Lights on thousands of miles of A-roads in England could be dimmed in a bid to save money and reduce carbon emissions.
The Highways Agency is proposing to reduce light levels on major roads when traffic levels are "very low".
Norman Baker, the local transport minister, supported the move as long as safety was not compromised.
In a parliamentary written answer he said: "The level of light reduction will be based upon internationally agreed standards and made in consultation with the UK's Institute of Lighting Professionals.
"It is right that lighting authorities consider, in the interests of cost-saving and the environment, whether lighting can be sensibly dimmed or turned off, consistent with proper safety assessments."
A spokesman from the Highways Agency said: "This is not about switching off lights on A-Roads. However, we want to continue to reduce the carbon footprint associated with managing England's major A-roads and one of the ways we are considering doing this is dimming lights when traffic levels are very low.
"Any changes to light level will be determined in consultation with industry experts and will meet internationally agreed standards to ensure there will be no impact on safety for road users."
Research into when and where the lights could be dimmed will be conducted in the next financial year.