New hi-tech speed cameras are being installed at a test site in London.
The cameras will be used to enforce a 20mph speed limit
The cameras, which measure a driver's average speed, are being installed on Upper Thames Street between London Bridge and Southwark Bridge.
Four pairs of the digital cameras will start operating on Monday to enforce a 20mph speed limit for 18 months.
Signs will flash to warn drivers before they reach the zone but anyone whose average speed exceeds the 20mph limit will receive an automatic fine.
Tom Duckham, of the London Safety Camera Partnership, said: "Our primary aim is reduce speed-related collisions and to protect vulnerable road users."
Peter Hendy from Transport for London's, said: "In 2003, pedestrians and cyclists accounted for over a quarter of all casualties on London's roads.
"Research proves that a 1mph reduction in average speed results in a reduction of 6% in the number of collisions."
This is the first time these cameras have been used in London and to enforce a 20mph limit.