Since the installation of speed cameras throughout Baltimore city in the fall of 2009, the annual revenue generated by the $40 tickets issued to motorists caught traveling 12 miles per hour over the limit has increased nearly tenfold — from just $2.4 million in 2010 to $19.2 million over the past 12 months. That increase in revenue is partly due to the number of speed cameras jumping from 28 to 56 to 83 over the course of the program. But it can hardly account for all of it. And anyway, if the speed cameras are intended to deter motorists from speeding, the revenue should be going down, at least per camera.

Mayor Stephanie Rawlings-Blake is defending the speed cameras’ function as something other than a money-maker. “If you take a look at other jurisdictions, their revenue trends downward,” Rawlings-Blake said. According to the Sun, the mayor expects Baltimore’s speed camera revenue to drop next year.

But Councilwoman Mary Pat Clarke wonders how the stated intention of slowing down motorists squares with the practice of moving some of the cameras from location to location. In her view, the cameras have to stay in one spot for drivers to learn to slow down in those locations, and her opinion is supported by the fact that the eight portable cameras account for an inordinate amount of revenue.

The city expects to collect only $11.4 million from speed cameras next year, $7.5 million the year after that, and $6.9 million the year after that. We’ll see.