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Evaluation of automated speed enforcement in Montgomery County, Maryland

Retting, Richard A.; Farmer, Charles M.; McCartt, Anne T.
Traffic Injury Prevention (TIP)
October 2008

Objectives: Almost one quarter of speeding-related fatalities occur on streets with speed limits of 35 mph or less. In 2007, Montgomery County, Maryland, implemented the state's first automated speed enforcement program, with camera use limited to residential streets with speeds limits of 35 mph or less and school zones. The purpose of the present study was to evaluate initial effects of camera enforcement on traffic speeds and to assess public attitudes.
Methods: Vehicle speeds were measured approximately 6 months before and 6 months after speed cameras were deployed and warning signs were installed. Speed data were collected on a sample of roads with and without camera enforcement in Montgomery County, as well as on a sample of roads in a comparison community that did not have speed cameras. In addition, telephone surveys were conducted in Montgomery County.
Results: Relative to speeds of drivers on roads in the comparison community, the proportion of drivers in Montgomery County traveling more than 10 mph above posted speed limits declined by about 70% at locations with both warning signs and speed camera enforcement, 39% at locations with warning signs but no speed cameras, and 16% on residential streets with neither warning signs nor speed cameras. Public opinion surveys found 74% of Montgomery County drivers thought speeding on residential streets was a problem. Six months after enforcement began, 60% of drivers were aware of the camera program and 62% supported it.
Conclusions: The camera program was effective at reducing speeding on targeted streets. The finding of speed reductions beyond targeted locations is evidence that highly visible automated enforcement can promote community-wide changes in driver behavior. Although a majority of drivers supported automated speed enforcement, about one third opposed it. Jurisdictions planning to implement speed cameras should draw on international experience to anticipate controversies that generally arise and take steps to address them.