Speed limiters should be fitted to cars and lorries on a voluntary basis to reduce carbon emissions and cut accidents, a report by the Commission for Integrated Transport and the Motorists' Forum has recommended.
The innovation - using satellite navigation technology to read the road's speed limit and adjust the vehicle's accelerator – has been given a cautious welcome by the DfT.
The Intelligent Speed Adaptation (ISA) system has been tested in the UK over 355,000 miles of driving on roads where the speed limit was known.
Using the system on urban roads with a 30mph limit could increase fuel consumption and emissions, because cars operate more efficiently above that speed, the study acknowledges. But there should be significant reductions on roads where the limit is 70mph.
The report suggests government vehicle fleets should be equipped first of all to encourage other drivers to join the scheme, and proposes that it should be provided for newly qualified drivers and those convicted of dangerous driving.
The DfT said: "Our view [is] that it could be a useful road safety feature for drivers who wish to use it."