As I was walking back from yesterday’s disaster simulation at RFK Stadium, I noticed a SUV parked alongside Independence Avenue as it headed east across the Anacostia River. But this wasn’t just any car — it was one of the District’s new mobile speed cameras.

In late August, the Metropolitan Police Department announced that it would be installing 19 new speed cameras around the city. But partially as a recognition that drivers eventually get to know where they should slow down, all but four of the speed cameras are mobile, contained within marked and unmarked police vehicles and able to set up wherever the need — or potential revenue — is highest.

Currently, the District has 19 fixed speed cameras and 56 mobile speed cameras, including the new batch installed in September. (All the locations are here.) Police claim that they promote safer driving, but on their website, they only list the number of tickets issued and revenue collected under the “Results” section. According to the posted results, tickets issued for speeding increased from 275,000 in 2007 to 354,000 in 2010, resulting in a jump in revenue from $20 million to $24 million over the same period. (Let’s not pretend that revenue doesn’t matter for traffic enforcement cameras — in June, city officials were upset that not enough people were running red lights.)

If you’ve sped by one of the new mobile units, don’t fret — they’re only mailing warnings this month. But come October 1, any car parked on the side of the road with a few extra boxes on the side or front is likely a speeding ticket waiting to happen.