Overtaking road-accidents: differences in manoeuvre as a function of driver age.

Nine-hundred and seventy-three police road-accident files describing overtaking accidents were sampled from the headquarters of Nottinghamshire Constabulary, England, for the years 1989-1993. Salient facts were extracted from each case, including the exact manoeuvre involved, the principle explanatory factors, the driver(s) most at fault, and the drivers' ages. Two kinds of reliability measure for case interpretations. indicated high levels of consistency. Two induced exposure measures were used, comparing driver involvement in a given type of overtaking accident with involvement in overtaking accidents in general, and comparing the age profiles of the drivers most at fault with those of the other drivers involved. Ten types of overtaking accident were distinguished, and three are discussed in detail: collision with a right-turning vehicle (the most common injury-accident for overtakers), which tends to occur either because a young driver makes a faulty overtaking decision, or an older driver makes a faulty right turn; head-on collision, which affects all age groups roughly in proportion to exposure; and the 'return-and-lose-control' accident, which is associated particularly with young drivers. The study illustrates the 'structured judgement method' of accident causation research, in which human interpreters are used to ascribe causes and processes to individual cases, but orthodox research techniques are used to standardise procedures, and to assess and ensure reliability.