Average speed cameras are being trialled by Transport for London on the A13 between Canning Town and the Goresbrook Interchange in east London.
This will be the first place in the country where average speed cameras can enforce the limit on a road with multiple entrance and exit points.
Nearly 500 collisions, including three fatal and 34 serious accidents, were recorded on the stretch of road between 2006 and 2008. Half those collisions were caused by speeding.
A total of 84 cameras, based at 37 locations, will monitor the speed of vehicles.
The system will be fully operational by this summer.
While the camera system is being installed and tested, signs will be placed along the A13 informing drivers that the average speed camera system is not currently enforcing.
However, the existing GATSO speed cameras along the stretch of road will continue to enforce the speed limit until the new system goes live.