This idea is a way for the police to identify how fast a
vehicle is driving on a highway, *and* who is driving it,
using only a trio of cameras.
All three cameras are mounted above the highway, aimed
downward. They are mounted either on the frames
holding exit signs, or on the undersides
of overpasses. A
special purpose framework might also work, but would
obviously be pricier than reusing existing structures.
The first camera is angled so it can see cars coming
towards it, specifically so it can look through the front
windshields at the drivers. The second camera is mounted
fairly close to the first one, but aimed so it can see the
backsides of these same vehicles -- especially their rear
license plates. The third camera is mounted hundreds of
feet further along this same highway, also aimed
downwards to see rear license plates of vehicles passing
under it.
By dividing the distance between the second camera and
the third one by the time it takes for each vehicle to be
seen by the second camera and the third, we have each
car's speed.
The reason a photo of the driver is needed is so speeders
can't say, "Sure, you saw my car speeding, but I wasn't in
it!"
For legal reasons, it can't be 100% automated, but the
amount of effort needed for a law officer to look at the
pictures and times, and say "yeah, that's the same car in all
three shots, *and* the person driving matches the photo of
the drivers liscence of the person registered as the car's
owner" then print out a ticket to mail to you, is pretty
small.
An alternative method of delivering tickets to speeders is
for the system to transmit, in real time, the pictures and
calculated speeds, to a nearby police car, which chases
down the speeding car, and issues a ticket.