Spatial Relationships between Alcohol Outlet Density and Alcohol-Related Motorvehicle Crashes

Background

Spatial relationships between alcohol outlets and motorvehicle crashes are not well understood. Greater densities of outlets provide greater availability of alcohol, potentially leading to more drunk driving and more crashes; while at the same time reducing driving distance between outlets and destinations, potentially leading to fewer crashes. This study examined spatial relationships between crashes and outlet densities in local and spatially lagged areas of Melbourne, Australia.

Methods

A Bayesian conditional autoregressive Poisson model predicted counts of non-fatal alcohol-related motorvehicle crashes in 9,214 SA1 census areas (mean population = 415.2). Cases were all ambulance-attended crashes occurring between 2010 and 2012 in which paramedics noted the patient was alcohol affected (n = 2,056). The main dependent measures were the densities of bars, restaurants, and off-premise alcohol outlets per square kilometer in local and lagged (adjacent) SA1 areas. To account for differences in overall crash risks between areas the model expectancy was a count of all crashes over the study period. We also adjusted for areal demographic characteristics (proportion male, socio-economic status, median age), zoning (proportion retail), and roadway characteristics (total kms, proportion highway, proportion arterial).  

Results

Relationships between greater densities of outlets and alcohol-related crashes were not detected in local SA1 areas, however lagged SA1 areas with one additional bar per square kilometer (i.e. an 85% increase compared to the study area mean) had 27% greater incidence of alcohol-related crashes (IRR = 1.267; 95% CI: 1.013, 1.633).

Conclusions

Policy limiting bar density may lead to fewer alcohol-related crashes in adjacent areas.