In its draft air quality plan, it says "the UK Government has considered potential measures to address exceedances on the strategic road network and has concluded that adjusting speed limits could be practicable."
The Government's air pollution strategy includes ideas which could mean cars that do not comply with the latest Euro 6 emissions standard face charges.
It has also announced a consultation on plans for a "targeted" diesel scrappage scheme and grants to "retrofit" older vehicles to reduce the level of emissions and additional funding for electric taxis.
And following the Volkswagen emissions scandal, under the new Real Driving Emissions regulations, vehicle manufacturers will be required to ensure that real world emissions of Nitrous Oxide (NOx) for new models are increasingly aligned with laboratory testing limits from September 2017. This will improve consumer confidence in manufacturers and deliver real improvements for air quality.
However James Thornton, chief executive of ClientEarth told the Guardian the government was “passing the buck” to local authorities and said he failed to see how the central proposal – clean air zones for urban areas – would be effective without charges to deter the most polluting vehicles.