Development of an index to measure Police traffic enforcement effectiveness
The aim of the research was to develop a procedure that would measure traffic enforcement effectiveness levels for each Victoria Police Region. The development of this measure of effectiveness referred to as the Police Effectiveness Index or the Output Performance Index was achieved using structural time-series regression modelling techniques. Relationships were developed that connected monthly crashes in each of the five Police Regions with monthly variations in variables representing exposure, enforcement activity and other factors for 1989-1997. Crash and enforcement data were obtained from the Victoria Police. The models developed for each Region revealed the relative contribution of an increase in each enforcement operation to reducing the risk of casualty crashes. The reductions were found after the effects of exposure changes and other factors had been accounted for.
A monthly output performance index for each Region was developed for January-December 1998. There was some variation found in the monthly indices both between and within Regions. Relative to the previous year, 1997, the Police performed better than expected on average during the first quarter of 1998, but decreased their output performance for the rest of the year.
The value of the output performance index to Police is that it specifies which enforcement operations Police should increase their resources in per Region to reduce the risk of casualty crash. The index also allows for the assessment and comparison of the effect on road safety of different enforcement activities both within and among Police Regions. The application of a relatively new statistical analysis technique, structural time-series modelling, has offered increased power and flexibility in the modelling of crashes compared to traditional multivariate regression methods.