Motorway speed cameras

[griffter]

How do these work then?
If three cars, one in each lane, pass the camera at the same time, and one car is speeding, is the offender automatically detected?
Or must a 'three lane' camera photograph be manually checked?
What if more than one car is speeding?

[marcp68]

Usually there's a camera for each lane I believe.

[griffter]

Sorry, I didn't mean the gantry type, but rather the 'box on a stick type' (which I've only ever seen singly) used e.g. in roadworks.

[GlenMH]

A human operator will need to look at the photos and use the marks on the road to decide who was going the speed that tripped the camera.

Glen

[ledfoot]

If you are talking about the 'Speedcurb' cameras, they use sensors buried in the road surface.

SpeedCurb™ - Speed Violation Enforcement System

The speed of vehicles passing through a monitored section of carriageway is measured by Piezo sensors buried in the road surface, or for overseas versions our system can be adapted to use other detection methods. The RedSpeed program continuously monitors each of the speed sensor interfaces. As soon as a timing reading is received from the timing processor, it is checked for accuracy, sequence number and validity and converted to a speed using the stored sensor spacing. If the measured speed exceeds the programmed speed threshold, then the vehicle presence loop is monitored until the vehicle clears the loop. The detective loops also trigger the enforcement system to take three images of the offending vehicle.

www.redspeed-int.com/en/products_redspeed.htm#2

[deeps]

GlenMH said:

A human operator will need to look at the photos and use the marks on the road to decide who was going the speed that tripped the camera. Glen

Which isn't always accurate when the first vehicle's doing say 44 in a 40 and the other's doing 47, and the first vehicle obscures the others number plate, so operator sends NIP to first vehicle.