Fatal crashes involving young male drivers: a continuous time Poisson change-point analysis.

BACKGROUND

In an effort to reduce road trauma, the New Zealand government implemented a series of intervention programs over the last decade, with young male drivers as the main target audience. Previous research, however, found little or no evidence that these programs had any impact on this group of drivers despite an apparent decrease in their crash involvement.

OBJECTIVE

To determine the approximate time when the decrease in the number of fatal crashes involving young male drivers occurred.

METHOD

A Poisson change-point estimator was used to locate the most likely point where a decrease in the average number of monthly crashes had occurred.

RESULTS

The most likely time of change was found to coincide with the time when the Transport Act 1992 was debated and passed in Parliament. The publicity given to the issue and the Government's signal of impending actions were sufficient to induce a significant change in the behaviours of young male drivers.

IMPLICATIONS

This result can partially reconcile the difference between the apparent reduction in the number of fatal crashes involving young male drivers and the inability of previous studies to find a significant impact of the various intervention programs since the change occurred prior to the actual implementation of the programs. Nevertheless, it was argued that the implementation of the programs subsequently was necessary in sustaining the reduction.