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Publication Number: FHWA-HRT-06-033
Date: August 2006

Task Analysis of Intersection Driving Scenarios: Information Processing Bottlenecks

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Figure 1. An outline diagram showing organization of components of each scenario analysis.

Scenario 1 (followed by bulleted list)

Scenario description and assumptions

Scenario diagram

Scenario timeline

Task analysis table

Segment analysis (followed by two subheads)

Segment 1

Segment task analysis table (end bulleted list)

1. Task 1 (followed by a list of six items)

1. Perception subtask 1 and workload estimate

2. Cognitive subtask 1 and workload estimate

3. Psychomotor subtask 1 and workload estimate

4. Perceptual subtask N and workload estimate

5. Cognitive subtask N and workload estimate

6. Psychomotor subtask N and workload estimate

2. Task N (followed by 4 bulleted items)

Approximate task duration and sequence within segment timeframe

Potential contributions to high workload and information processing bottlenecks and mitigation factors

Task pacing and timing

Segment (a subhead to Task N)

Scenario-wide analysis

Scenario N

Return to Figure 1

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Figure 2. Diagram. Example scenario plan diagram identifying key assumptions.

Example scenario diagram which shows a plan view illustration of the scenario and identifies the key assumptions. Street intersection with the following driving task segments shown: approach, deceleration, intersection entry, prepare to turn and execute turn. A vehicle approaches the intersection and turns left at a green light.

Return to Figure 2

Figure 3. Diagram. Two-page layout of segment analysis showing key components.

Page on left has segment task workload estimate tables and discussion of segment assumptions and other key points. Page on right has segment diagram, relative timing and duration of segment tasks, summary of contributions to bottlenecks and mitigating factors, and discussion of task pacing and sequencing.

Return to Figure 3

Figure 4. Scenario Diagram. Scenario 1–Left Turn on Green Light diagram, details, and assumptions.

Street intersection with the following driving task segments shown: approach (approximately 50 kilometers per hour), deceleration (50 to 0 kilometers per hour), intersection entry (approximately 0 kilometers per hour), prepare to turn and execute turn (0 to 50 kilometers per hour). A vehicle approaches the intersection and turns left at a green light.

Return to Figure 4

Figure 5. Line Graph. Scenario 1–Left Turn on Green Light timeline depicting key segment phases duration and event/task milestones.

X axis equals time with task segments and task milestones marked along the axis. Y axis equals speed in kilometers per hour. Line describes speed during driving segments and at event/task milestones. The approach is at 50 kilometers per hour and drops off quickly to 0 during the deceleration stage. The line stays at 0 with a slight bump to indicate possible slight accelerations during intersection entry. Prepare for turn stages is at 0 kilometers per hour. The line moves upward rapidly to 38 kilometers per hour to account for acceleration during execution of the turn.

Return to Figure 5

Figure 6. Scenario Diagram. Scenario 1–Left Turn on Green Light Approach segment scenario diagram.

Diagram of intersection highlighting the approach segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. This includes the roadway in front of the vehicle, the intersection, the crosswalk, pedestrian light, and traffic light.

Return to Figure 6

Table 7.

Scenario 1–Left turn on green light Approach segment relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

1.1.1 Maintain safe lane position is a forced-paced task that continues from start to finish.

1.1.2 Check surround for unsafe situations is a self-paced task that continues from start to finish.

1.1.3 Decelerate is a self-paced task self-paced task that takes place only at the start.

1.1.4 Identify intersection characteristics self-paced task takes place after decelerate.

1.1.5 Observe status of light self-paced task that takes place primarily at the same time as decelerate, but is initiated before and for a short time after.

1.1.6 Determine if the light is about to change self-paced task that takes place after the previous two and is half way through the scenario's timing.

1.1.7 Identify intersection as correct turn intersection is a forced-paced task that takes place near the end after determining if the light will change.

1.1.8 Activate turn signal is a forced-paced task that ends the scenario.

Return to Table 7

Table 9.

Scenario 1–Left turn on green light Deceleration segment relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

1.2.1 Maintain safe lane position is a forced-paced task that takes place from start to finish.

1.2.2 Check surround for unsafe situations is a self-paced task that takes place from start to finish.

1.2.3 Begin deceleration is a forced -paced task that takes place just at the start.

1.2.4 Observe vehicle stopping trajectory is a self-paced task that takes place after deceleration is begun and throughout the rest of the task.

1.2.5 Maintain safe distance from decelerating following vehicle is a self-paced task that takes place after deceleration is begun and throughout the rest of the task.

1.2.6 Observe status of light is a self-paced task that takes place primarily near the end of the timeframe, but is carried out throughout the tasks.

Return to Table 9

Figure 7. Scenario Diagram. Scenario 1–Left Turn on Green Light Deceleration Segment scenario diagram.

Diagram of intersection highlighting the deceleration segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. This includes the intersection, stop line, crosswalk, and traffic light.

Return to Figure 7

Figure 8. Scenario Diagram. Scenario 1–Left Turn on Green Light Intersection Entry segment scenario diagram.

Diagram of intersection highlighting the intersection entry segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. This includes the lead and following vehicles, the traffic light, and the vehicles to the left and right waiting in cross traffic lanes.

Return to Figure 8

Table 11.

Scenario 1–Left Turn on Green Light Intersection Entry segment relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum.

1.3.1 Wait for lead vehicle to turn is a self-paced task that takes place through the first half of the timeframe.

1.3.2 Observe status of light is a self-paced task that takes places from start to end.

1.3.3 Check for conflicts with following vehicle is a self-paced task that takes place from start to end.

1.3.4 Check for red-light- running cross traffic is a self-paced task that takes place three-quarters of the way through the task.

1.3.5 Advance into intersection is a self-paced task that takes place at the end of the task.

Return to Table 11

Figure 9. Scenario Diagram. Scenario 1–Left Turn on Green Light Prepare for Turn segment scenario diagram.

Diagram of intersection highlighting the prepare to turn segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. This includes the crosswalk to the left (where the vehicle will turn), the following vehicle, two vehicles approaching in oncoming traffic lanes, and the traffic signal.

Return to Figure 9

Table 13.

Scenario 1–Left Turn on Green Light Prepare for Turn segment relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum. All four tasks are forced-pace and take place from start to end. They are:

1.4.1 Look for gap in traffic

1.4.2 Observe status of light

1.4.3 Check for hazards in turn path

and 1.4.4 Check for conflicts with following vehicle.

Return to Table 13

Figure 10. Scenario Diagram. Scenario 1–Left Turn on Green Light Execute Turn segment scenario diagram.

Diagram of intersection highlighting the execute turn segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. This includes the crosswalk through which the which the turned vehicle will pass, the lead vehicle now in front of the turned vehicle, and the two cars in oncoming traffic.

Return to Figure 10

Table 15.

Scenario 1–Left Turn on Green Light Execute Turn segment relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

1.5.1 Accelerate to initiate turn is a forced-paced task that takes place during the first half of the total timeframe.

1.5.2 Steer into turn is a forced-paced task that takes place during the first half of the total timeframe.

1.5.3 Check for hazards in turn path is a forced-paced task that takes place during the first half of the total timeframe.

1.5.4 Continue accelerating up to speed is a self-paced task that takes place during the second half of the total timeframe.

1.5.5 Maintain safe lane position is a forced-paced task that takes place during the second half of the total timeframe.

1.5.6 Maintain safe distance from accelerating lead vehicle is a self-paced task that takes place during the second half of the total timeframe.

1.5.7 Check surround for unsafe situations is a self-paced task that takes place during the second half of the total timeframe.

Return to Table 15

Figure 11. Line Graph. Scenario 1–Left Turn on Green Light total estimated workload ratings for all tasks in each segment.

This graph shows the overall level of workload associated with a segment. X axis itemizes task segments: approach, deceleration, intersection entry, prepare to turn, and execute turn. Y axis equals estimated workload ratings from 0 to 35. One line (solid) describes workload peaks for perceptual subtasks, a second line (solid, then broken) describes workload peaks for cognitive subtasks, and a third line (dotted) describes workload peaks for psychomotor subtasks. The line for the perceptual and cognitive subtasks follow a similar track in workload rating. The psychomotor skills are rated much lower and stay lower than the other two during preparation to turn and execute turn. Intervals containing nonroutine forced-paced tasks are shaded in orange.

Return to Figure 11

Figure 12. Line Graph. Scenario 1–Left Turn on Green Light average estimated workload ratings per task for each scenario segment.

This graph shows the average level of workload associated with a segment. X axis itemizes task segments: approach, deceleration, intersection entry, prepare to turn and execute turn. Y axis equals estimated workload ratings from 0 to 35. One line (solid) describes workload peaks for perceptual subtasks, a second line (solid, then broken) describes workload peaks for cognitive subtasks, and a third line (dotted) describes workload peaks for psychomotor subtasks. Intervals containing nonroutine forced-paced tasks are shaded in orange. This graph generally represents the overall level of "difficulty" associated with the tasks in a segment. The perceptual subtasks and cognitive subtasks track similarly with the exception of greater workload required by the perceptual subtasks during the approach interval. Intervals containing nonroutine forced-paced tasks are shaded in orange.

Return to Figure 12

Figure 13. Scenario Diagram. Scenario 2–Left Turn on Yellow Light diagram, details, and assumptions.

Street intersection with the following driving task segments shown: approach, deceleration, decision to proceed, intersection entry and execute turn. A vehicle approaches the intersection and turns left on a yellow light. Speeds in each of the segments are as follows: Approach, approximately 50 kilometers per hour; deceleration, 50 to 40 kilometers per hour; decision to proceed, 40 to 20 kilometers per hour; intersection entry 20 to 16 kilometers per hour; and execute turn, 16 to 50 kilometers per hour.

Return to Figure 13

Figure 14. Line Graph. Scenario 2–Left Turn on Yellow Light timeline depicting key segment phases duration and event/task milestones.

X axis equals time with task segments and task milestones marked along the axis. Y axis equals speed in kilometers per hour. Line describes speed during driving segments and at event/task milestones. The graph shows the change in speed during the approach through execution of the turn. It starts at 50 kilometers per hour, drops quickly to 16 kilometers per hour during intersection entry and then rises to 50 kilometers per hour through execution of the turn.

Return to Figure 14

Figure 15. Scenario Diagram. Scenario 2–Left Turn on Yellow Light Approach segment scenario diagram.

Diagram of intersection highlighting the approach segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks.

Return to Figure 15

Table 21.

Scenario 2–Left Turn on Yellow Light Approach segment relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

2.1.1 Maintain safe lane position is a forced-paced task that lasts from start to end.

2.1.2 Check surround for unsafe situations is a self-paced task that lasts from start to end.

2.1.3 Decelerate is a self-paced task that takes place at the very start.

2.1.4 Identify intersection as correct turn intersection is a self-paced task that takes placed after deceleration.

2.1.5 Identify intersection characteristics is a self-paced task that takes placed after intersection is identified as correct, and it is half way through the continuum.

2.1.6 Activate turn signal is a self-paced task takes placed four-fifths of the way through the continuum, but can expand to slightly before or after this point.

2.1.7 Observe status of light is a self-paced task can take place during the complete timeframe but primarily coincides with the activation of the signal.

2.1.8 Determine if the light is about to change is a self-paced task comes at the end of the timeframe.

Return to Table 21

Figure 16. Scenario Diagram. Figure 16. Scenario 2–Left Turn on Yellow Light Deceleration segment scenario diagram.

Diagram of intersection highlighting the deceleration segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks.

Return to Figure 16

Table 23.

Scenario 2–Left Turn on Yellow Light Deceleration segment relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum.

2.2.1 Maintain safe lane position is a forced-paced task that lasts from start to end.

2.2.2. Check surround for unsafe situations is a self-paced task that lasts from start to end.

2.2.3 Begin deceleration is a forced-paced task that takes place just at the start.

2.2.4 Observe vehicle deceleration trajectory is a self-paced task that follows the beginning of deceleration and lasts through the end.

2.2.5 Maintain safe distance from decelerating following vehicle self-paced task that parallels observation of vehicle deceleration trajectory and lasts through the end

Return to Table 23

Figure 17. Scenario Diagram. Scenario 2–Left Turn on Yellow Light Decision to Proceed segment scenario diagram.

Diagram of intersection highlighting the decision to proceed segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. These include the following vehicle, crosswalk directly in front of the vehicle, the stop line, traffic light, and pedestrian lights.

Return to Figure 17

Table 25.

Scenario 2–Left Turn on Yellow Light Decision to Proceed segment relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

2.3.1 Maintain safe lane position is a forced-paced task that lasts from start to end.

2.3.2 Check surround for unsafe situations is a self-paced task that lasts from start to end.

2.3.3 Observe vehicle deceleration trajectory is a self-paced task that lasts from start to end.

2.3.4 Maintain safe distance from decelerating following vehicle is a self-paced task that lasts from start to end.

2.3.5 Observe status of light is a forced-paced task that takes place in just the beginning of the timeline.

2.3.6 Determine if stopping will conflict with following vehicles is a forced-paced task that takes place in the latter two-thirds of the timeline.

2.3.7 Determine if stop can be made before intersection is a forced-paced task that takes place in the latter two-thirds of the timeline.

Return to Table 25

Figure 18. Scenario Diagram. Scenario 2–Left Turn on Yellow Light Intersection Entry segment scenario diagram.

Diagram of intersection highlighting the intersection entry segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. These include the traffic behind the vehicle, all crosswalks, the traffic light, and traffic approaching from all directions.

Return to Figure 18

Table 27.

Scenario 2–Left Turn on Yellow Light Intersection Entry segment relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

2.4.1 Maintain safe lane position is a is a forced-paced task that lasts from start to end.

2.4.2 Check surround for unsafe situations is a self-paced task that lasts from start to end.

2.4.3 Decelerate to turning speed is a forced-paced task that lasts from start and three-quarters of the through the timeline.

2.4.4 Check for conflict with following vehicle is a self-paced task that lasts from start to end.

2.4.5 Check for red-light- running cross traffic is a forced-paced task that lasts from start and three-quarters of the through the timeline.

2.4.6 Confirm that oncoming vehicles are stopping is a forced-paced task that lasts from start and three-quarters of the through the timeline.

2.4.7 Check for hazards in turn path is a forced-paced task that lasts from start and three-quarters of the through the timeline.

2.4.8 Continue into intersection is a forced-paced task that takes place only in the last one-quarter of the timeline.

Return to Table 27

Figure 19. Scenario Diagram. Scenario 2–Left Turn on Yellow Light Execute Turn segment scenario diagram.

Diagram of intersection highlighting the execute turn segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. This includes checking for hazards in the turn path and maintaining safe position in relation to any traffic in front.

Return to Figure 19

Table 29.

Scenario 2–Left Turn on Yellow Light Execute Turn segment relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

2.5.1 Accelerate to initiate turn is a force-paced task that lasts for the first half of the timeline.

2.5.2 Steer into turn is a force-paced task that lasts for the first half of the timeline.

2.5.3 Check for hazards in turn path is a force-paced task that lasts for the first half of the timeline.

2.5.4 Continue accelerating up to speed is a self-paced task that takes place during the second half of the continuum.

2.5.5 Maintain safe lane position is a force-paced task that takes place during the second half of the continuum.

2.5.6 Check surround for unsafe situations is a self-paced task that takes place during the second half of the continuum.

Return to Table 29

Figure 20. Line Graph. Scenario 2–Left Turn on Yellow Light total estimated workload ratings for all tasks in each scenario segment.

This graph shows the overall level of workload associated with a segment. X axis itemizes task segments: approach, deceleration, decision to proceed, intersection entry, and execute turn. Y axis equals estimated workload ratings from 0 to 35. One line (solid) describes workload peaks for perceptual subtasks, a second line (solid, then broken) describes workload peaks for cognitive subtasks, and a third line (dotted) describes workload peaks for psychomotor subtasks. Intervals containing nonroutine forced-paced tasks are shaded in orange. The peak in the workload rating is high during the decision to proceed and the intersection entry for both the perceptual and cognitive subtasks.

Return to Figure 20

Figure 21. Line Graph. Scenario 2–Left Turn on Yellow Light average estimated workload ratings per task for each scenario segment.

This graph shows the average level of workload associated with a segment. X axis itemizes task segments: approach, deceleration, decision to proceed, intersection entry, and execute turn. Y axis equals estimated workload ratings from 0 to 35. One line (solid) describes workload peaks for perceptual subtasks, a second line (solid, then broken) describes workload peaks for cognitive subtasks, and a third line (dotted) describes workload peaks for psychomotor subtasks. Intervals containing nonroutine forced-paced tasks are shaded in orange. The workload rating stays within the 3 to 5 rating area for perceptual and cognitive subtasks, thought having spikes during the approach. This graph generally represents the overall level of "difficulty" associated with the tasks in a segment.

Return to Figure 21

Figure 22. Scenario Diagram. Scenario 3–Straight on Yellow Light diagram, details, and assumptions.

Diagram of intersection with the following driving segments shown: approach, decision to proceed, and intersection entry. A vehicle approaches the intersection. The speed remains at approximately 50 kilometers per hour for all segments.

Return to Figure 22

Figure 23. Line Graph. Scenario 3–Straight on Yellow Light timeline depicting duration of key segment phases and event/task milestones.

X axis equals time with task segments and task milestones marked along the axis. Y axis equals speed in kilometers per hour. Line describes speed during driving segments and at event/task milestones. The line on this graph is straight, showing only a slight decline in speed as the vehicle enters the approach segment.

Return to Figure 23

Figure 24. Scenario Diagram. Scenario 3–Straight on Yellow Light Approach segment diagram.

Diagram of intersection highlighting the approach segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. These include the lead vehicle, crosswalk directly in front of the vehicle, the stop line, traffic light, and pedestrian lights.

Return to Figure 24

Table 35.

Scenario 3–Straight on Yellow Light Approach segment relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

3.1.1 Maintain safe lane position is a forced-paced task that lasts from start to end.

3.1.2 Check surround for unsafe situations is a self-paced task that lasts from start to end.

3.1.3 Maintain safe distance from lead vehicle traveling at constant speed is a self-paced task that lasts from start to end.

3.1.4 Decelerate is a self-paced task that lasts during the first quarter of the continuum.

3.1.5 Identify intersection characteristics is a self-paced task that takes place during the second quarter of the continuum, half way through the timeline.

3.1.6 Observe status of the light is a self-paced task that focuses in the third-quarter but takes place throughout the timeline.

3.1.7 Determine if the light is about to change is a self-paced task that takes place during the last quarter of the continuum.

Return to Table 35

Figure 25. Scenario Diagram. Scenario 3–Straight on Yellow Light Scenario Decision to Proceed segment diagram.

Diagram of intersection highlighting the decision to proceed segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. These include both the lead and following vehicles, the crosswalk and stop line, the traffic light, and the oncoming vehicle.

Return to Figure 25

Table 37.

Scenario 3–Straight on Yellow Light Decision to Proceed segment relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

3.2.1 Maintain safe lane position is a forced-paced task that lasts from start to end.

3.2.2 Check surround for unsafe situations is a self-paced task that lasts from start to end.

3.2.3 Maintain safe distance from lead vehicle traveling at constant speed is a self-paced task that lasts from start to end.

3.2.4 Observe status of light is a force-paced task that lasts for the first one-quarter of the timeline.

3.2.5 Determine if lead vehicle is stopping or proceeding through intersection is a forced-paced task that lasts from the second quarter of the timeline through to the end.

3.2.6 Determine if stopping will conflict with following vehicle is a forced-paced task that lasts from the second quarter of the timeline through to the end.

3.2.7 Determine if stop can be made before intersection is a forced-paced task that lasts from the second quarter of the timeline through to the end.

3.2.8 Determine if oncoming vehicles are trying to turn left across path is a forced-paced task that lasts from the second quarter of the timeline through to the end.

Return to Table 37

Figure 26. Scenario Diagram. Scenario 3–Straight on Yellow Light Intersection Entry segment diagram.

Diagram of intersection highlighting the intersection entry segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. These include the lead vehicle that now in the intersection, the crosswalk on the far side of the intersection, and the oncoming vehicle about to enter the intersection, and vehicles approaching from both the left and right.

Return to Figure 26

Table 39.

Scenario 3–Straight on Yellow Light Intersection Entry segment relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

3.3.1 Maintain safe lane position is a forced-paced task that lasts from start to end.

3.3.2 Check surround for unsafe situations is a self-paced task that lasts from start to end.

3.3.3 Maintain safe distance from lead vehicle traveling at constant speed is a self-paced task that takes place during the first half of the continuum.

3.3.4 Check for red-light- running cross traffic is a force-paced task that lasts for the first quarter of the timeline.

3.3.5 Check for oncoming vehicles trying to turn left across path at last minute is a force-paced task that takes placed during the second quarter of the continuum.

3.3.6 Accelerate to get through the intersection is a force-paced task that takes place during the last half of the timeline.

Return to Table 39

Figure 27. Line Graph. Scenario 3–Straight on Yellow Light total estimated workload ratings for all tasks in each scenario segment.

This graph shows the overall level of workload associated with a segment. X axis itemizes task segments: approach, decision to proceed, and intersection entry. Y axis equals estimated workload ratings from 0 to 35. One line (solid) describes workload peaks for perceptual subtasks, a second line (solid, then broken) describes workload peaks for cognitive subtasks, and a third line (dotted) describes workload peaks for psychomotor subtasks. Intervals containing nonroutine forced-paced tasks are shaded in orange. The workload rating is peaks at 30 during the decision to proceed segment for both the perceptual and cognitive subtasks.

Return to Figure 27

Figure 28. Line Graph. Scenario 3–Straight on Yellow Light average estimated workload ratings per task for each scenario segment.

X axis itemizes task segments: approach, decision to proceed, and intersection entry. Y axis equals estimated workload ratings from 0 to 35. One line (solid) describes workload peaks for perceptual subtasks, a second line (solid, then broken) describes workload peaks for cognitive subtasks, and a third line (dotted) describes workload peaks for psychomotor subtasks. Intervals containing nonroutine forced-paced tasks are shaded in orange. This graph generally represents the overall level of "difficulty" associated with the tasks in a segment. The line for perceptual and cognitive subtasks follow similar paths. There are two peaks during the approach with the lowest point approximately 3.8 and the highest to just below 5. During the decision to proceed segment the lines stay near 4 and leave the graph slightly less than 4.

Return to Figure 28

Figure 29. Scenario Diagram. Scenario 4–Straight on Green Light diagram, details, and assumptions.

Diagram of intersection with the following driving segments shown: approach, prepare for lane change, execute lane change, and intersection entry. A vehicle approaches the intersection in left lane, changes to right lane behind another car waiting to turn left. The speed for all segments is approximately 50 kilometers per hour.

Return to Figure 29

Figure 30. Line Graph. Scenario 4–Straight on Green Light timeline of key segment phases duration and event/task milestones.

X axis equals time with task segments and task milestones marked along the axis. Y axis equals speed in kilometers per hour. Line describes speed during driving segments and at event/task milestones. The line is primarily level with the speed dropping only slightly in the early stage of the approach and being maintained at 50 kilometers per hour through all the remaining stages.

Return to Figure 30

Figure 31. Scenario Diagram. Scenario 4–Straight on Green Light Approach segment diagram.

Diagram of intersection highlighting the approach segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. These include the lead vehicle that is in the same lane, and all elements of the approaching intersection–crosswalk, stop line, traffic light, and pedestrian lights.

Return to Figure 31

Table 45.

Relative timing and duration of segment tasks and summary of key findings for the Approach segment of Scenario 4–Straight on Green Light. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

4.1.1 Maintain safe lane position is a forced-paced task that takes place from start to end.

4.1.2 Check surround for unsafe situations is a self-paced task that takes place from start to end.

4.1.3 Decelerate is a self-paced task that takes place in the first one-fifth of the continuum.

4.1.4 Identify intersection characteristics is a self-paced task that takes place in the second-fifth of the continuum.

4.1.5 Observe status of light is a self-paced task that takes place in the third-fifth of the continuum, in the middle of the timeline.

4.1.6 Determine if the light is about to change is a self-paced task that takes place in the fourth fifth of the continuum.

4.1.7 Observe that lead vehicle is signaling a left turn is a force-paced task that takes place at the end.

Return to Table 45

Figure 32. Scenario Diagram. Scenario 4–Straight on Green Light Prepare for Lane Change segment diagram.

Diagram of intersection highlighting the prepare for lane change segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. These include the following car in the right lane, the right lane immediately beside the vehicle, the lead car in the right lane, and the distance to the intersection.

Return to Figure 32

Table 47.

Scenario 4–Straight on Green Light Prepare for Lane Change segment relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

4.2.1 Maintain safe lane position is a force-paced task that takes place from start to end.

4.2.2 Check surround for unsafe situations is a self-pace task that takes place from start to end.

4.2.3 Decide whether lane change is legally permissible is a force-paced task that takes place throughout the first half of the continuum.

4.2.4 Determine whether there is a sufficient gap in right lane is a force-paced task that is the middle of the continuum.

4.2.5 Check rearview mirror for rear-approach traffic is a force-paced task that takes place during the last half of the continuum.

4.2.6 Check blind-spot for rear approaching traffic in right lane is a force-paced task that takes place in the last quarter of the continuum.

Return to Table 47

Figure 33. Scenario Diagram. Scenario 4–Straight on Green Light Execute Lane Change segment of scenario diagram.

Diagram of intersection highlighting the execute lane change segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. These include the following car in the right lane, the lead car in the right lane, and the distance to the center of the intersection.

Return to Figure 33

Table 49.

Scenario 4–Straight on Green Light Execute Lane Change segment of relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

4.3.1 Check surround for unsafe situations is a self-paced task that takes place from start to end.

4.3.2 Activate turn signal is a force-paced task that takes place in the first quarter of the continuum is a self-pace task that that takes place from start to end.

4.3.3 Adjust vehicle speed to avoid conflicts with right-lane lead vehicle is a forced-paced task that takes place from start to end.

4.3.4 Adjust vehicle speed to avoid conflicts with right-lane following vehicle is a forced-paced task that takes place from start to end.

4.3.5 Change lane is a forced-paced task that takes place during the last half of the continuum.

Return to Table 49

Figure 34. Scenario Diagram. Scenario 4–Straight on Green Light Intersection Entry segment diagram.

Diagram of intersection highlighting the intersection entry segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. The subject vehicle is now in the right lane along with the lead and following vehicles.

Return to Figure 34

Table 51.

Scenario 4–Straight on Green Light Intersection Entry segment of relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

4.4.1 Maintain safe lane position is a forced-paced task that takes place from start to end.

4.4.2 Check surround for unsafe situations is a self-paced task that takes place from start to end.

4.4.3 Maintain safe distance from lead vehicle traveling at constant speed is a self-paced task that takes place from start to end.

4.4.4 Check that there will be no conflict with following vehicle is a self-paced task that takes place during the first quarter of the continuum.

4.4.5 Check for red-light running cross traffic is a forced-paced task that takes place in the second quarter of the continuum.

4.4.6 Check for oncoming vehicle trying to turn left across path is a forced-paced task that takes place in the third-quarter of the continuum.

Return to Table 51

Figure 35. Line Graph. Scenario 4–Straight on Green Light total estimated workload ratings for all tasks in each scenario segment.

This graph shows the overall level of workload associated with a segment. X axis itemizes task segments: approach, prepare for lane change, execute lane change, and intersection entry. Y axis equals estimated workload ratings from 0 to 35. One line (solid) describes workload peaks for perceptual subtasks, a second line (solid, then broken) describes workload peaks for cognitive subtasks, and a third line (dotted) describes workload peaks for psychomotor subtasks. Intervals containing nonroutine forced-paced tasks are shaded in orange. The perceptual and cognitive lines follow the similar paths in the beginning. Workload rating starts at approximately 12, dips to 10, and then peaks for perceptual subtasks at 18 in the prepare for lane change segment. Toward the end that segment, the perceptual subtask workload rating lowers to 12 while the cognitive subtasks increased to 17. This drops in the intersection entry phase along with the perceptual subtasks.

Return to Figure 35

Figure 36. Line Graph. Scenario 4–Straight on Green Light average estimated workload ratings per task for each scenario segment.

X axis itemizes task segments: approach, prepare for lane change, execute lane change, and intersection entry. Y axis equals estimated workload ratings from 0 to 35. One line (solid) describes workload peaks for perceptual subtasks, a second line (solid, then broken) describes workload peaks for cognitive subtasks, and a third line (dotted) describes workload peaks for psychomotor subtasks. Intervals containing nonroutine forced-paced tasks are shaded in orange. This graph generally represents the overall level of "difficulty" associated with the tasks in a segment. The lines for both perceptual and cognitive have many changes. Workload rating for perceptual subtasks peak at 4.5 in approach, 5 in prepare for lane change, 4.5 in execute lane change, and then leaves the graph at 3.8. The line for cognitive subtasks starts at 3.5 but drops to 2 at the beginning of the preparation for lane change. It increases to 3.5 in the middle of that segment, peaks at 5.5 in the execute lane change segment, then drops, leaving the graph at 2.8.

Return to Figure 36

Figure 37. Scenario Diagram. Scenario 5–Right Turn on Green Light diagram, details, and assumptions.

Diagram of intersection with the following driving segments shown: approach, deceleration, intersection entry, and execute turn. A vehicle approaches the intersection from the right lane, continues driving in the right lane, and then executes a right turn. Speeds in each of the segments are as follows: approach, approximately 50 kilometers per hour; deceleration, 50 to 25 kilometers per hour; intersection entry 25 to 16 kilometers per hour; and execute turn, 16 to 50 kilometers per hour.

Return to Figure 37

Figure 38. Line Graph. Scenario 5–Right Turn on Green Light timeline of key segment phases duration and task milestones.

X axis equals time with task segments and task milestones marked along the axis. Y axis equals speed in kilometers per hour. Line describes speed during driving segments and at event/task milestones. The line starts at 50 kilometers per hour and drops quickly through the deceleration stage where it levels briefly at 16 kilometers per hour during intersection entry. The line then rises steadily through execution of the turn to 50 kilometers per hour.

Return to Figure 38

Figure 39. Scenario Diagram. Scenario 5–Right Turn on Green Light Approach segment diagram.

Diagram of intersection highlighting the approach segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. This includes the open lanes in front of the vehicle and all intersection characteristics including the crosswalk, pedestrian light, and traffic light.

Return to Figure 39

Table 57.

Scenario 5–Right Turn on Green Light Approach segment relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

5.1.1 Maintain safe lane position is a forced-paced task that takes place from start to end.

5.1.2 Check surround for unsafe situations is a self-paced task that takes place from start to end.

5.1.3 Decelerate is a self-paced task that takes place in the first moments of the continuum.

5.1.4 Identify intersection characteristics is a self-paced task that takes place in the second fifth of the continuum.

5.1.5 Observe status of light is a self-paced task that takes place primarily in the second fifth of the continuum, but may also start at the beginning and continue through the first half.

5.1.6 Determine if the light is about to change is a self-paced task that takes place in the middle of the continuum.

5.1.7 Identify intersection as correct turn intersection is a forced-paced task that takes place near the end of the continuum.

5.1.8 Activate turn signal is a forced-paced task at the end.

Return to Table 57

Figure 40. Scenario Diagram. Scenario 5–Right Turn on Green Light Deceleration segment diagram.

The equation reads: m subscript i,y is equal to the product of C superscript one subscript i,y and m subscript i,1 which is equal to the product of the quotient of the expected value of m subscript i,y over the expected value of m subscript i,1 and m subscript i,1.

Return to Figure 40

Table 59.

Scenario 5–Right Turn on Green Light Deceleration segment relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

5.2.1 Maintain safe lane position is a forced-paced task that takes place from start to end.

5.2.2 Check surround for unsafe situations is a self-paced task that takes place from start to the end.

5.2.3 Begin deceleration is a forced-paced task that takes place in the first quarter of the continuum.

5.2.4 Observe vehicle deceleration trajectory is a self-paced task that takes place in the after deceleration is begun and continues throughout the timeframe.

5.2.5 Maintain safe distance from decelerating following vehicles is a self-paced task that takes place in the after deceleration is begun and continues throughout the timeframe.

5.2.6 Observe status of light is a self-paced task that is concentrated near the end but may start in the middle and continue through to the end.

Return to Table 59

Figure 41. Scenario Diagram. Scenario 5–Right Turn on Green Light Intersection Entry segment diagram.

Diagram of intersection highlighting the intersection entry segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. This includes the following vehicle, the crosswalk immediately in front of the car, the left-turning vehicle in the intersection, the vehicle approaching from the left, and the traffic light.

Return to Figure 41

Table 61.

Scenario 5–Right Turn on Green Light Intersection Entry segment of relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

5.3.1 Maintain safe lane position is a forced-paced task that takes place from start to end.

5.3.2 Check surround for unsafe situations is a self-paced task that takes place from start to end.

5.3.3 Decelerate to turning speed is a self-paced task that takes place from start to end.

5.3.4 Check for conflicts with following vehicle is a self-paced task that takes place from start to end.

5.3.5 Observe status of light is a self-paced task that takes just at the start.

5.3.6 Check for red-light- running cross traffic is a forced-paced task that takes place immediately after the status of the light is observed.

5.3.7 Check for conflicts with left-turning vehicles is a forced-paced task that takes place immediately after the check of red-light-running cross traffic.

5.3.8 Check for hazards in turn path is a forced-pace task at the end of the continuum.

Return to Table 61

Figure 42. Scenario Diagram. Scenario 5–Right Turn on Green Light Execute Turn segment diagram.

Diagram of intersection highlighting the execute turn segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. This includes the area around the car itself and the left-turning vehicle, now entering the same roadway but in the left lane.

Return to Figure 42

Table 63.

Scenario 5–Right Turn on Green Light Execute Turn segment relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

5.4.1 Accelerate to initiate turn is a forced-paced task during the first half of the continuum.

5.4.2 Steer into turn is a forced-paced task during the first half of the continuum.

5.4.3 Check for hazards in turn path is a forced-paced task during the first half of the continuum.

5.4.4 Check for conflicts with left-turning vehicle is a self-paced task that takes place during the first three-quarters of the timeframe.

5.4.5 Continue accelerating up to speed is a forced-paced task that takes place during the last half of the continuum.

5.4.6 Maintain safe lane position is a forced-paced task that takes place during the last half of the continuum.

5.4.7 Check surround for unsafe situations is a self-paced task that takes place during the last half of the continuum.

Return to Table 63

Figure 43. Line Graph. Scenario 5–Right Turn on Green Light total estimated workload ratings for all tasks in each scenario segment.

This graph shows the overall level of workload associated with a segment. X axis itemizes task segments: approach, deceleration, intersection entry, and execute turn. Y axis equals estimated workload ratings from 0 to 35. One line (solid) describes workload peaks for perceptual subtasks, a second line (solid, then broken) describes workload peaks for cognitive subtasks, and a third line (dotted) describes workload peaks for psychomotor subtasks. Intervals containing nonroutine forced-paced tasks are shaded in orange. The workload for perceptual and cognitive tasks steadily rise from about 11 in approach to approximately 23 during intersection entry. The lines then drops quickly and leave the graph between 5 and 10.

Return to Figure 43

Figure 44. Line Graph. Scenario 5–Right Turn on Green Light average estimated workload ratings per task for each scenario segment.

X axis itemizes task segments: approach, deceleration, intersection entry, and execute turn. Y axis equals estimated workload ratings from 0 to 35. One line (solid) describes workload peaks for perceptual subtasks, a second line (solid, then broken) describes workload peaks for cognitive subtasks, and a third line (dotted) describes workload peaks for psychomotor subtasks. Intervals containing nonroutine forced-paced tasks are shaded in orange. This graph generally represents the overall level of "difficulty" associated with the tasks in a segment. The perceptual line rises quickly from 4 to 5 in the middle of the approach segment, the drops and remains between 3.5 and 4.5 through the remainder of the task. The cognitive subtasks are lower during the approach and level to between 3.5 and 4.5 until the execute turn segment where it increases quickly to 5. It drops halfway through that segment to 2 where it leaves the graph.

Return to Figure 44

Figure 45. Scenario Diagram. Scenario 6–Right Turn on Red Light scenario diagram, details, and assumptions.

Diagram of intersection with the following driving segments shown: approach, prepare for lane change, execute lane change, stop, prepare for turn/intersection entry, and execute turn. A vehicle approaches the intersection in left lane, changes to right lane, and executes a right turn. Speeds during each the segment are: approach, prepare for lane change, and execute lane change are maintained at approximately 50 kilometers per hour; stop is from 50 to 0 kilometers per hour, prepare for turn is 0 kilometers per hour, and execute turn is from 0 to 50 kilometers per hour.

Return to Figure 45

Figure 46. Line Graph. Scenario 6–Right Turn on Red Light Scenario timeline depicting key segment phases duration and event/task milestones.

X axis equals time with task segments and task milestones marked along the axis. Y axis equals speed in kilometers per hour. Line describes speed during driving segments and at event/task milestones. The line on the graph remains at 50 kilometers per hour up through the early phase of deceleration where it quickly drops to 0 and stays there until acceleration through execution of the turn where it leaves the graph at 25 kilometers per hour.

Return to Figure 46

Figure 47. Scenario Diagram. Scenario 6–Right Turn on Red Light Approach segment scenario diagram.

Diagram of intersection highlighting the approach segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. This includes the roadway in front of the vehicle and all elements of the intersection including the crosswalk, pedestrian lights, and traffic light.

Return to Figure 47

Table 69.

Scenario 6–Right Turn on Red Light Approach segment relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

6.1.1 Maintain safe lane position is a forced-paced task that takes place from start to end.

6.1.2 Check surround for unsafe situations is a self-paced task that takes place from start to end.

6.1.3 Decelerate is a self-paced task that takes place at the start.

6.1.4 Identify intersection as correct turn intersection is a self-paced task that takes place immediately after deceleration.

6.1.5 Identify intersection characteristics is a self-paced task that takes place immediately following identifying the intersection as the correct one.

6.1.6 Observe status of light is a self-paced task focused in the same time period as identifying intersection characteristics, but can take place from start to finish.

Return to Table 69

Figure 48. Scenario Diagram. Scenario 6–Right Turn on Red Light Prepare for Lane Change segment of scenario diagram.

Diagram of intersection highlighting the prepare for lane change segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. This includes the roadway in front of the vehicle, the areas to the vehicle's immediate right and the following vehicle in the right lane.

Return to Figure 48

Table 71.

Scenario 6–Right Turn on Red Light Prepare for Lane Change segment of relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

6.2.1 Maintain safe lane position is a forced-paced task that takes place from start to end.

6.2.2 Check surround for unsafe situations is a self-paced task that takes place from start to end.

6.2.3 Decide whether lane change is legally permissible is a forced-paced task that takes place during the first half of the continuum.

6.2.4 Confirm that there is no lead vehicle in right lane is a forced-paced task that takes place during the middle third of the continuum.

6.2.5 Check rearview mirror for rear-approaching traffic is a forced-paced task that takes place during the last half of the continuum.

6.2.6 Check blind spot for rear-approaching traffic in right lane is a forced-paced task that takes place at the end.

Return to Table 71

Figure 49. Scenario Diagram. Scenario 6–Right Turn on Red Light Execute Lane Change segment diagram.

Diagram of intersection highlighting execute lane change segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. This includes the roadway in front of the vehicle into the center of the intersection and the following vehicle in the right lane.

Return to Figure 49

Table 73.

Scenario 6–Right Turn on Red Light Execute Lane Change segment of relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

6.3.1 Check surround for unsafe situations is a self-paced task that takes place from start to end.

6.3.2 Activate turn signal is a forced-paced task that takes place during the first third of the continuum.

6.3.3 Adjust vehicle speed to avoid conflicts with right-lane following vehicle traveling at constant speed is a forced-paced task that takes place from start to end.

6.3.4 Change lane is a forced-paced task that takes during the last two-thirds of the continuum.

Return to Table 73

Figure 50. Scenario Diagram. Scenario 6–Right Turn on Red Light Stop segment diagram.

Diagram of intersection highlighting deceleration segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. The vehicle is now in the right lane and checking the following vehicle, the crosswalk, the stop line, and the traffic light.

Return to Figure 50

Table 75.

Scenario 6–Right Turn on Red Light Stop segment of relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

6.4.1 Maintain safe lane position is a forced-paced task that takes place from start to end.

6.4.2 Check surround for unsafe situations is a self-paced task that takes place from start to end.

6.4.3 Maintain safe distance from decelerating following vehicle is a self-paced task that takes place from start to end.

6.4.4 Activate turn signal is a forced-paced task that takes place at the start.

6.4.5 Begin deceleration is a forced-paced task that takes place at the start.

6.4.6 Observe vehicle stopping trajectory is a self-paced task that takes place in the middle third of the continuum.

6.4.7 Observe status of light is a self-paced task that is focused three quarters of the way through the task, but may take place from start to end.

6.4.8 Stop is a forced-paced task at the end.

Return to Table 75

Figure 51. Scenario Diagram. Scenario 6–Right Turn on Red Light Prepare for Turn/Intersection Entry segment of scenario diagram.

Diagram of intersection highlighting the prepare for turn/intersection entry segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. This includes the crosswalk that the car is in, the crosswalk in the lanes to the right, the vehicles approaching from the left, the following vehicle, and the traffic light.

Return to Figure 51

Table 77.

Scenario 6–Right Turn on Red Light Prepare for Turn/Intersection Entry segment relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

6.5.1 Check for conflicts with following vehicle is a self-paced task that takes place from start to end.

6.5.2 Make sure pedestrians/cyclists are not crossing or about to cross is a self-paced task that takes place at the start.

6.5.3 Observe status of light is a self-paced task that takes place after making sure there are no pedestrians/cyclists crossing.

6.5.4 Advance into the crosswalk is a self-paced task that takes place in the middle of the continuum.

6.5.5 Look for gap in right-going traffic is a forced-paced task that takes place during the last half of the continuum.

6.5.6 Check for vehicles in inside lane changing to outside (conflicting) lane is a forced-paced task that takes place during the last half of the continuum.

6.5.7 Check for hazards in turn path is a forced-paced task that takes place during the last half of the continuum.

Return to Table 77

Figure 52. Scenario Diagram. Scenario 6–Right Turn on Red Light Execute Turn segment diagram.

Diagram of intersection highlighting the execute turn segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. This includes the area around the turning vehicle and the cars that are coming into the intersection and will become following vehicles once the turn is complete.

Return to Figure 52

Table 79.

Scenario 6–Right Turn on Red Light Execute Turn segment of relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

6.6.1 Accelerate to initiate turn and get up to speed is a forced-paced task that takes place during the first half of the continuum.

6.6.2 Steer into turn is a forced-paced task that takes place during the first half of the continuum.

6.6.3 Check for hazards in turn path is a forced-paced task that takes place during the first half of the continuum.

6.6.4 Check for conflicts with vehicle in inside lane is a self-paced task that takes place from start and continues three-quarters of the way through the task.

6.6.5 Continue accelerating up to speed is a forced-paced task that takes place during the last half of the continuum.

6.6.6 Maintain safe lane position is a forced-paced task that takes place during the last half of the continuum.

6.6.7 Check surround for unsafe situations is a self-paced task that takes place during the last half of the continuum.

6.6.8 Maintain safe distance from following vehicle at constant speed is a self-paced task that takes place during the last half of the continuum.

Return to Table 79

Figure 53. Line Graph. Scenario 6–Right Turn on Red Light total estimated workload ratings for all tasks in each scenario segment.

This graph shows the overall level of workload associated with a segment. X axis itemizes task segments: approach, prepare for lane change, execute lane change, stop, prepare for turn/intersection entry, and execute turn. Y axis equals estimated workload ratings from 0 to 35. One line (solid) describes workload peaks for perceptual subtasks, a second line (solid, then broken) describes workload peaks for cognitive subtasks, and a third line (dotted) describes workload peaks for psychomotor subtasks. Intervals containing nonroutine forced-paced tasks are shaded in orange. The lines for this scenario have several peaks and valley as the workload rating goes up and down several times. The perceptual subtask peaks at 15 in the approach, 17 in the prepare for lane change segment, 19 in the stop segment, and 20 at the end of the prepare for turn/intersection entry segment. Each of these peaks are proceeded by a down turn, with the lowest point being 4 just prior to the steep ascent to 20 in the prepare for turn/intersection entry segment. The cognitive line follows a similar path but remains at 11 through the prepare for lane change and execute lane change segments.

Return to Figure 53

Figure 54. Line Graph. Scenario 6–Right Turn on Red Light average estimated workload ratings per task for each scenario segment.

X axis itemizes task segments: approach, prepare for lane change, execute lane change, stop, prepare for turn/intersection entry, and execute turn. Y axis equals estimated workload ratings from 0 to 35. One line (solid) describes workload peaks for perceptual subtasks, a second line (solid, then broken) describes workload peaks for cognitive subtasks, and a third line (dotted) describes workload peaks for psychomotor subtasks. Intervals containing nonroutine forced-paced tasks are shaded in orange. This graph generally represents the overall level of "difficulty" associated with the tasks in a segment. In this case, the perceptual and cognitive lines are very different. The perceptual line peaks at 5 at the beginning of the preparation of the lane change, drops to 3 through that segment, then rises to 3.8 where it stays into the stop segment. During the stop segment the line drops slightly, increases again to 3, then drops quickly to 2.5 in the middle of the prepare for turn/intersection entry. It then rises steeply to 5.2 and declines as the turn is executed. The cognitive line drops to 2.5 during the approach and reaches 3 during the preparation for the lane change. It rises steeply to 4.2, above the perceptual line, then drops to 3 at the beginning of the stop segment. It rises slightly, then drops again to just below 3 at the end of the stop segment. It begins a steady ascent through the prepare for turn/intersection entry segment where it peaks at 5.2, the same as the perceptual line, then descends as the turn is executed.

Return to Figure 54

Figure 55. Scenario Diagram. Scenario 7–Stop on Red Light diagram, details, and assumptions.

Diagram of intersection with the following driving segments shown: approach, stop, proceed through intersection. A vehicle approaches the intersection in left lane and stops at the red light. The speeds associated with each segment are: approach, approximately 50 kilometers per hour; stop, 50 to 0 kilometers per hour, and proceed through intersection at 0 to 50 kilometers per hour.

Return to Figure 55

Figure 56. Line Graph. Scenario 7–Stop on Red Light Scenario timeline depicting key segment phases duration and event/task milestones.

X axis equals time with task segments and task milestones marked along the axis. Y axis equals speed in kilometers per hour. Line describes speed during driving segments and at event/task milestones. The line is level at 50 kilometers per hour then descends quickly in the stop phase to 0. It remains at 0 until the vehicle proceeds through the intersection when it rises to 32 kilometers per hour before leaving the graph.

Return to Figure 56

Figure 57. Scenario Diagram. Scenario 7–Stop on Red Light Approach segment diagram.

Diagram of intersection highlighting the approach segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. This includes the lead vehicle and characteristic of the intersection including the crosswalk and traffic light.

Return to Figure 57

Table 85.

Scenario 7–Stop on Red Light Approach segment of relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

7.1.1 Maintain safe lane position is a forced-paced task that takes place from start to end.

7.1.2 Check surround for unsafe situations is a self-paced task that takes place from start to end.

7.1.3 Maintain safe distance from lead vehicles traveling at constant speed is a self-paced task that takes place from start to end.

7.1.4 Decelerate is a self-paced task that takes place at the start.

7.1.5 Identify intersection characteristics is a self-paced task that takes place after deceleration.

7.1.6 Observe status of light is a self-paced task that is focused three-quarters of the way through the continuum, but may take place from start to finish.

Return to Table 85

Figure 58. Scenario Diagram. Scenario 7–Stop on Red Light Stop segment diagram.

Diagram of intersection highlighting the stop segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. This includes the lead vehicle and the roadway into the middle of the intersection.

Return to Figure 58

Table 87.

Scenario 7–Stop on Red Light Stop segment of relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

7.2.1 Maintain safe lane position is a forced-paced task that takes place from start to end.

7.2.2 Check surround for unsafe situations is a self-paced task that takes place from start to end.

7.2.3 Begin deceleration is a forced-pace task at the start.

7.2.4 Observe vehicle stopping trajectory is a self-paced task in the middle third of the continuum.

7.2.5 Maintain safe distance from decelerating lead vehicle is a self-paced task that takes place from start to end.

7.2.6 Maintain safe distance from decelerating following vehicles is a self-paced task that takes place from start to end.

7.2.7 Observe status of light is a self-paced task that is focused three-quarters of the way through the continuum, but may take place from start to finish.

7.2.8 Stop is a forced-pace task at the end.

Return to Table 87

Figure 59. Scenario Diagram. Scenario 7–Stop on Red Light Proceed Through Intersection segment diagram.

Diagram of intersection highlighting proceed through intersection (or intersection entry) segment. Blue dotted outlines indicate general distribution of primary information in key perceptual tasks. This includes the lead vehicle, the crosswalk, cross-traffic vehicles on both the left and right, the complete intersection, and traffic light.

Return to Figure 59

Table 89.

Scenario 7–Stop on Red Light Proceed Through Intersection segment of relative timing and duration of segment tasks and summary of key findings. The bar chart shows both relative time required to complete tasks and sequential timing of tasks along a Start to End continuum:

7.3.1 Observe status of light is a self-paced task at the start.

7.3.2 Wait for lead vehicle to go is a forced-pace task that follows observation of the light.

7.3.3 Make sure pedestrians/cyclists are not crossing or about to cross is a self-paced task near the middle of the continuum.

7.3.4 Check for red-light- running cross traffic is a self-paced task just past the middle of the continuum.

7.3.5 Accelerate to get up to speed is a self-paced task that takes place in the last third of the continuum.

7.3.6 Maintain safe distance from accelerating lead vehicle is a self-paced task that takes place in the last third of the continuum.

7.3.7 Maintain safe lane position is a forced-paced task that takes place in the last third of the continuum.

7.3.8 Check surround for unsafe situations is a self-paced task that takes place in the last third of the continuum.

Return to Table 89

Figure 60. Line Graph. Scenario 7–Stop on Red Light total estimated workload ratings for all tasks in each scenario segment.

This graph shows the overall level of workload associated with a segment. X axis itemizes task segments: approach, stop, and proceed through intersection. Y axis equals estimated workload ratings from 0 to 35. One line (solid) describes workload peaks for perceptual subtasks, a second line (solid, then broken) describes workload peaks for cognitive subtasks, and a third line (dotted) describes workload peaks for psychomotor subtasks. Intervals containing nonroutine forced-paced tasks are shaded in orange. All lines follow the same path, with perceptual and cognitive nearly identical. The lines decrease during the approach segment then rise steadily to 20 to 22 in the middle of the stop segment. They begin steep decline to nearly 0 at the beginning of the proceed through intersection phase and rise gradually to 12 where they leave the graph. The psychomotor line is the same, but lower.

Return to Figure 60

Figure 61. Line Graph. Scenario 7–Stop on Red Light average estimated workload ratings per task for each scenario segment.

X axis itemizes task segments: approach, stop, and proceed through intersection. Y axis equals estimated workload ratings from 0 to 35. One line (solid) describes workload peaks for perceptual subtasks, a second line (solid, then broken) describes workload peaks for cognitive subtasks, and a third line (dotted) describes workload peaks for psychomotor subtasks. Intervals containing nonroutine forced-paced tasks are shaded in orange. This graph generally represents the overall level of "difficulty" associated with the tasks in a segment. The perceptual line varies between 3.5 and 4.5 through to the near end of the stop segment where it drops quickly to below 1 during the proceed through intersection segment. It the rises steeply to its peak at 5 and drops again to leave the graph at 3. The cognitive line follows a similar but more smooth path, descending to 2 during the proceed through intersection segment, then rising to 3.8 and descending to leave the chart at 3.

Return to Figure 61

Figure 62. Line Graph. Scenario 1–Left Turn on Green Light timeline depicting key temporal milestones.

X axis equals time with task segments and task milestones marked along the axis. Y axis equals speed in kilometers per hour. Line describes speed during driving segments and at event/task milestones. The approach is at 50 kilometers per hour and drops off quickly to 0 during the deceleration stage. The line stays at 0 with a slight bump to indicate possible slight accelerations during intersection entry. Prepare for turn stages is at 0 kilometers per hour. The line moves upward rapidly to 38 kilometers per hour to account for acceleration during execution of the turn.

Return to Figure 62

Table 94.

Equation 1. D subscript read equals 0.48 meter times the height of text in millimeters

Equation 2. D subscript cutoff equals D subscript read minus D subscript decel

Equation 3. T subscript sign equals the D subscript cutoff divided by V subscript 0

Return to Table 94

Table 95.

Equation 4. T subscript decel equals negative V subscript 0 divided by A

Equation 5. D subscript decel equals the sum of the following: the product 0.5 times A times T subscript decel squared, end of product.To that product add the product V subscript 0 times the sum of T subscript decel plus T subscript B R T

Return to Table 95

Table 96.

Equation 6. T subscript stop equals T subscript B R T plus T subscript decel

Return to Table 96

Table 97.

Equation 7. T subscript turn equals the sum of the following: the square root of the product 2 times D subscript turn, end of product, that product divided by A, end of square root. To that square root add T subscript A R T

Return to Table 97

Figure 63. Line Graph. Scenario 2–Left Turn on Yellow Light timeline depicting key temporal milestones.

X axis equals time with task segments and task milestones marked along the axis. Y axis equals speed in kilometers per hour. Line describes speed during driving segments and at event/task milestones. The graph shows the change in speed during the approach through execution of the turn. It starts at 50 kilometers per hour, drops quickly to 16 kilometers per hour during intersection entry and then rises to 50 kilometers per hour through execution of the turn.

Return to Figure 63

Table 99.

Equation 8. T subscript decel equals negative V subscript 0 divided by A

Equation 9. D subscript decel equals the sum of the following: the product of 0.5 times A times T subscript decel squared, end of product, To that product add product V subscript 0 times T subscript decel, end of product

Return to Table 99

Table 101.

Equation 10. T subscript TV equals the following quotient: the sum of V subscript F minus V subscript 0, end of sum, that sum divided by A

Equation 11. D subscript TV equals the sum of the following: the product of 0.5 times A times T subscript TV squared, end of product, plus the product V subscript 0 times T subscript TV

Return to Table 101

Table 102.

Equation 12. T subscript stopline equals the quotient of the following: the sum of D subscript decel minus D subscript TV, end of sum, that sum divided by V

Equation 13. T subscript TP equals the quotient of D subscript TP divided by V

Return to Table 102

Table 103.

Equation 14. D subscript A R T equals V subscript 0 times T subscript A R T

Equation 15. D subscript turn equals D subscript path minus D subscript A R T

Equation 16. T subscript turn equals negative V subscript 0 plus the square root of V subscript 0 squared plus 2 times A times D subscript turn, end of square root, all divided by A

Return to Table 103

Table 104.

Equation 17. T subscript decel equals negative V subscript 0 divided by A

Equation 18. T subscript stop equals T subscript E R T plus T subscript decel

Return to Table 104

Table 105.

Equation 19. T subscript hazard equals T subscript E R T plus T subscript response

Return to Table 105

Figure 64. Line Graph. Scenario 3–Straight on Yellow Light timeline depicting key temporal milestones.

X axis equals time with task segments and task milestones marked along the axis. Y axis equals speed in kilometers per hour. Line describes speed during driving segments and at event/task milestones. The line on this graph is straight, showing only a slight decline in speed as the vehicle enters the approach segment.

Return to Figure 64

Table 107.

Equation 20. D subscript yellow equals V subscript 0 times T subscript yellow

Equation 21. D subscript proceed equals D subscript yellow minus D subscript i n t

Equation 22. T subscript task equals the sum of the following: the quotient of the sum D subscript proceed minus D subscript stop, end sum, and that sum divided by V subscript 0. From that quotient subtract T subscript D R T

Return to Table 107

Table 108.

Equation 23. D subscript R T equals V subscript 0 time T subscript B R T

Equation 24. T subscript B R equals negative V subscript 0 divided by A

Equation 25. D subscript B R equals the sum of the following: the product 0.5 times A times T subscript B R squared, end of product. To that product add the product V subscript 0 time T subscript B R

Equation 26. T subscript stop equals T subscript BRT plus T subscript BR

Equation 27. D subscript stop equals D subscript B R T plus d subscript B R

Equation 28. T subscript i n t equals D subscript i n t divided by V subscript 0

Return to Table 108

Table 109.

Equation 29. T subscript hazard equals T subscript E R T plus T subscript response

Return to Table 109

Table 110.

Equation 30. T subscript hazard equals T subscript E R T plus T subscript response

Return to Table 110

Figure 65. Line Graph. Scenario 4–Straight on Green Light timeline depicting key temporal milestones.

X axis equals time with task segments and task milestones marked along the axis. Y axis equals speed in kilometers per hour. Line describes speed during driving segments and at event/task milestones. The line is primarily level with the speed dropping only slightly in the early stage of the approach and being maintained at 50 kilometers per hour through all the remaining stages.

Return to Figure 65

Table 112.

Equation 31. T subscript decel capital L equals negative V subscript 0 divided by A

Equation 32. D subscript decel capital L equals negative V subscript 0 squared divided by the product 2 times A

Return to Table 112

Table 114.

Equation 33. T subscript stopline equals T subscript T T C minus the quotient 5.8 divided by V subscript 0

Return to Table 114

Table 115.

Equation 34. T subscript hazard equals T subscript E R T plus T subscript response

Return to Table 115

Table 116.

Equation 35. T subscript hazard equals T subscript E R T plus T subscript response

Return to Table 116

Figure 66. Line Graph. Scenario 5–Right Turn on Green Light timeline depicting key temporal milestones.

X axis equals time with task segments and task milestones marked along the axis. Y axis equals speed in kilometers per hour. Line describes speed during driving segments and at event/task milestones. The line starts at 50 kilometers per hour and drops quickly through the deceleration stage where it levels briefly at 16 kilometers per hour during intersection entry. The line then rises steadily through execution of the turn to 50 kilometers per hour.

Return to Figure 83

Table 118.

Equation 36. D subscript read equals 0.48 meter times the height of text in millimeters

Equation 37. D subscript cutoff equals D subscript read minus D subscript decel

Equation 38. T subscript cutoff equals the D subscript cutoff divided by V subscript 0

Return to Table 118

Table 119.

Equation 39. T subscript decel equals negative V subscript 0 divided by A

Equation 40. D subscript decel equals the sum of the following: the product 0.5 times A times T subscript decel squared, end of product. To that product add the product V subscript 0 times T subscript decel

Return to Table 119

Table 120.

Equation 41. T subscript T V equals the quotient of the following: the sum of V subscript F minus V subscript 0, end of sum, that sum divided by A

Equation 42. D subscript T V equals the sum of the following: the product 0.5 times A times T subscript T V squared, end of product. To that product add the product V subscript 0 times T subscript T V

Return to Table 120

Table 121.

Equation 43. T subscript stopline equals the quotient of the following: the sum of D subscript decel minus D subscript TV, end of sum, that sum divided by V

Equation 44. T subscript T P equals D subscript T P divided by V

Return to Table 121

Table 122.

Equation 45. D subscript A R T equals V subscript 0 times T subscript A R T

Equation 46. D subscript turn equals D subscript path minus D subscript A R T

Equation 47. T subscript turn equals negative V subscript 0 plus the square root of V subscript 0 squared plus 2 times A times D subscript turn, end of square root, all divided by A

Return to Table 122

Table 123.

Equation 48. T subscript decel equals negative V subscript 0 divided by A

Equation 49. T subscript stop equals T subscript E R T plus T subscript decal

Return to Table 123

Figure 67. Line Graph. Scenario 6–Right Turn on Red Light timeline depicting key temporal milestones.

X axis equals time with task segments and task milestones marked along the axis. Y axis equals speed in kilometers per hour. Line describes speed during driving segments and at event/task milestones. The line on the graph remains at 50 kilometers per hour up through the early phase of deceleration where it quickly drops to 0 and stays there until acceleration through execution of the turn where it leaves the graph at 25 kilometers per hour.

Return to Figure 67

Table 127.

Equation 50. T subscript decel equals negative V subscript 0 divided by A

Return to Table 127

Table 128.

Equation 51. T subscript stop equals T subscript B R T plus T subscript decel

Return to Table 128

Table 129.

Equation 52. T subscript turn equals the sum of the following: the square root of the product 2 times D subscript turn, end of product, that product divided by A, end of square root, to that square root add T subscript A R T

Return to Table 129

Figure 68. Line Graph. Scenario 7–Stop on Red Light timeline depicting key temporal milestones.

X axis equals time with task segments and task milestones marked along the axis. Y axis equals speed in kilometers per hour. Line describes speed during driving segments and at event/task milestones. The line is level at 50 kilometers per hour then descends quickly in the stop phase to 0. It remains at 0 until the vehicle proceeds through the intersection when it rises to 32 kilometers per hour before leaving the graph.

Return to Figure 68

Table 131.

Equation 53. T subscript B R L equals negative V subscript 0 divided by A

Equation 54. T subscript delta equals V subscript 0 times T subscript G A P

Return to Table 131

Table 132.

Equation 55. T subscript decel equals negative V subscript 0 divided by A

Equation 56. T subscript stop equals T subscript B R T plus T subscript D R T plus T subscript decel

Return to Table 132

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