split into two small groups to brainstorm and answer two different, but related, topics. The first session charged the groups to answer the questions, "What exploratory research do we need to do to get us to the future, and how do we coordinate across disciplines?" While the groups had the charge to consider exploratory and cross-disciplinary research, the discussion for the most part was on applied research with a narrower highway focus.

Session One:
What exploratory research do we need to do to get us to the future, and how do we coordinate across disciplines?

Session Two:
Needed Applied Research and Next Steps

The second session focused on identifying and creating concrete next steps to move research toward addressing the ideas discussed in the first brainstorming session. These are outlined in the following sections.

  1. Adopt FHWA Visibility Vision Statement and Goals
    Workshop participants said that FHWA has the potential to facilitate the focus of upcoming research by producing a vision statement. The direction set by this statement includes quantification of safety measurements and acceptance of new technology, and enables FHWA to react efficiently to new technology as it is introduced and available to the public. The group proposed a draft vision statement as a consensus of the different suggestions discussed. This vision statement communicates research objectives across infrastructure, vehicle, and user as follows:

    FHWA Vision - To provide the safest and most cost-effective visual  environment for all users through full integration of infrastructure and  technology.

  2. Create a Framework for FHWA's Visibility Research
    The workshop participants proposed a framework (figure 5) in support of the aforementioned vision statement that identifies three main research components: infrastructure, vehicle, and user. Among the three components, workshop participants said that infrastructure is the component over which FHWA has the most influence. This framework correlates factors that can be controlled by researchers and practitioners and can be used as a reference to identify research needs.

    Figure 5 indicates consistent standards across infrastructure, vehicles, and users and consistent communications systems across infrastructure, vehicles, and users. Under this research framework, workshop participants suggested that projects in the next 5 years perform a benefit cost analysis and assess the effect a study will have on vehicle-to-infrastructure and V2V communications.

    A diagram shows a proposed framework for visibility research. At the top of the chart is box labeled vision. This flows into a shaded standards section, with individual boxes for infrastructure, vehicle, and user. From here, each of the three boxes flows into the shaded communication systems section. Infrastructure leads into lights, signs, markings, base map, road geometry, and complexity of scenario. Vehicle leads into lighting, sensor technology, fleet turnover, and display. User flows into capabilities, acceptance, education, training, and license.
    Figure 5.  Proposed framework for visibility research.

  3. Develop a Clearinghouse of Research in Other Disciplines and Countries
    Workshop participants suggested that a framework that brings together research and information is needed. The strategic program for visibility should include stakeholders and agencies that could contribute their respective research and help define uniform safety measurements and correlation factors. The workshop participants said that this research plan needs to be promoted to obtain inputs from stakeholders and to refine research needs based on visibility. Participants mentioned that a clearinghouse could be developed of relevant vision, human cognition and perception, and vehicle automation technology research. The workshop participants suggested the following list of key potential stakeholders:
    • Transportation Research Board's Standing Committee on Visibility.
    • American Association of State Highway and Transportation Officials.
    • National Highway Traffic Safety Administration.
    • Intelligent Transportation Systems Joint Program Office.
    • FHWA Resource Center Innovative Finance Team.
    • Academia.
    • Automotive Industry (Alliance of Automobile Manufacturers and Japanese Automobile Standards Internationalization Center).
    • Association for Unmanned Vehicle Systems International.

  4. Explore Driver, Pedestrian, and Night Simulation Training
    Workshop participants discussed limitations in previous simulator research, specifically night simulation and pedestrian and driver interaction simulation. IFSTTAR has conducted some pedestrian and nighttime research, but workshop participants suggested that more is needed to understand driver behavior in the decision-making process, particularly when there is limited visual acuity, and to test new technologies.

  5. Identify Infrastructure Investments
    During the discussion, workshop participants said that investment in new types of highway infrastructure may be needed over the next 20 years. They suggested that new infrastructure may be inclined toward automated driving and will incorporate vehicle and infrastructure sensors that do not rely on human vision but on machine-vision systems. Workshop participants mentioned that long-term investments should focus on providing the infrastructure elements and technology that will complement the entire integrated system.

  6. Investigate and Establish the Effectiveness of Retroreflectivity
    Workshop participants discussed technologies that are already influenced by FHWA, including monitoring the driver and enhancing the visibility of the road through retroreflectivity and lighting. Given that the effectiveness of retroreflectivity and lighting is not currently known, workshop participants said that more research needs to be conducted. This will help to determine whether there is a correlation between retroreflectivity, lighting, and a particular scenario of interest. Workshop participants suggested that FHWA could play a role as a facilitator and ensure roadways remain a focus of research.

  7. Update MUTCD and the Highway Safety Manual
    The final research area discussed by workshop participants related to how Congress mandates safety performance measures and crash-modification factors. These are used as predictive tools to guide expectations regarding reductions in crashes. Workshop participants mentioned that this requirement funds research based on the financial investment of the infrastructure. Participants highlighted that States have been charged with performance-based decisionmaking, whereas researchers use the available data to create these standards, even if they are not complete or of high quality. Workshop participants suggested that a next step would be to redefine and reestablish the minimum safety requirements set within the MUTCD and Highway Safety Manual using new technology specifications. They said that this type of research is an initial point, or a datum, for research over the next 5 years.



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