Carbon Emissions: Motorways Question Asked by Lord Hunt of Chesterton To ask Her Majesty's Government whether they will promote the contribution of moderating driving speeds on motorways to reducing carbon emissions. [HL728] The Secretary of State for Transport (Lord Adonis) The current national speed limit of 70 miles per hour on motorways reflects a balance between economic, environmental and safety objectives, but we keep this under review. Enforcement of speed limits is a matter for the police. The THINK! campaign is aimed at achieving better compliance with road safety law overall, including speed limits. The Act on CO2 campaign encourages smarter driving, including staying at or below the speed limit to reduce emissions.