Smarter Driver: What you need to know about speed cameras
The simplest kind of speed camera is basically a radar gun on a stick, but those are easy for the speeder to beat.
Slow down for a few hundred yards and then Speed up again.
So the new trend in US speed cameras may soon be corridor averaging with ALPR cameras.
Those are automatic license plate recognition.
Now if you're one of our UK viewers, none of this is new to you, having debuted back in Scotland in 2004.
Here's how corridor averaging and ALPR is used.
A camera recognizes your car's license plate at one point on the road.
As you drive down the road further, additional cameras recognize your plate again and again and record it each time with a time stamp.
Since the distance between those cameras and the times at which they spotted you is known, A little simple math results in an average speed and potentially a ticket.
[NOISE] One of the first major US tests of corridor averaging with ALPR was in Montgomery County Maryland, which added the tech to its standard speed cameras in 2012.
The Insurance Institute for Highway Safety has since used it as a study base and just released a few numbers.
They estimate these cameras generated about 30% decrease in fatalities and serious injuries.
That would mean 21,000 fewer deaths and serious injuries if this was used nationwide.
And that in Montgomery County, fatalities and serious injuries fell 27% even on nearby roads where these cameras weren't specifically being used.
A spillover effect.
Because I know you're wondering, Montgomery County posts the location of all of its speed cameras on a county web page.
They're moved regularly, and you can be sure that drivers share those locations on crowdsourced nav apps like Waze.
And there is, of course, a vigorous debate as to whether some municipalities Sneakily deploy traffic cams to generate more revenue than speed reductions.
And in some states, notably California, this corridor averaging license plate camera technology is expressly prohibited as a speed trap.
For now at least.
It pays to double check what kind of speed cameras are in use where you travel.
And not give them a reason to notice you at all.
More car tech demystified right now at CNETOnCars.com.
Click on Car Tech 101.