SAN JOSE — Legislation for a pilot program that would install speed-detecting cameras on the most dangerous traffic corridors in San Jose and San Francisco has been shelved after facing vociferous opposition and tepid support.

Assembly Bill 342 did not make it out of the Assembly Transportation Committee after a hearing held earlier this week. Assemblyman David Chiu, D-San Francisco, authored the bill, which was backed by co-authors that include former San Jose city council members Assemblyman Kansen Chu and state Sen. Jim Beall. Chiu said he plans to revise and bring it back to the statehouse in 2018.

Chiu’s bill also was supported by San Jose Police Chief Eddie Garcia and San Francisco Police Chief William Scott as well as their respective city governments.

“I look forward to continuing to refine it with Mayors Ed Lee and Sam Liccardo and the talented transportation professionals who work for both cities,” Chiu said in a statement. “We know that speed kills, and we believe that ASE will save lives. For the sake of Aileen and so many others, we won’t give up.”

The person Chiu referred to is 5-year-old Aileen Quiroz Chavez, who in May 2013 was walking with her sister and aunt near a school in South San Jose when they were hit by an SUV that was driving too fast for the school zone.

Traffic fatalities in San Jose have occurred at an elevated rate over the past five years, topped by a two-decade high of 60 in 2015. Last year, there were 50 traffic deaths in San Jose. San Francisco has recorded about 30 annually for the same period.

San Jose has been particularly troublesome on that front because of its sprawling geographic footprint that is traversed by high-speed thoroughfares and expressways that allow motorists to build up the kind of velocity that experts say exponentially increases the risk of major injury and death.

Garcia and Scott are themselves backed by assorted traffic-safety advocates in their respective cities, as well as the California Police Chiefs Association.

But just as many influential groups are either skeptical of or outright opposed to the speed-camera pilot. Groups like the ACLU worry about the privacy violations that the cameras pose, which the authors addressed by limiting photographs to license plates and setting strict limits on how long data is retained — presumably to prevent tracking a motorist’s movement over time.

Other critics say the prospective $100 fines levied on violators who go 10 mph above the prescribed speed limit are unfairly punitive to lower- and middle-class drivers compared to more well-to-do drivers who can more readily absorb the cost.

The most vocal opposition, however, came from police labor unions from throughout the state who criticized the cameras as a poor substitute for well-trained law-enforcement officers.

California Highway Patrol Officer Tom Maguire, speaking for the California Association of Highway Patrolmen, the agency’s rank-and-file union, challenged the basic premise for the cameras’ introduction.

“I have never investigated or assisted in an investigation that involved a vehicle and a pedestrian or a vehicle and a bicycle that resulted in a fatality where speed was the primary collision factor,” Maguire said. “Never.”

Maguire qualified his statement by contending that serious traffic collisions that injure pedestrians and bicyclists are primarily violations of crosswalk and bike-lane protections. Focusing solely on speed, he said, is “taking the easy way out” in forming lasting solutions.

But Jaime Fearer, deputy director for California Walks, cited no fewer than a half-dozen studies off the top of her head about the danger of speed on city roadways.

“The fact remains that speed is still the top indicator of whether you’re going to survive a crash. Period,” Fearer said. “Our bodies aren’t meant to be tossed around at that speed whether they are in a steel shell or not.”

Maguire also argued that the deterrent effect of a traffic stop by an officer, and the discretion of an officer in issuing a citation or a warning, are more effective methods of battling the problem.

“Ticketing alleged speeding vehicles by the tens of thousands is not addressing the cause of these collisions,” Maguire said. “Meaningful enforcement will exponentially increase the odds of gaining compliance that these cities seek on their roadways.”

Maguire also warned that ire over the automated tickets will be misdirected at him and other traffic cops.

“This in and of itself is a serious and credible threat to officer safety,” he said. “They won’t be mad at the local city government … they’re going to be mad at road officers like me.”

Garcia said he is puzzled by the law enforcement opposition. He backs the speed cameras as a supplement to an understaffed city force that has to focus on curbing violent crime.

“From my investigators, speed is a major cause here in San Jose,” he said. “Our primary function is not traffic enforcement, and we have to concentrate scarce resources. If this can help our secondary function of traffic enforcement, this is one way we can do it.”

Garcia also noted that nothing in the bill makes the cameras mandatory for any jurisdiction, and theorized that some of the opposition stems from a broader long-term worry.

“What are they afraid of? That it actually works? They don’t have to do it,” he said. “There is an irrational sense of a threat that this will somehow affect staffing in police departments. Never would I advocate for this program to be in lieu of officers, only in addition to. It would just enhance what agencies have.”