Chattanooga Police Department Officer Tom Coleman sits in the back of a white van parked alongside Amnicola Highway.

A camera the size of a small suitcase is perched over his left shoulder as his eyes flit back and forth between two computer screens.

One screen shows a view of traffic passing by outside but has a small digital red square superimposed on it. The other shows a Web page with a list of citation categories and links to file a traffic ticket based on what the camera captures.

The camera snaps photos when the red square turns green on the computer screen.

"Once these take them, they're uploaded," Officer Coleman says.

Police and traffic engineers in Chattanooga are citing speeding motorists and at the same time gathering data for the Tennessee General Assembly, whose members are crafting a bill that could place a moratorium on traffic cameras.

If the proposed moratorium passes, new cameras and contract renewals would be prohibited for two years. Chattanooga's cameras are contracted through Lasercraft, a Norcross, Ga.-based company.

The company handles maintenance, training and upgrades for red-light cameras, traffic cameras used as the city's fixed speed cameras and the mobile speed vans. Lasercraft collects a percentage of each fine issued by each device.

Chattanooga signed the Lasercraft contract in October 2006, and the agreement is up for renegotiation in the coming weeks.

INSIDE THE VANS

In the city's four speed vans, patrol officers sit for eight hours a day, checking citations and adjusting the cameras to the right height to capture license plates.

Sgt. Gary Martin, who heads the speed van program for the police department, said the officers work closely with city traffic engineers, who review crash and citation data to see where most problems arise.

He said he hears plenty of complaints during monthly city traffic court hearings -- including that drivers didn't see the signs, which are not required, and that the cameras are unfair because there isn't any interaction with police.

During a standard traffic stop, however, other violations can crop up quickly, such as not wearing a seat belt or reckless driving, and that would increase fines, Sgt. Martin said.

Police also get lots of calls from residents who want the vans used to cut down speeding in their area, he said, but that's not always feasible.

"Sometimes you may want the speed van in your neighborhood, and we go out there and look, and it's just not possible. There's just nowhere for us to set up," Sgt. Martin said.

A BREAK FOR DRIVERS

What many drivers don't realize, Sgt. Martin said, is that if they get a speeding citation from the vans or other camera, it will cost much less than if an officer writes the ticket.

Speeding fines for all the devices in Chattanooga are set at $50, whether the driver pays it or chooses to appear in court. In comparison, a ticket issued by an officer costs $119 plus court costs if the driver decides to dispute it, according to city court personnel.

Though the camera captures speeding incidents, police must approve the citations.

"I've had them knock on the van and ask, 'Hey, did I just get a ticket?'" Officer Coleman said.

Each year, city traffic employees sift through an annual report to see, based on accidents and citations, where motorists need to slow down, said John Van Winkle, city traffic engineer.

"Chronic speeding increases the risk of someone making a mistake," he said.

On the Hixson Pike S curves, police have seen a 90 percent reduction in violations since the installation of cameras in 2006, Mr. Van Winkle said. The road was exempted from the legislature's proposed moratorium.

"We had four accidents last year. There were 100 in 2001," he said.

He said the officers move vans as needed. Drivers call both his office and police to complain that the vans are on certain roads too often, he said.

"If we've changed driver behavior, then we'll go somewhere else," Mr. Van Winkle said.