Red light cameras and cyclists

[hornet]

Can a bicycle trigger a red light camera? Ask this as I saw a cyclist go through a camera enforced red light last night but the camera didn't flash.

[streaky]

Don't be silly! Cyclists are exempt from obeying any traffic signals ... by virtue of their owners being untraceable, so cannot additionally contribute to filling Gordon Brown's financial "black-hole" - Streaky

[hornet]

streaky said:

Don't be silly! Cyclists are exempt from obeying any traffic signals ... by virtue of their owners being untraceable, so cannot additionally contribute to filling Gordon Brown's financial "black-hole" - Streaky

I know that....just pondering that if a bicycle should set off a red light camera but didn't, was the camera live?

[zumbruk]

Unlikely that a cyclist has a large enough radar cross-section to set off a red light camera. And even if they did, with no plates, how would anyone identify them?

[gh0st]

Usually RL cameras are piezo based not radar based but there is probably not enough metal or wieght to trigger it.

[te51cle]

My mountain bike has enough good old fashioned iron in it to trigger the standard chevron shaped inductive loops that precede most traffic lights. Piezo triggers are usually more sensitive than other systems so I would expect it to be able to trigger a camera whichever system it was using too.

Of course if there's just an empty box then I wouldn't expect anything to happen !

[pdV6]

te51cle said:

My mountain bike has enough good old fashioned iron in it...

Not many of them left in use any more!

[streaky]

anonymous said:

[redacted]

I don't believe that weight per se or {SI has anything to do with triggering red-light cameras - Streaky

[echo]

most RL cameras use inductive loops in the road. they would not normally be triggerd by a push-bike.

[Tafia]

anonymous said:

[redacted]

I think you will find that weight is not a factor in triggering these devices.

They work with a wire loop buried in the road. A current is passed through this loop. When a lump of steel enters the magnetic field surrounding the buried cable, the change in inductance is detected and the monitoring device then "knows" a vehicle is present.

For a pretty picture of this in action, peep at

www.howstuffworks.com/red-light-camera2.htm

[echo]

te51cle said:

My mountain bike has enough good old fashioned iron in it to trigger the standard chevron shaped inductive loops that precede most traffic lights. Piezo triggers are usually more sensitive than other systems so I would expect it to be able to trigger a camera whichever system it was using too. Of course if there's just an empty box then I wouldn't expect anything to happen !

The angled loops for the traffic lights will sometimes detect a pushbike - the most sensitive part is the short edge (ie the bit parallell to the direction of travel) but these are just counting activations - the red light camera tries to detect speed so needs a bigger signal.