"On the speed/safety issue, if the intention was to slow down vehicles
at accident blackspots, this could be done with traffic lights linked to
speed detectors, as in Spain.

If you exceed the posted speed, the lights turn to red and you have to stop. After you have experienced a few of these and endured the hostile glares from other drivers, you soon learn to comply with the speed limits.

There is no revenue generated by this system, so although it is 100%
effective at speed reduction, it will never be adopted in this country. This
proves cameras are not genuine safety devices, but cash-generation machines, reinforcing the view of seven in eight drivers quoted in the article."