Stop-light cameras cut violations a lot, wrecks a little, new study says
Posted on Feb 5, 2010 in Traffic
An independent study of Jefferson Parish’s stop-light cameras, which were switched off last week amid disclosures of payments to the contractor’s lobbyist, provides new evidence that they reduce violations and collisions.
red_light_camera_sign.JPGJohn McCusker / The Times-Picayune archiveThe study was conducted by doctors from Tulane and Louisiana State universities’ medical schools and is scheduled for publication in March. It is the only known objective evaluation of the camera program’s effectiveness; Jefferson Parish officials, while touting the cameras and the resulting traffic tickets as a public safety initiative when they launched the program two years ago, never conducted their own study.
The Tulane-LSU team sifted through eight months of data from the intersection of Veterans Memorial Boulevard at Clearview Parkway in Metairie and determined that the cameras reduced the number of stop-light violations by 69 percent. They also found a slight drop in the number of collisions, although that trend is more difficult to track, said Dr. Georgia Wahl, a Tulane surgical resident and lead researcher for the study.
“It’s very hard to say if there’s a cause and effect with decreasing the amount of accidents. Was it by chance? Was it the red light, or people slowing down? We don’t know,” Wahl said. “But it (the traffic camera) does change long-term behavior.”
Traffic cameras started photographing stop-light violators at 11 Jefferson Parish intersections and generating citations in October 2007, after a four-week trial period. They recorded 270,344 violations as of Jan. 27, when the Parish Council suspended the program. Councilman Chris Roberts asked for the vote after discovering that the contractor, Redflex Traffic Systems of Phoeniz, Ariz., intended to direct a cut of its revenue from the ticket fines to lobbyist Bryan Wagner.
By then, the doctors at Tulane and LSU had already penned their report, which is scheduled for publication next month in the Journal of Trauma, Injury, Infection and Critical Care in March, Wahl said.
The team collected statistics on the Veterans-Clearview cameras from the parish government, Redflex and the Sheriff’s Office, including the number of warning letters, citations and collisions between Sept. 23, 2007 and June 30, 2008.
The researchers noticed a huge dip in stop-light running, especially after the four-week warning period during which drivers received a letter but no citation. The cameras averaged 2,428 violations per week during the warning period but only 356 per week in June 2008.
What most struck researchers was the effect on repeat offenders, Wahl said. Out of the 30,441 drivers who received warning letters or citations, only three ran the Veterans-Clearview signal more than once.
“That was the biggest impact I found,” Wahl said.
The doctors noted 122 wrecks at the intersection in the 10 months before October 2007, falling to 97 in the 10 months after the citations started — not a significant reduction, according to the study.
Wahl said there are several problems with trying evaluate the cameras’ effects on collisions. The Clearview-Veterans intersection already had a high rate of wrecks, and the study didn’t distinguish the type of collisions that occurred, only the total number. Similar studies elsewhere in the United States have found cameras don’t reduce the total number of wrecks but do cut down on right-angle, or “T-bone”, collisions that generally cause more serious injuries.
“All we can scientifically say is there were (fewer) collisions,” Wahl said.
When they launched the camera program, parish officials touted them as a way to improve public safety. Critics said it was just a way for politicians to raise revenue.
Parish officials collected statistics on the citations and wrecks at each of the 11 intersections but never went through with plans to study the numbers. Engineering Director Mark Drewes said officials initially were waiting for a year’s worth of data, but they shelved plans for a study when more than 300 drivers banded together in January 2008 to challenge the constitutionality of the cameras in federal court.
“We were informed by the parish attorney’s office that it’s under litigation,” Drewes said. The department was told to keep collecting the data but “to halt and not to go forward with the study.”
U.S. District Judge Sarah Vance tossed the lawsuit last year, but the plaintiffs refiled it in state court in Gretna. That suit was dismissed in January by Judge Robert Pitre, but the plaintiffs plan to appeal.
In the meantime, violators have paid fines totalling $19.7 million, money to be split among Redflex and local government agencies. All the money is sitting in escrow, pending the end of the litigation.
Wahl said the idea for Tulane and LSU to study the cameras came about when one of her staffers received a citation in the mail.
“That kind of sparked it, to see whether or not it worked or changed behavior. No one from Redflex or Jefferson Parish ever asked us; we approached them,” she said.
The doctors’ study might not have shown a significant dip in wrecks, but Wahl said the cameras have had a positive effect: “We can scientifically say that people change their behavior at these red light intersections.”