Welcome signs at the Naperville city limits advertise the population (144,560), an overnight street parking ban and something far less typical: the town's status as "A Red Light Photo Enforced Community."

Naperville is one of the rare cities that posts warnings about red-light cameras at its borders, even though research shows it makes the cameras more effective in preventing crashes.

Much of the debate over traffic cameras centers on whether they are genuine safety devices or money-raising gimmicks for municipalities. But a 2005 Federal Highway Administration study found they were more effective at curbing potentially dangerous incidents of red-light running if drivers heading into town were put on notice that somewhere down the road a traffic camera might be lurking.

It's an easy and inexpensive enhancement, yet rare is the area community that does it -- giving more ammunition to the skeptics who argue that the recent boom in traffic camera use is more about the ability to crank out automated $100 tickets than it is about saving lives.

The Tribune surveyed signage in two dozen of the Chicago-area towns that have switched on red-light cameras in recent years. Of those checked, every town had posted warning signs within a few hundred feet of cameras -- a state mandate at most camera-monitored intersections.

There is no similar requirement to post warning signs at the city limits, and Naperville was the only suburb in the Tribune's spot check that was in line with the federal recommendations.

Andy Hynes, a project engineer with the Naperville agency in charge of red-light cameras, said the signs had been installed at municipal boundaries on several larger roads heading into town.

At present, Naperville has only one set of operating traffic cameras at the intersection of North Aurora Road and Illinois Highway 59, but the City Council recently voted to add cameras at two more intersections: Illinois 59 and Diehl Road, and Ogden and Aurora Avenues. The signs were put in shortly after the camera at Aurora and Illinois 59 was installed early this year.

Hynes said the new cameras would be accompanied by the installation of more city-limit warning signs.

"The more times you're warned, the better," said Joseph Schwieterman, an urban transportation expert at DePaul University. "I think the signs put drivers on high alert that they better not take a chance, so they better err on the side of being cautious."

The federal study of crashes at 132 camera-monitored intersections in three states concluded that the devices had a "modest" effect in cutting down on crashes, with more signs translating into more safety.

"Warning signs located at both the treated intersection and at the city limits were associated with a larger benefit than warning signs at intersections alone," the study found.

Gauging the safety impact of red-light cameras is difficult. The Federal Highway Administration study gave the devices a qualified thumbs-up, but other studies have produced conflicting conclusions about whether they rendered intersections safer or more dangerous. Further muddying the picture is the fact that the ratio of traffic deaths to miles driven in the U.S. had been on a steady decline for decades before the emergence of cameras, thanks to improvements in traffic engineering and auto design.

Chicago began installing red-light cameras in 2003, and three years later the phenomenon arrived in the suburbs. Some communities claim the cameras have contributed to a drop in the kind of broadside crashes where red-light running is a factor.

Most cameras in Illinois require state permits, and as a pre-condition the Illinois Department of Transportation requires installation of bigger and brighter LED traffic lights at the intersections to be monitored by cameras. Better lighting, like better signage, is a deterrent to red-light running, making it difficult to sort out when accidents decline whether more credit should go to the new cameras or lights.

It's well understood that drivers exercise more caution at intersections when they can see a police cruiser. The underlying premise of camera enforcement is that fear of getting a ticket generated by an electronic snoop will produce the same effect.

Safety experts agree that traffic cameras perform best at reducing crashes when drivers are aware of their presence. On the other hand, they generate more revenue when less easy to spot.

In the United Kingdom, where cameras abound and nab speeders as well as red-light runners, cameras are typically painted a bright yellow or in a striped pattern to stand out.

But most cameras in Chicago and the suburbs are painted gun-metal gray or deep pewter and tend to blend into the background.

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