Average speed cameras are to be installed on part of the A13 in east London.
It is the first time such cameras have been introduced on a major urban road in this country.
However once the 84 cameras are installed, the speed limit will be increased on the section from 40mph to 50mph.
Transport for London (TfL), which is installing the cameras, hopes that they will halve the number of people killed or seriously injured along the fast-moving road.
The cameras will monitor average driving speeds on the A13 between Canning Town and the Goresbrook interchange near Dagenham - a stretch where the collision rate has been almost a fifth higher than is typical of major roads in London.
TfL said nearly 500 collisions, including three fatal and 34 serious accidents, were recorded on this stretch of road between 2006 and 2008, with half the collisions being caused by speeding.
RAC Foundation director Professor Stephen Glaister said: "This is exactly the right way to target road safety: take specific action to target a specific problem.
"Average speed cameras are already a familiar feature in roadworks and they have the advantage of smoothing traffic flow rather than creating the stop/start sort of driving often associated with fixed cameras.
"The fact that the speed limit is actually going to be increased is an acknowledgement of this."
© Press Association 2009