Those sprays and shields marketed as red-light-camera blockers? They don't work, according to a recent study that cited Los Angeles Police Department data.

The LAPD tested both Photoblocker, which is sprayed on to a plate, and a convex license plate cover marketed as a red-light-camera buster. Each potential foil was run 160 times through red lights with cameras, both in day and night conditions. The results were analyzed by researchers who published a report in the Institute of Transportation Engineers Journal.

The verdict? Despite L.A.'s 32 red-light-camera intersections, which dole out $500 tickets at almost McDonald's drive-through-like speed, the study concludes that you'd be wasting your money by relying on these devices to stop a traffic ticket. In fact, the plastic-like plate shield actually increased clarity for the red-light cameras in some conditions, according to the study.

“The countermeasures had no effect on plate legibility under dark conditions, with the exception of V-2 (license plate shield), which occasionally caused a slight increase in front-plate legibility in half of the images,” the study's authors state. “All rear plate images were clearly legible, with no significant difference between the test plate images and the control plate image. A citation could have been issued in all cases.”

Morning glare, however, did have an effect on the cameras' abilities to capture plate numbers with the plastic-like shield. The golden hour? Eight to 9 a.m.

In 2007 a Discovery Channel MythBusters show came to similar conclusions. Besides, the devices are illegal in California anyway (though we're not sure how the spray would be discovered).

LA Weekly