Mayor Catherine Pugh’s acknowledgment that she views the return of speed cameras to Baltimore’s streets, at least in part, as a revenue generator surely doesn’t sit well with those who got faulty tickets under the city’s old system. Some might also share Comptroller Joan Pratt’s concern that the new contract for red-light cameras is going to a renamed version of the same company that previously ran the error-prone speed cameras.

The revenue associated with speed cameras is the simple reality of a technology whose primary purpose can and should be increasing public safety around schools. There wouldn’t be any revenue if people weren’t speeding. But if the system is designed and deployed properly, it shouldn’t be a big moneymaker; in fact, it should offer diminishing returns as motorists’ behavior changes.

Last year, the Maryland comptroller’s office reported that the 45 counties and municipalities that employ the technology collected $57 million from speed cameras in 2015, $13 million less than they did two years before. (Baltimore’s speed camera program was largely shuttered in 2012 after a Sun investigation into erroneous tickets; it operated on a very limited scale in early 2013 before being shut down altogether that April.) Some jurisdictions actually lose money on their cameras. But that doesn’t mean they’re ineffective.

In Howard County, police report only modest revenue from speed cameras — just $372,000 more than the expense to run the program. But they also say they have seen a reduction in speeding on 70 percent of school zone roadways compared to the period before the county’s speed camera program began in 2011. Collisions on those roads are down 27 percent.

The same is true in Montgomery County, which has a larger and more lucrative program — including more than four times as many speed cameras as Baltimore plans to employ. An Insurance Institute for Highway Safety study from 2015 found that motorists were 59 percent less likely to exceed the speed limit by 10 miles per hour or more on roads with the cameras than they were on similar roads nearby in Virginia, where speed cameras aren’t allowed. The report also noted a 19 percent reduction in the likelihood of crashes causing injuries or death.

Montgomery County’s program is considered a national model — among other things, it has taken to regularly moving its cameras to different locations along enforcement corridors so motorists don’t get used to slowing down in one particular spot. If every community in America did the same thing, we’d see 21,000 fewer fatal or incapacitating accidents per year, the IIHS estimated. Baltimore’s old program, by contrast, had less discernible public safety benefits. The Sun’s Luke Broadwater reported in 2014 that the number of accidents resulting in injuries actually declined somewhat in the year after Baltimore’s cameras were shut down.

We suspect the reason is that Baltimore’s old cameras appeared to be deployed through the lens of revenue, not safety. Rather than picking the places where schoolchildren were most at risk, city officials placed many of them on busy, multi-lane corridors where speeders were plentiful.

Mayor Pugh is promising to announce the locations of the cameras in advance and to give drivers 30 days’ warning before issuing tickets. The public and City Council need to keep a close eye on the program to make sure the cameras are located in places where speeding puts kids’ lives at risk, not just those that will be lucrative, and they need to watch to make sure the program doesn’t grow beyond the city’s ability to effectively manage it. Before the old program was shut down, Baltimore had 83 speed cameras and 81 red-light cameras. Ms. Pugh is proposing 30 total: 10 red-light cameras, 10 fixed speed cameras and 10 portable speed cameras. We shouldn’t be in a rush to expand.

Finally, the council should follow Howard County’s lead and require detailed annual reports on the program’s activity, its effects on speeding, the number of prospective tickets that are rejected after review and the number that are overturned in court, among other data. Baltimore’s bad experience aside, speed cameras can be an effective tool to protect public safety. We just need to apply enough scrutiny to make sure they live up to that promise.