Speed and toll cameras?.....

[RegSpec]

How do they work?
How do they tell the difference between a car and truck or a vehicle with multiple axles?.....
I know they have height sensors to apply the higher toll to trucks but Ive always been curious about the multiple axle difference?...

[cobramania]

In NSW, toll cameras & fixed speed cameras have multiple electronic sensors in the road surface (same as Traffic Lights). They are spaced specific distances apart & as you go over them, the timing between each sensor triggering, lets them know how many axles a vehicle has & how fast you are traveling (fixed speed cameras in NSW don't use radar anymore, they now trigger from electronic sensors in the road surface, almost impossible to fool, less chance of errors in readings & can also tell which lane a speeding vehicle is in, even if there's vehicles traveling along side each other).

The distance between axles only varies a minor amount for each vehicle type, & the space between axles is much greater & easily defined between a car, car with trailer, light truck (pantec), bus, semi-trailer, B-double, etc.

The heavy vehicle cameras, take video evidence, & a computer looks at the footage & using mathematical calculations, can seek out & find the vehicle dimensions much the same as face recognition on your still or video camera.