Various measures to reduce injuries suffered in traffic accidents have succeeded in reducing the numbers of dead and severely injured in accidents. On the other hand, the total number of accidents, the majority of which result in minor injuries, continues to increase. In order to reduce the number of accidents, in future we shall have to address their occurrence per se. In other words, our analysis and countermeasures will need to be made from the standpoint of prevention and safety.
We report here on our analysis of the characteristics of errors observed in traffic accidents on the basis of a survey of 300 accidents that occurred in 1997.
  Characteristics of Human Errors Observed in Traffic Accidents
  1.1 Errors of Perception: Carelessness and mistaken assumptions
  1.2 Errors of Decision-making and Prediction: Mistaken assumptions
  1.3 Errors of Operation: Flurry, panic and mistaken assumptions
  Sample 1
  Sample 2
  Sample 3
  Sample 4

  Below is our summary of the characteristics of human errors and key contributing factors for preventing errors and their repetition.
(1)Most errors occur in the stages of, first, perception and then judgement and prediction, and few in the stage of operation.
(2)There are 2-3 errors per party to an accident; in other words, there are two or more opportunities to avoid the accident.
(3)There is a high incidence of failure to notice travellers on perpendicular paths, for reasons primarily of carelessness, consisting of reduced levels of concentration on driving, and failure of identification due to the mistaken assumption that there oughtn't to be anyone up ahead, followed by obstructions of view, as caused by buildings, shade of other vehicles or poor weather. In other words, these are errors of "I would have seen it if I looked, but I didn't," followed by errors of "I wouldn't have seen it even on the lookout" (obstructions of view).
(4)On the other hand, drivers rarely fail to notice intersections per se, and there are more than a few cases in which drivers, having identified an intersection, do not assume "there won't be anyone on the intersecting road," but managed to recover from errors of perception with respect to a traveller on a perpendicular path through the safety-oriented decision-making and prediction that "there might be someone on the intersecting road" and taking care to drive defensively.
(5)Education with emphasis on the following points would seem to be of importance in preventing these errors:
a. When driving, concentrate above all on driving
b. Always look for other vehicles at a stoplight or other intersection entailing a temporary stop, even when you have the right of way
c. At intersections with an obstructed view and no one visible, assume that there might be someone there, even if I can't see him, not simply that nobody's there

Institute for Traffic Accident Research and Data Analysis (ITARDA)