Before the city of Scottsdale, Arizona, kicked off a pilot speed-camera enforcement program, 15 percent of drivers were traveling faster than 75 mph on sections of a busy urban freeway with a 65 mph posted limit. Once the cameras were in place on Loop 101, the number of violators plunged to 1-2 percent, a new Institute study reveals.
What's more, speed violations fell on the same freeway 25 miles outside of the enforcement area. Surveys also indicate that speed cameras garnered the support of local drivers.
"These results show how the combination of highly visible warning messages and camera enforcement deters speed violations," says Richard Retting, Institute senior transportation engineer and the study's lead author. "The program wasn't about tickets. The goal was to drive down violations by sending a message that speeding is unacceptable. Scottsdale's program is one of the best examples we've seen of how to accomplish that."
In early 2006 Scottsdale began a 9-month pilot program to evaluate speed-camera enforcement on an 8-mile stretch of a busy urban freeway, becoming the first U.S. locality to use fixed devices on a major highway. Fixed devices don't require manpower, while mobile cameras are attended by police officers and can be moved among locations. About 35 U.S. jurisdictions use speed cameras.
Whether fixed or mobile, speed cameras monitor traffic speeds and photograph vehicles going faster than specified speeds, usually well above posted limits. Along with a picture of the offending vehicle, the cameras record the date, time, location, and vehicle's speed (see "Speed camera programs in Australia and Britain present useful lessons," Sept. 28, 2005).
In Scottsdale, cameras at 6 sites photographed vehicles going 11 mph or more over the 65 mph speed limit on Loop 101, a 6-lane freeway encircling the Phoenix metro area. Citations were mailed to registered vehicle owners.
Institute researchers collected independent data at several locations in the city's enforcement zone. Speeding decreased among both passenger vehicles and large trucks, with the combined proportion of vehicles exceeding 75 mph dropping to 1-2 percent while the cameras were in use from 15 percent ahead of camera enforcement. The proportion fell to 2 percent from 16 percent for cars and to 1 percent from 9 percent for trucks.
Average speeds in the enforcement area declined to 63 mph soon after the program began from 70 mph beforehand, remaining around 65 mph, the posted speed limit, during the pilot program. Immediately after it ended and camera enforcement stopped, average speeds increased to 69 mph, and 12 percent of drivers were going faster than 75 mph.
By comparing Loop 101 speeds with speeds on nearby freeways that didn't have cameras, researchers concluded that the Scottsdale program was associated with as much as a 95 percent decrease in the odds that drivers would surpass 75 mph. Previous studies in Europe and Australia, where speed cameras are widely used, have reported 50-60 percent reductions in the proportions of vehicles exceeding speed limits by more than 9 mph.
Speed violations of 11 mph or more also declined on another section of Loop 101 about 25 miles away in Glendale, Arizona, where cameras weren't used. Freeway drivers traveling through Glendale slowed down an average of 5 mph soon after Scottsdale's speed camera program began and kept their speeds in check until camera enforcement ended.
"We were surprised to see speeds decline so far away from the pilot enforcement area," Retting says. "Drivers seem to have associated Loop 101 with speed cameras, not just certain stretches of the freeway, maybe because in Scottsdale itself, prominent signs alerted drivers that speed-camera enforcement was under way and the pilot program attracted lots of attention from the media."
Still, Retting notes, 1-2 percent of drivers continued to exceed the posted limit by 11 mph or more during the pilot. And once it ended speeds quickly increased, indicating that without camera enforcement drivers revert to their old habits.
Mary Manross, mayor of Scottsdale, points out that "as soon as our demonstration program launched, the results were dramatic. Our program clearly worked. Throughout the process — from discussion to implementation, right through to the analysis — surveys indicated a solid majority of Scottsdale residents supported the freeway photo-enforcement demonstration program. Experience in Scottsdale was so positive that Governor Janet Napolitano directed the Arizona Department of Transportation to devise a statewide program of photo enforcement."
The majority of Scottsdale drivers the Institute surveyed by telephone about the camera enforcement program agreed that speeding was a problem. They were aware that cameras were in use on Loop 101, and they supported the pilot. These responses are in line with a 2007 Insurance Research Council survey finding that about 60 percent of U.S. drivers support speed cameras.
Speed-camera enforcement was reinstated on the Scottsdale section of Loop 101 in February 2007.