A new type of digital speed camera will be switched on at a busy road tunnel in east London on Thursday.
Mobile speed cameras will help tackle road deaths
Six of the cameras, which can log the speed of two cars simultaneously and can send images down a phone line, have been installed in the Limehouse Link.
Surveys by road safety campaigners found 50,000 of the 80,000 drivers using the tunnel each day ignore the 30mph speed limit.
In the last three years 18 people have been killed or seriously injured there and another 63 have suffered minor injuries.
Regular speed cameras can not be used because the 1.8 kilometre tunnel, which links the City to Docklands, would have to be closed at regular intervals to take out the film.
The new cameras do not need servicing, do not run out of film, and can send out fines within 24 hours.
The digital images can be encrypted and sent to a Metropolitan Police centre in Kent.
The London Safety Camera Partnership says the cameras are being introduced to "reduce casualties, not to increase offences".
They say since cameras were installed in July, drivers have begun to slow down.
Edmund King, from the motoring organisation RAC said speed was not the only cause of accidents and cameras did not pick up drunk drivers or tail-gaters.
But Bob Gayle, whose son was killed in a crash 4 years ago, said speeding was one of the "crucial factors" determining whether crash victims lived or died.
He told BBC London: "I hear these stories about it being a way for the police to raise income and so on and it is absolute nonsense.
"This is a way of improving road safety for all of us. Each one of us is responsible for other people on the road as well."