no43 2003
Why Do Rear-end Collisions Occur? Contributing Driver Errors -

  In 2002, the number of injuries in traffic accidents dropped below that of the previous year, although only slightly, thanks to various traffic safety measures. The annual number of injuries, however, remains unchanged at close to 1.2 million, about 90% of which are slight injuries. Changes in number of slight injuries by road user type are shown in Figure 1. Injuries to motor vehicle occupants account for the majority of slight injuries, comprising 64% of all slight injuries in 2002.
  From the classification of number of slight injuries among motor vehicle occupants by type of accident (Figure 2), we see that rear-end collisions account for the largest proportion (55%), much higher than the second-place crossing collisions (21%). The study of measures focused on the prevention of rear-end collisions between motor vehicles is therefore considered to be a key factor in reducing the number of slight injuries.
  However, to reduce the number of slight injuries is one thing; to eliminate them altogether is quite another.
  In addition to studying measures that will reduce injuries, ways to prevent accidents before they happen - so-called active safety measures - must also be investigated. We analyzed the conditions that give rise to rear-end collisions between motor vehicles, using the comprehensive database on traffic accidents and in-depth investigation of traffic accidents and with particular focus on the errors of drivers who cause such collisions. The results of that analysis are introduced in the following.
Fig. 1  Changes in Number of Slight Injuries by Road User Type /Fig. 2  Number of Slight Injuries by Type of Accident (2002)

1.Characteristics of Rear-end Collisions Based on the Comprehensive Database on Traffic Accidents Characteristics observed in rear-end collisions between motor vehicles are introduced in this section.
2.Analysis of Driver Errors Based on the In-depth Investigation of Traffic Accidents

  Preventing Rear-end Collisions
  The following measures are thought to be effective in preventing rear-end collisions between motor vehicles.

(1)Careful drivers
a.  To avoid rear-ending another vehicle
  *  Do not look aside from the road or think about things other than driving, especially when there appears to be no danger for the time being.
  *  Choose a vehicle speed and safe distance between vehicles so that you will have enough time for perception, decision-making/prediction, and operation/action without panicking, even if the preceding vehicle (rear-ended vehicle) has no working brake lights or turn signal indicator or other unforeseen circumstances occur.
  *  Keep in mind that other drivers will apply the brakes or signal a turn at different times than you would.
b.  To avoid being rear-ended
  *  Apply brakes and signal turns in good time. (In addition to encouraging the driver of the trailing vehicle to take avoidance actions, this will have a stimulating effect on the other driver, causing him to regain his mental focus.)
  *  Turn on the hazard warning lamp when you are stopping at the tail end of a traffic jam.

(2)Road environments and systems conducive to preventing rear-end collisions
a.  Reduce the number of danger zones by centralizing the entrances and exits of frequently used roadside facilities such as gas stations, restaurants, and convenience stores.
b.  Eliminate openings in center strips.
c.  Introduce and promote the use of dilemma-sensitive type traffic signals that control the amber traffic light in order to avoid the so-called "dilemma zone," where drivers of vehicles going through an intersection are not sure whether to stop or drive through the intersection.
d.  Popularize the use of rear-end collision warning systems that include a tailgating alarm. Recently, vehicles equipped with such systems have started to be produced, but these systems are designed to work well with careful drivers who might need them in case of unexpected incidents. Therefore we should not become too dependent on or overconfident in the system.

Institute for Traffic Accident Research and Data Analysis (ITARDA)