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Table 8.5. Categorized Critical Factors for Crashes and Near Crashes in Project 7
Critical Factor Crashes Crashes: Tire Strikes Near Crashes
Critical reason not coded to this vehicle. 1 7.1% 0 0% 29 29.6%
Driver-related factor (critical nonperformance errors), including sleep; heart attack 0 0% 0 0% 1 1.0%
or other physical impairment of the ability to act; drowsiness, fatigue, or other
reduced alertness; other critical nonperformance
Driver-related factor (recognition errors), including inattention; internal distraction; 2 14.3% 0 0% 30 30.6%
external distraction; inadequate surveillance (e.g., failure to look); other or
unknown recognition error
Driver-related factor (decision errors), including too fast or too slow; misjudgment 1 7.1% 2 14.3% 18 18.4%
of gap; following too closely or unable to respond to unexpected actions;
false assumption of other road user's actions; apparently intentional sign
or signal violation; illegal U-turn or other illegal maneuver; failure to turn on
headlamps; inadequate evasive action; aggressive driving; other or unknown
decision error
Driver-related factor (performance errors), including panic or freezing; over- 2 14.3% 3 21.4% 7 7.1%
compensation; poor directional control; other or unknown performance error
Environment-related factor, including sign missing; view obstruction by roadway 0 0% 9 64.3% 2 2.1%
design; roadway geometry; sight distance; maintenance problems; slick roads;
other highway-related conditions
Environment-related factor, including glare, blowing debris, animal or object 8 57.2% 0 0% 11 11.2%
in roadway
Total 14 100% 14 100% 98 100%
456 baseline events, each 30 s long, was selected. Data reduc- driver not seeing the other vehicle during a lane change
tionists used the data directory and coded a variety of variables or merge.
from these 456 randomly selected baseline driving events or
brief driving periods. One random baseline event was selected
Countermeasures
for each driver-week of data collection. Baseline events were
described using many of the same variables used to describe A close examination of the event causations reveals that a
safety-critical events. The goal of identifying baseline events significant portion of the crashes or near crashes happened
was to provide a comparison between normal driving and because of driver errors, such as inattention, distraction, or
driving during critical events. For example, the proportion of judgment errors. To prevent these events, the driver's response
time spent driving under various conditions and the propor- should be altered, his or her attention should be improved,
tion of time drivers performed various behaviors (e.g., eating, or his or her driving habits should be corrected. The most
drinking, talking on citizens band [CB] radio or cell phone) frequently suggested functional countermeasures relating to
were compared across different situations (1). modifying driver behavior include increasing driver recognition
Because only the subject vehicle was equipped with data of specific highway crash threats (improving driver recognition
collection units, only the behavior of the driver in that vehicle of forward threats), increasing driver attention, improving
was coded and documented. As shown in Table 8.6, the most driver situation awareness, and defensive driving. The team
frequent critical factor for crashes was an object in the roadway, examined the video data from Project 5, and the results are
followed by driver-related factors associated with recognition listed in Table 8.7. Most events are preventable by modifying
errors, decision errors, and performance errors; each con- driver behavior or increasing the attention level. The percentage
stituted 20% of the total cases. Not surprisingly, almost all indicates the portion of crashes and near crashes that would
(75%) the tire strikes involved some type of improper turn. have been avoided if the suggested countermeasures had been
The next two largest categories of contributing factor for applied. It was not unusual that more than one countermeasure
crashes: tire strikes are driver performance error and driver could be selected for an event when the contributing factor
decision error, respectively. For near crashes, the most frequent was a combination of factors. Therefore, the total may be more
factor is driver-related recognition errors; more than 40% than 100%.
of near crashes were caused by inattention or distraction. Of Because of the massive size of the data, the countermeasures
these near crashes, almost one-quarter involved the subject identification for Project 6 was not as detailed as for projects
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Table 8.6. Contributing Factors for Crashes in Project 8
Critical Factor Crashes Crashes: Tire Strikes Near Crashes
Critical reason not coded to this vehicle 0 0% 0 0% 16 26.2%
Driver-related factor (critical nonperformance errors), including sleep; heart attack 0 0% 0 0% 4 6.6%
or other physical impairment of the ability to act; drowsiness, fatigue, or other
reduced alertness; other critical nonperformance
Driver-related factor (recognition errors), including inattention; internal distraction; 1 20% 0 0% 27 44.3%
external distraction; inadequate surveillance (e.g., failure to look); other or
unknown recognition error
Driver-related factor (decision errors), including too fast or too slow; misjudgment 1 20% 1 12.5% 6 9.8%
of gap; following too closely or unable to respond to unexpected actions;
false assumption of other road user's actions; apparently intentional sign
or signal violation; illegal U-turn or other illegal maneuver; failure to turn on
headlamps; inadequate evasive action; aggressive driving; other or unknown
decision error
Driver-related factor (performance errors), including panic or freezing; over- 1 20% 1 12.5% 5 8.2%
compensation; poor directional control; other or unknown performance error
Environment-related factor, including sign missing; view obstruction by roadway 0 0% 6 75% 2 3.2%
design; roadway geometry; sight distance; maintenance problems; slick roads;
other highway-related conditions
Environment-related factor, including: glare, blowing debris, animal or object 2 40% 0 0% 1 1.6%
in roadway
Total 5 100% 8 100% 61 100%
discussed earlier. The team did differentiate avoidable crashes which consists of a single analog black-and-white camera,
from unavoidable or likely avoidable crashes and near crashes, a personal computer with a frame-grabber card, and an
as shown in Table 8.8. Almost 40% of crashes can or are likely interface-to-vehicle network for obtaining ground speed.
to be prevented. More than 80% of near crashes can or are Distance from the center of the car to left and right lane
likely to be prevented, given reasonable countermeasures. markings, the angular offset between the car centerline
The detailed countermeasures to safety-critical events in and road centerline, the approximate road curvature, and
Project 7 and Project 8 are illustrated in Tables 8.9 and 8.10 marking characteristics can be measured and calculated to
(1; 2), respectively. Because of multiple countermeasures appli- determine whether the car remains in the lane or is cross-
cable to one event, the total may be more than 100%. ing lines. A similar system was developed by UMTRI. A
Tables 8.9 and 8.10 list the functional countermeasures that lane-tracking system can be used mainly to alert a driver
describe an intervention into the driving situation. Specifically, in circumstances of decreased alertness. It can also be used
to technologically modify drivers' behaviors, warning systems to correct drivers' recognition errors, decision errors, and
can be used to alert drivers so that they are not distracted or to performance errors (13).
correct driving habits to improve safety. Many of these systems, 3. ACC System. Instead of simply maintaining a preset tar-
some of which are provided in the following list, have been get speed, as does a CCC system, an ACC system is prima-
tested in previous studies as technical countermeasures. rily a speed and headway controller. It can modulate speed
and use throttle and brakes simultaneously to manage
1. FCW System. An FCW system measures the headway headway to the leading vehicle. Usually an ACC system
between the subject vehicle and the leading vehicle. It holds a maximum braking authority. In Project 2, this
issues a visual or audio warning when the equipped vehicle value is 0.3 g. When the headway decreases to the point at
approaches the leading vehicle too rapidly. The system is which the maximum braking response is required, the
effective in correcting drivers' performance errors and system will issue an alert or apply braking. This system will
decision errors. It is even more effective in alerting an benefit drivers with recognition errors, a decreased alertness
inattentive or a less-alert driver (3). level, and some extent of decision errors and performance
2. Lane Tracking System/LDWS. A lane-tracking system or errors (3).
an LDWS usually can measure lane-keeping behavior. For 4. CSWS. A CSWS can usually help drivers slow down to a safe
example, VTTI developed a lane tracker called Road Scout, speed before entering an upcoming curve. It uses GPS and
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Table 8.7. Countermeasures by Category for Project 5
Crashes and Near Crashes
Freeway Arterial Total
No countermeasure applicable 5 6.5% 6 26.0% 11 11.0%
1. Increase driver alertness (reduce drowsiness) 2 2.6% 0 0.0% 2 2.0%
2. Prevent drift lane departures 1 1.3% 0 0.0% 1 1.0%
3. Improve vehicle control on curves 0 0.0% 0 0.0% 0 0.0%
4. Improve vehicle control on slippery road surfaces 0 0.0% 0 0.0% 0 0.0%
5. Improve vehicle control during braking 0 0.0% 0 0.0% 0 0.0%
6. Improve vehicle control during evasive steering 0 0.0% 0 0.0% 0 0.0%
7. Increase driver attention to forward scene 15 19.5% 1 4.3% 16 16.0%
8. Improve driver use of mirrors or provide better information from mirrors 0 0.0% 0 0.0% 0 0.0%
9. Improve general driver situation awareness and defensive driving 1 1.3% 0 0.0% 1 1.0%
10. Reduce travel speed 1 1.3% 0 0.0% 1 1.0%
11. Reduce speed on downgrades 0 0.0% 0 0.0% 0 0.0%
12. Reduce speed on curves or turns 0 0.0% 0 0.0% 0 0.0%
13. Reduce speed at or on exits (including ramps) 0 0.0% 0 0.0% 0 0.0%
14. Limit top speed to 70 mph (except on downgrades) 0 0.0% 0 0.0% 0 0.0%
15. Increase driver recognition of specific highway crash threats: stopped vehicle(s) in lane 14 18.2% 0 0.0% 14 14.0%
ahead, traveling in same direction
16. Increase driver recognition of specific highway crash threats: moving or decelerating 55 71.4% 17 73.9% 72 72.0%
vehicle(s) in lane ahead, traveling in same direction
17. Increase driver recognition of specific highway crash threats: vehicle in left adjacent lane 2 2.6% 0 0.0% 2 2.0%
on highway
18. Increase driver recognition of specific highway crash threats: vehicle in right adjacent lane 1 1.3% 1 4.3% 2 2.0%
on highway
19. Increase driver recognition of specific highway crash threats: vehicle in left adjacent lane 0 0.0% 0 0.0% 0 0.0%
during merging maneuver
20. Increase driver recognition of specific highway crash threats: vehicle in right adjacent lane 0 0.0% 0 0.0% 0 0.0%
during merging maneuver
21. Increase driver recognition or gap judgment recrossing or oncoming traffic at intersections 0 0.0% 0 0.0% 0 0.0%
22. Improve driver response execution of crossing or turning maneuver at intersections 0 0.0% 0 0.0% 0 0.0%
(performance failure)
23. Improve driver recognition or gap judgment response execution at intersection 0 0.0% 0 0.0% 0 0.0%
24. Improve driver compliance with intersection traffic signal controls (both intentional and 0 0.0% 0 0.0% 0 0.0%
unintentional intersection control violations)
25. Improve driver compliance with intersection traffic sign controls 0 0.0% 0 0.0% 0 0.0%
26. Increase forward headway during vehicle following 9 11.7% 2 8.7% 11 11.0%
27. Improve driver night vision in the forward field 0 0.0% 0 0.0% 0 0.0%
28. Provide warning to prevent rear encroachment or tailgating by other vehicle 0 0.0% 0 0.0% 0 0.0%
29. Provide advisory to driver regarding reduced road-tire friction (i.e., associated with 0 0.0% 0 0.0% 0 0.0%
slippery roads)
30. Prevent vehicle mechanical failure 0 0.0% 0 0.0% 0 0.0%
(continued on next page)
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Table 8.7. Countermeasures by Category for Project 5 (continued)
Crashes and Near Crashes
Freeway Arterial Total
31. Prevent splash and spray from this vehicle affecting other vehicle(s) 0 0.0% 0 0.0% 0 0.0%
32. Improve driver recognition or gap judgment relating to oncoming vehicle during 0 0.0% 0 0.0% 0 0.0%
passing maneuver
33. Prevent animals from crossing roadways 0 0.0% 0 0.0% 0 0.0%
34. Provide driver with navigation system 0 0.0% 0 0.0% 0 0.0%
35. Aid to vertical clearance estimation 0 0.0% 0 0.0% 0 0.0%
36. Prevent or reduce trailer off-tracking outside travel lane or path 0 0.0% 0 0.0% 0 0.0%
97. Provide advance warning of need to stop at traffic sign or signal 0 0.0% 0 0.0% 0 0.0%
98. Driver error or vehicle failure apparent but countermeasure unknown 0 0.0% 0 0.0% 0 0.0%
99. Unknown 0 0.0% 0 0.0% 0 0.0%
Total 101 131.2% 21 91.3% 133 133.0%
Events Total 77 100% 23 100% 100 100.00%
Table 8.8. Preventability of Crashes in Project 6
Avoidable Likely Avoidable Unavoidable
Near Near Near
Amendable Factor Crashes Crashes Crashes Crashes Crashes Crashes
Correct driver-related factor, including sleep; drowsiness 4 (5.8%) 20 (2.6%) 0 (0.0%) 1 (0.1%) 4 (5.8%) 12 (1.6%)
or other reduced alertness; other critical nonperformance
Correct driver-related factor, including inattention; internal 13 (18.8%) 109 (14.3%) 0 (0.0%) 29 (3.8%) 9 (13.0%) 63 (8.3%)
distraction; external distraction; inadequate surveillance
(e.g., failure to look); other or unknown recognition error
Correct driver-related factor, including too fast or too slow; 6 (8.7%) 134 (17.6%) 1 (1.4%) 60 (7.9%) 12 (17.4%) 24 (3.2%)
misjudgment of gap; following too closely to respond to
unexpected actions; false assumption of other road user's
actions; apparently intentional sign or signal violation;
illegal U-turn or other illegal maneuver; failure to turn on
headlamps; inadequate evasive action; aggressive driving;
other or unknown decision error
Correct driver-related factor, including poor directional 0 (0.0%) 5 (0.7%) 0 (0.0%) 20 (2.6%) 1 (1.4%) 5 (0.7%)
control; other or unknown performance error
Correct environment-related factor, including sign missing; 0 (0.0%) 12 (1.6%) 0 (0.0%) 14 (1.8%) 2 (2.9%) 0 (0.0%)
view obstruction by roadway design; roadway geometry;
sight distance; maintenance problems; slick roads;
other highway-related conditions
Correct environment-related factor, including glare, 0 (0.0%) 9 (1.2%) 0 (0.0%) 20 (2.6%) 4 (5.8%) 0 (0.0%)
blowing debris, animal or object in roadway.
Not correctable: crashes or near crashes caused by others 3 (4.3%) 33 (4.3%) 0 (0.0%) 164 (21.6%) 10 (14.5%) 27 (3.5%)
Total 26 (38%) 322 (42%) 1 (1%) 308 (40%) 42 (61%) 131 (17%)
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Table 8.9. Countermeasures by Category for Project 7
Crashes:
Crashes Tire Strikes Near Crashes
No countermeasure applicable 1 7.1% 0 0.0% 18 18.4%
1. Increase driver alertness (reduce drowsiness) 3 21.4% 0 0.0% 7 7.1%
3. Prevent drift lane departures 0 0.0% 0 0.0% 4 4.1%
4. Improve vehicle control on curves 0 0.0% 0 0.0% 0 0.0%
5. Improve vehicle control on slippery road surfaces 0 0.0% 0 0.0% 0 0.0%
6. Improve vehicle control during braking 0 0.0% 0 0.0% 0 0.0%
7. Improve vehicle control during evasive steering 0 0.0% 0 0.0% 1 1.0%
8. Increase driver attention to forward scene 3 21.4% 0 0.0% 28 28.6%
9. Improve driver use of mirrors or provide better information from mirrors 0 0.0% 0 0.0% 3 3.1%
10. Improve general driver situation awareness and defensive driving 1 7.1% 0 0.0% 9 9.2%
12. Reduce travel speed 0 0.0% 0 0.0% 3 3.1%
13. Reduce speed on downgrades 0 0.0% 0 0.0% 0 0.0%
14. Reduce speed on curves or turns 0 0.0% 0 0.0% 1 1.0%
15. Reduce speed at or on exits (including ramps) 0 0.0% 0 0.0% 1 1.0%
16. Limit top speed to 70 mph (except on downgrades) 0 0.0% 0 0.0% 0 0.0%
17. Increase driver recognition of specific highway crash threats: stopped vehicle(s) in 1 7.1% 0 0.0% 4 4.1%
lane ahead, traveling in same direction
18. Increase driver recognition of specific highway crash threats: moving or decelerating 0 0.0% 0 0.0% 6 6.1%
vehicle(s) in lane ahead, traveling in same direction
19. Increase driver recognition of specific highway crash threats: vehicle in left adjacent 0 0.0% 0 0.0% 3 3.1%
lane on highway
20. Increase driver recognition of specific highway crash threats: vehicle in right adjacent 0 0.0% 0 0.0% 1 1.0%
lane on highway
21. Increase driver recognition of specific highway crash threats: vehicle in left adjacent 0 0.0% 0 0.0% 0 0.0%
lane during merging maneuver
22. Increase driver recognition of specific highway crash threats: vehicle in right adjacent 0 0.0% 0 0.0% 0 0.0%
lane during merging maneuver
23. Increase driver recognition or gap judgment regarding crossing or oncoming traffic 0 0.0% 0 0.0% 1 1.0%
at intersections
25. Improve driver response execution of crossing or turning maneuver at intersections 2 14.3% 5 35.7% 2 2.0%
(performance failure)
26. Improve driver recognition or gap judgment response execution at intersection 0 0.0% 0 0.0% 0 0.0%
27. Improve driver compliance with intersection traffic signal controls (both intentional 0 0.0% 0 0.0% 0 0.0%
and unintentional intersection control violations)
28. Improve driver compliance with intersection traffic sign controls 0 0.0% 0 0.0% 0 0.0%
29. Increase forward headway during vehicle following 0 0.0% 0 0.0% 2 2.0%
30. Improve driver night vision in the forward field 0 0.0% 0 0.0% 5 5.1%
32. Provide warning to prevent rear encroachment or tailgating by other vehicle 0 0.0% 0 0.0% 0 0.0%
33. Provide advisory to driver regarding reduced road-tire friction (i.e., associated with 0 0.0% 0 0.0% 0 0.0%
slippery roads)
34. Prevent vehicle mechanical failure 0 0.0% 0 0.0% 0 0.0%
36. Prevent splash and spray from this vehicle affecting other vehicle(s) 0 0.0% 0 0.0% 0 0.0%
(continued on next page)
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Table 8.9. Countermeasures by Category for Project 7 (continued)
Crashes:
Crashes Tire Strikes Near Crashes
37. Improve driver recognition or gap judgment relating to oncoming vehicle during 0 0.0% 0 0.0% 0 0.0%
passing maneuver
38. Prevent animals from crossing roadways 4 28.6% 0 0.0% 9 9.2%
39. Provide driver with navigation system 2 14.3% 1 7.1% 1 1.0%
40. Aid to vertical clearance estimation 2 14.3% 0 0.0% 0 0.0%
41. Prevent or reduce trailer off-tracking outside travel lane or path 0 0.0% 7 50.0% 5 5.1%
42. Provide advance warning of need to stop at traffic sign or signal 0 0.0% 0 0.0% 3 3.1%
98. Driver error or vehicle failure apparent but countermeasure unknown 1 7.1% 2 14.3% 0 0.0%
99. Unknown 1 7.1% 0 0.0% 2 2.0%
Total 21 150.0% 15 107.1% 119 121.4%
Events Total 14 100% 14 100% 98 100%
Table 8.10. Countermeasures by Category for Project 8
Crashes: Near
Crashes Tire Strikes Crashes
No countermeasure applicable 0 0% 0 0% 11 18%
1. Increase driver alertness (reduce drowsiness) 0 0% 1 13% 7 11%
2. Prevent drift lane departures 0 0% 0 0% 18 30%
3. Improve vehicle control on curves 0 0% 0 0% 1 2%
4. Improve vehicle control on slippery road surfaces 0 0% 0 0% 1 2%
5. Improve vehicle control during braking 0 0% 0 0% 0 0%
6. Improve vehicle control during evasive steering 0 0% 0 0% 0 0%
7. Increase driver attention to forward scene 0 0% 0 0% 16 26%
8. Improve driver use of mirrors or provide better information from mirrors 2 40% 0 0% 11 18%
9. Improve general driver situation awareness and defensive driving 3 60% 2 25% 23 38%
10. Reduce travel speed 0 0% 0 0% 2 3%
11. Reduce speed on downgrades 0 0% 0 0% 0 0%
12. Reduce speed on curves or turns 0 0% 0 0% 1 2%
13. Reduce speed at or on exits (including ramps) 0 0% 0 0% 0 0%
14. Limit top speed to 70 mph (except on downgrades) 0 0% 0 0% 0 0%
15. Increase driver recognition of specific highway crash threats: stopped vehicle(s) in lane ahead, 0 0% 0 0% 0 0%
traveling in same direction
16. Increase driver recognition of specific highway crash threats: moving or decelerating vehicle(s) 0 0% 0 0% 3 5%
in lane ahead, traveling in same direction
17. Increase driver recognition of specific highway crash threats: vehicle in left adjacent lane 0 0% 0 0% 9 15%
on highway
18. Increase driver recognition of specific highway crash threats: vehicle in right adjacent lane 1 20% 0 0% 6 10%
on highway
19. Increase driver recognition of specific highway crash threats: vehicle in left adjacent lane during 0 0% 0 0% 3 5%
merging maneuver
(continued on next page)
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Table 8.10. Countermeasures by Category for Project 8 (continued)
Crashes: Near
Crashes Tire Strikes Crashes
20. Increase driver recognition of specific highway crash threats: vehicle in right adjacent lane 0 0% 0 0% 1 2%
during merging maneuver
21. Increase driver recognition or gap judgment regarding crossing or oncoming traffic 0 0% 0 0% 0 0%
at intersections
22. Improve driver response execution of crossing or turning maneuver at intersections 0 0% 1 13% 0 0%
(performance failure)
23. Improve driver recognition or gap judgment response execution at intersection 0 0% 0 0% 0 0%
24. Improve driver compliance with intersection traffic signal controls (both intentional and
unintentional intersection control violations) 0 0% 0 0% 1 2%
25. Improve driver compliance with intersection traffic sign controls 0 0% 0 0% 0 0%
26. Increase forward headway during vehicle following 0 0% 0 0% 2 3%
27. Improve driver night vision in the forward field 0 0% 0 0% 0 0%
28. Provide warning to prevent rear encroachment or tailgating by other vehicle 0 0% 0 0% 0 0%
29. Provide advisory to driver regarding reduced road-tire friction (i.e., associated with slippery roads) 0 0% 0 0% 0 0%
30. Prevent vehicle mechanical failure 0 0% 0 0% 0 0%
31. Prevent splash and spray from this vehicle affecting other vehicle(s) 0 0% 0 0% 0 0%
32. Improve driver recognition or gap judgment relating to oncoming vehicle during passing maneuver 0 0% 0 0% 0 0%
33. Prevent animals from crossing roadways 1 20% 0 0% 1 2%
34. Provide driver with navigation system 1 20% 1 13% 1 2%
35. Aid to vertical clearance estimation 0 0% 0 0% 0 0%
36. Prevent or reduce trailer off-tracking outside travel lane or path 0 0% 2 25% 0 0%
97. Provide advance warning of need to stop at traffic sign or signal 0 0% 5 63% 1 2%
98. Driver error or vehicle failure apparent but countermeasure unknown 0 0% 1 13% 0 0%
99. Unknown 0 0% 0 0% 0 0%
Total 8 160% 13 163% 119 195%
Event Total 5 100% 8 100% 61 100%
digital maps to anticipate curve locations and radiuses. time to allow safe passage through the intersection if
Combined with recent driver control actions (turning signal necessary (5).
and lateral acceleration), it determines if it is appropriate to 6. Lateral Vehicle Detection (LVD). LVD usually consists
issue a warning. The system is effective in correcting driver of lateral cameras, a lane change assistance system, and a
performance errors, recognition errors, and decision errors. lateral collision warning system. The main purpose of LVD
It also helps to alert drivers of upcoming changes in road- is to aid drivers to detect movements of vehicles in adjacent
way geometry (4). lanes and conduct corresponding maneuvers. The system
5. Dilemma Zone Mitigation (DZM). Many crashes that will issue a warning when it determines that a lateral vehi-
occur at signalized intersections are associated with dilemma cle is trying to cut in front of the subject vehicle in an
zones; for example, when faced with a yellow light, some unsafe way (6).
drivers may decide to proceed through and others may 7. Intelligent Speed Adaption System. In this system, developed
decide to stop. Components of DZM usually include a in Sweden, GPS was used to locate a car on a digital map.
carefully designed signal-timing cycle with an effective The speed limit on that roadway was retrieved from the
vehicle detection system that will identify the speed and database, and the real speed of the vehicle was compared
size of vehicles, as well as the distance to the stopping with the speed limit. The system adopts interventions that
line and provide additional safety by extending green are preprogrammed in the vehicle (7).
