A new kind of digital speed camera is being installed in a road tunnel in east London.
Fines from speed cameras are used to pay for more cameras
The new digital camera, which does not require servicing, is being tested at Limehouse and should be fully operational next month.
Surveys have shown that nearly all the drivers who use the tunnel break the 30mph speed limit.
In the last three years, 14 accidents there have led to death or serious injury.
Roger Vincent, of the Royal Society for the Prevention of Accidents (RoSPA), told BBC Breakfast the camera would save lives.
"Each one of us knows what the speed limit is and if we exceed it we have less time to react if something goes wrong," he said.
"We need to educate people that many times they need to drive well below the limit at speeds appropriate to the conditions."
With traditional cameras, using film which can run out, motorists hope they can get away with speeding.
But the new digital version sends images along a phone line to a Metropolitan Police centre in Kent.
And fines can be sent out within 24 hours.
Edmund King, from the motoring organisation RAC, said it was important not to over emphasize the danger of speed.
"There are many other causes of accidents," he told BBC Breakfast.
Access to Docklands
"One problem is with the increase in speed cameras there's been a decrease in traffic police.
"A camera can't pick up the drunk-driver or the tail-gater. We must target the cameras where they're really needed and then the motorist will react to them because they'll know it is a problem area. "
The 1.8 kilometre Limehouse Link tunnel, which opened in 1993, is a dual carriageway providing access from the City to the Docklands redevelopment
It carries 80,000 vehicles a day.