Average speed cameras on every motorway could save 1.4 million tons of Co2 a year, according to the Sustainable Developments Commission.
Data from the Department for Transport shows that over half of motorway users break the 70mph limit. The Commission claims that the installation of average speed cameras would reduce this.
However, their effectiveness at reducing carbon has been questioned by the campaign group Safe Speed.
The group has previously petitioned Downing Street – securing over 28,000 signatures to scrap speed cameras.
The Highways Agency and road safety partnerships will make the final decision on where and what type of cameras will be installed.