Claims about the effectiveness of speed cameras have been greatly exaggerated, experts have warned.

The Government estimates that the cameras lead to a 22pc drop in crashes and 100 extra lives are saved per year.

But a doctor from Liverpool University says these figures should be halved.

Speak to the police, camera safety partnerships and community groups in your area.

Also, use Freedom of Information Act powers to see whether crashes at notorious spots have gone up or down over recent years.

Perhaps a recently-installed camera has dramatically reduced the number of incidents at formerly notorious blackspots.