The Victoria Police requested MUARC to develop a procedure that would measure traffic enforcement outcome levels against expected levels for each Victoria Police Region. To achieve this objective, relationships were developed that connected monthly casualty crashes in each of the five Police Regions with monthly variations in variables representing exposure, enforcement activity and other factors measured in each Region for the period 1989-1997. These relationships were achieved using structural (`state-space') time-series regression modelling techniques. An index for each Region was developed for the months January-December 1998 using the monthly average during 1997 as the base period. These were tested against actual road safety performance by comparing the observed crash frequencies per month with the expected levels (projected from the estimated models). This testing procedure appeared to work best when Police were performing better than average (as measured by the index), with reductions in casualty crash risk occurring in most cases. This was even more evident when the current month's index was compared with the next month's crash risk outcomes. (Author/publisher)
Abstract