The D.C. Council chairman wants to know whether the District is growing overly reliant on traffic camera revenue, as it expects to add another 91 camera locations in the coming fiscal year.

Mayor Vincent Gray's proposed budget counts on an additional $31.7 million in revenue from the new traffic camera locations, according to the city's chief financial officer. Those cameras could be used to extract fines from drivers who roll through stop signs or speed up to beat a red light.

The Metropolitan Police Department's total automated enforcement program is expected to bring in about $67 million next fiscal year, down from a projected $81.3 million this year, according to the mayor's proposed budget.

AAA Mid-Atlantic spokesman John Townsend questioned that assessment, arguing that the city chronically underestimates the money it will earn from traffic enforcement cameras. Townsend said that at the city's current rate, the District would bring in $120 million this fiscal year.

During a hearing Monday on the mayor's budget proposal, D.C. Council Chairman Phil Mendelson asked Gray whether the city was relying on funding from traffic cameras to that it would need to conduct a formal study to see how much revenue would be lost if the speed limit were raised.

Gray said that the city had decreased the speed limit in some areas and then said, "I'm reminded of an incident that happens a couple months ago on Florida Avenue," where a woman was struck by a speeding car.

"I'm not sure you've answered my question," Mendelson said. "But my time's expired."

At-large Councilman David Grosso picked up the baton, saying "It would be good to know what kind of public good [traffic cameras are] serving."

Grosso called for a formal study of traffic cameras' effectiveness in the District.

Russ Rader, a spokesman for the Insurance Institute for Highway Safety, said national research showed that traffic cameras reduce crashes over time.

"Research around the world show that red light cameras reduce red light running violations by 40 to 50 percent and reduce injury crashes by 25 to 30 percent," Rader said.

As traffic cameras reduce car crashes, revenues tend to decrease with them, he said.

"They generate a lot of revenue especially at first because a lot of people break the law," Rader said. "But, if you're concerned about giving money to the government through tickets, then don't run the red light."