The effect of law enforcement deployment patterns on motorists\ubf speeds.

PDFTech ReportFHWA-OR-DF-04-04SPR 304 - 161Law enforcement85th percentile speedTraffic speedTraffic safetySpeed limitsData analysisEvaluationPolice patrolOregonOregon. Dept. of Transportation. Research UnitHaas, K. J.Jones, BarnieKirk, Alan R.Oregon. Dept. of Transportation. Research UnitUnited States. Federal Highway AdministrationUS Transportation CollectionThe combination of increased demands on Oregon\u2019s transportation system and limited law enforcement resources has led the Oregon Department of Transportation (ODOT) to investigate whether a relationship exists between motorists\u2019 speeds and law enforcement levels. If an optimum level of law enforcement could be identified that reduces the number of motorists driving in an unsafe manner, the end result could be a more efficient deployment of scarce law enforcement resources.This study deployed enhanced law enforcement patrols at six study sites in Oregon to evaluate the effects of law enforcement presence on vehicle speeds. Investigators first recorded baseline speeds for a two-month period prior to the commencement of enhanced enforcement. Enhanced patrols varied from 10 to 25 hours per week on either fixed or random schedules. Enforcement at each site was on an eight-week cycle: two weeks of enhanced patrols followed by six weeks of normal patrols.The data analysis compared median and 85th percentile speeds in the baseline and enhanced enforcement conditions. Baseline and enhanced enforcement data were also compared for the percent of vehicles traveling over the posted speed at each site. The findings showed that enhanced patrols resulted in small but statistically significant reductions in speed at most of the test sites. Both median and 85th percentile speeds were significantly higher than posted speeds at all of the study sites in both the baseline and the enhanced enforcement conditions