Common Crash Configurations

General Description

Numerous studies have identified the defining characteristics of different crash configurations and their contributing factors (Najm, Sen, Smith, & Campbell, 2003; Sullivan & Flannagan, 2003; Sen, Najm, and Smith, 2003). By understanding typical crash situations, research can develop and assess countermeasures to reduce crash likelihood.

Rear-End Collisions
The majority of rear-end collisions occur when a lead vehicle stops or slows down while in the immediate path of another vehicle (Najm, Sen, Smith, & Campbell, 2003; Sullivan & Flannagan, 2003). Najm, Sen et al. (2003) identified the ten most common configurations, but only the top three are discussed here. The most common pre-crash scenario, accounting for 59.1% of all rear-end collisions, involves a vehicle traveling “at a constant speed on a straight road” colliding with a stopped vehicle in its path (Najm, Sen et al., 2003, p.8). The second most common situation, (26.5% of all rear-end collisions) involves two vehicles traveling at similar velocities in the same direction on a straight road. A collision-situation evolves when the deceleration rate of the lead vehicle exceeds the braking capabilities of the following vehicle. The third most prevalent situation (9.5% of all rear-end collisions) arises when a vehicle traveling at a “constant speed on a straight road encounters a lead vehicle traveling at a lower constant speed ahead” (Najm, Wiacek, & Burgett, 1998, p.6).

Research indicates that two main factors contribute to these rear-end collision situations, 1) drivers adopting unsafe following distances, and 2) drivers not attending to the vehicle in front of them (Ben-Yaacov et al., 2002; Dingus, McGehee, Manakkal et al., 1997; Parasuraman, Hancock, & Olofinboba, 1997; Knipling, 1993). Drivers’ expectations and perceptual limitations underlie these types of rear-end collisions. For instance, with increased driving exposure, drivers learn that it is rare for large speed differentials to develop between their own vehicle and the one they are following (Ben-Yaacov et al., 2002; Dingus, McGehee, Manakkal et al., 1997). Perceptually it is also difficult for drivers to obtain and evaluate relevant cues regarding velocity and relative velocity, which leads to a reliance on expectations regarding “typical speeds” adopted by other drivers (Ben-Yaacov, Maltz & Shinar, 2002; Dingus, McGehee, Manakkal et al., 1997; Hoffmann & Mortimer, 1996). Drivers compensate for these perceptual limitations by obtaining information related to the lead vehicles relative position (whether the lead vehicle is “approaching or receding”) (Hoffmann & Mortimer, 1994). However, over time information related to vehicle presence may be lost as drivers adapt. These factors make it difficult for drivers to identify the situation as hazardous when confronted with a lead vehicle at rest or one that is slowing down (Ben-Yaacov et al., 2002; Dingus, McGehee, Manakkal et al., 1997).


Crossing Path Crashes
According to Najm, Smith, and Smith (2003), in 1998, approximately 1.72 million crossing path crashes occurred in the United States. Crossing path crashes occur when one vehicle cuts through the path of another. The vehicles in these situations initially approach from the side or from the opposite direction, colliding at a point of junction (Najm, Smith and Smith, 2003). Five main scenarios were identified:
1. Straight Crossing Path (SCP)

2. Left Turn Across Path – Opposite Direction Conflict (LTAP-OD)

3.Left Turn Across Path – Lateral Direction Conflict (LTAP-LD)

4.Right Turn Into Path (RTIP) crashes constitute 5.7% of all crossing path crashes and account for 99,000 crashes. In the year 1998, 2,000 of these crashes resulted in rear-end collisions (Najm, Smith et al., 2003). Common citations given to the drivers involved in these collisions include: alcohol or drugs, failure to yield right of way, running a traffic signal or stop sign, and speeding. In 5.5% of the cases, the driver turning was reported to be distracted, while in 5.1% of the cases the driver heading straight was distracted.

5.Left Turn Into Path (LTIP)crashes represent 5.9% of all crossing path collisions and constitute 102,000 crashes. In 1998, 3,000 of these crashes resulted in rear-end collisions (Najm, Smith, & Smith, 2003). Common violations charged to the drivers involved in this crash configuration include: alcohol or drugs, failure to yield right-of way, and running a traffic signal or stop sign.


Lane-Change Crashes
According to Sen, Najm, and Smith (2003), in 1999, approximately 539,000 lane change crashes occurred in the United States. Lane change crashes typically represent collisions in which “one vehicle encroaches into the path of another vehicle initially on a parallel path with the first vehicle and traveling in the same direction” (Sen, Najm, and Smith, 2003, p.1). To be labeled as a lane change crash two criteria must be met: 1) vehicles are required to initially be headed in the same direction and traveling on parallel paths and 2) “the encroachment, whether intentional (as in a typical lane change) or unintended (as in drifting), is the first in a sequence of events leading to the crash” (Sen, Najm and Smith, 2003, p.7). Two crashes result from lane change maneuvers, those that result in angle/sideswipe collisions and those that result in rear-end collisions.

Typical lane changes represent 38.4% of all lane change crashes. These scenarios consist of two vehicles proceeding on parallel paths, when one vehicle moves into the other lane and collides with the other. In 20% of these collisions, driver distraction was a contributing factor (Sen, Najm, & Smith, 2003). Drifting, the third most common scenario (11.5% of lane change crashes), denotes situations in which a vehicle traveling straight fails to maintain its position within its given lane. Common contributing factors include: alcohol, drugs, fatigue, drowsiness, and inattention. Approximately 7,000 drifting crashes result in rear-end collisions. Driver distraction was involved in 10% of these types of collisions.
In 1999, approximately 26,000 (4.7% of all lane change crashes) angle sideswipes and rear-end collisions resulted when a vehicle leaving its parking stall to enter a lane struck or was struck by an approaching vehicle (Sen et al., 2003). These collisions tend to have large speed differentials because the vehicle entering the lane is “starting from rest” (Sen, Najm and Smith, 2003, p. 11). Sen, Najm, and Smith (2003) indicate that in over 30% of collisions that fell within this crash configuration, the driver was distracted.

Key Terms

References

1. Ben-Yaacov, A., Maltz, M. & Shinar, D. (2002). Effects of an in-vehicle collision avoidance warning system on short- and long-term driving performance. Human Factors, 44(2), 335-342.
   
   
2. Dingus, T.A., McGehee, D.V., Manakkal, N., Jahns, S.K., Carney, C. & Hankey, J.M. (1997). Human factors field evaluation of automotive headway maintenance/collision warning devices. Human Factors, 39(2), 216-229.
   
   
3. Hoffmann, E. R., & Mortimer, R. G. (1994). Drivers estimates of time to collision. Accident Analysis and Prevention, 26(4), 511-520.
   
   
4. Knipling, R. R., Mironer, M., Hendricks, D. L., Tijerina, L., Everson, J., Allen, J. C., & Wilson, C. (1993). Assessment of IVHS countermeasures for collision avoidance: rear-end crashes (DOT HS 807 995). Washington, DC: National Highway Traffic Safety Administration.
   
   
5. Najm, W.G., Smith, J.D. & Smith, D.L. (2003). Analysis of Crossing Path Crashes. Performed by John A. Volpe National Transportation System Center, Cambridge, MA, Sponsored by National Highway Traffic Safety Administration, Washington D.C, March 2003, DOT HS 809 423
   
   
6. Najm, W.G., Wiacek, C.J., and Burgett, A.L. (1998). Identification of Pre-Crash Scenarios for Estimating the Safety Benefits of Rear-End Collision Avoidance Systems. Fifth World Congress on Intelligent Transport Systems, Seoul, Korea, October 1998.
   
   
7. Parasuraman, R., Hancock, P.A. & Olofinboba, O. (1997). Alarm effectiveness in driver-centered collision-warning systems. Ergonomics, 40(30), 390-399.
   
   
8. Sen, B., Campbell, B.N., Smith, J.D., Najm, W.G., “Analysis of Light Vehicle Crashes and Pre-Crash Scenarios Based on the 2000 General Estimates System“, Performed by John A. Volpe National Transportation System Center, Cambridge, MA, Sponsored by National Highway Traffic Safety Administration, Washington D.C, November 2002, DOT HS 809 573
   
   
9. Sen, B., Najm, W.G., & Smith, J.D. (2003). Analysis of Lane Change Crashes. Performed by John A. Volpe National Transportation System Center, Cambridge, MA, Sponsored by National Highway Traffic Safety Administration, Washington D.C, March 2003, DOT HS 809 571
   
   
10. Sullivan, J.M., & Flannagan, M.J. (2003). Risk of fatal rear-end collisions: Is there more to it than attention? Proceedings of the Second International Driving Symposium on Human Factors in Driver Assessment, Training and Vehicle Design. Park City, Utah, USA.