A proposal to bring speed cameras to Roosevelt Boulevard got a boost this week from a federal report encouraging states to approve the devices to make roads safer.

The report, issued Tuesday by the National Transportation Safety Board, "is decisive evidence that automatic speed enforcement is a critical tool we should apply towards preventing deaths and serious injuries," Mayor Kenney said in a statement.

The NTSB report stated that 36 states, including Pennsylvania and New Jersey, do not use speed cameras. But the Pennsylvania legislature is considering two bills to authorize limited use of them in work zones and on the Boulevard, long considered one of the most dangerous roads in the city. If the bills pass, the cameras would photograph vehicles traveling at least 11 mph over the speed limit, and the owner would be mailed a ticket. The Boulevard would have up to nine speed cameras along nearly 12 miles, advertised by warning signs every two miles.

The bill to authorize a speed camera pilot program for the Boulevard has been introduced in the House and moved out of committee. A Senate bill to authorize speed cameras in work zones has been referred to the House Transportation Committee.

State Rep. John Taylor (R., Phila.), a sponsor of the Roosevelt Boulevard bill, expects to combine it with the Senate bill. The NTSB study, he said, will go a long way toward convincing other legislators that speed cameras are a critical safety tool and not just a way to generate revenue, a complaint others have had about the technology.

"Members see this study, and it will give something of a defense," Taylor said Thursday. "This really isn't about revenue. I hope we don't make one cent and people just slow down."

The NTSB study sought to evaluate the part speeding played in car crashes and what could be done. From 2005 to 2014, speed played a role in 31 percent of American traffic fatalities — 112,580 deaths, the study stated. States that have authorized speed cameras include Illinois, Louisiana, and Maryland.

Speed cameras slow down traffic and save lives, said Ivan Cheung, an NTSB transportation research analyst who worked on the latest study. A 2010 review of data from around the world found that speed cameras had reduced the number of all crashes by 49 percent and serious injuries and deaths by 44 percent, he said.

But other studies counter the NTSB findings. Jim Walker of the National Motorists Association cited a 2008 study by the National Highway Traffic Safety Administration that found speed was a cause of about 13 percent of crashes reviewed.

Speed cameras exist to generate money, not improve safety, he said.

"They have to write a lot of tickets, or they lose big money," said Walker, of Ann Arbor, Mich., which does not use speed cameras. "A city won't use speed cameras that lose big money."

Cheung agreed that the perception of speed cameras as a scam or "gotcha" tool damaged their credibility, and said states should clearly mark areas where speed cameras are in use and inform the public on why they are being used.

The NTSB study also questioned the standard used to set speed limits across the country, saying that in areas busy with development or foot traffic, speed limits may be set too high.

Walker again disagreed with the NTSB findings. Speed limits are often set too low, he said, and adjusting speed limits had a minimal effect on how fast drivers traveled.

Typically traffic engineers determine the speed 85 percent of vehicles travel on a given road and base limits on that speed. The system is grounded in 1940s and 1950s studies on rural or arterial roads.

"You really should look at it holistically, giving other factors the same kind of treatment … pedestrian activity, the history of crash statistics," Cheung said.