On a strech of road near to where I live, two cameras have been changed to face the opposite direction. This means that the cameras are facing the opposite direction to the white grid lines painted on the road. Does this mean that both cameras have been decommissioned?
The standard Gatso, yellow box ones take it as you go away from them. There are some time distance ones on the motorways that read the front plate though, so good news for motorbikes!
Gatso cameras take 2 fotos of the vehicle half a second apart. The lines on the road are used to calculate how far the vehicle has travelled between the 2 fotos. From this it can be calculated how far the vehicle has travelled in terms of feet per second and ulitimately in miles per hour.
The Truvelos operate entirely differently they measure your speed by calculating the time taken to pass between detectors in the road. So you wont see any markings necessarily.
I dont think you can assume that they are not working simply because they are now pointing the other way. If they are GATSOs then they cannot be used without markings on the road. It may be that they have actually been replaced by Truvelo or something similar