A few months ago I changed the route I drive to work, taking MacArthur Boulevard instead of Massachusetts Avenue through Northwest D.C. I figured I was saving about four minutes each way--not bad for a 20-minute trip. Then I got a $40 ticket in the mail, with a photo of my car doing 38 in a 25. Busted by a speed cam.

I was peeved, but intrigued. A recent transplant from Northern California, I was familiar with red light cameras but not the speed variety. Now I know more. A Washington Post map last weekend showed 39 "fixed or mobile radar cameras" in the District. In May alone, they generated 58,844 tickets and brought in nearly $3.2 million. Nationwide, jurisdictions in 12 states and the District of Columbia permit police departments to use speed cameras, which are also known as photo radar.

Critics say the cameras evoke Big Brother. They worry that a system that can take a photo of your license plate as you drive through town can also track your general movements. They say cities with cameras are more interested in raising revenue than improving public safety. I say bring on the cameras. D.C. certainly needs the money; collecting small amounts from indisputable minor-league scofflaws seems fair enough. Plus, I appreciate that a computer is deciding who gets the ticket, not a cop who may not like the cut of my fender. As for safety, well, now I don't drive as fast--not on that stretch of MacArthur where those two cameras are positioned on gray poles, and not in other parts of town, either. I don't want another $40 ticket. That's called deterrence.