Devon's street lights could be dimmed or even turned off to help tackle climate change.
Street lights cost the county council £2.5m a year
The county has 70,000 street lamps and 12,000 illuminated traffic signs.
But the county council says the lights account for nearly 40% of its carbon dioxide emissions and cost £2.5m, a sum it wants to reduce.
The authority said any decision about turning the lights down or off would be made after considering any adverse effects on safety.
Light pollution in rural areas rose by 27% between 1993 and 2000
David Whitton, head of transport services, said: "Where road safety and crime and disorder is not a problem we need to examine very closely whether or not we need to retain lighting.
"We could also consider a lighting solution for only part of the night, which would also save us energy."
The Council for the Protection of Rural England and astronomers have been trying to combat what they call "light blight".
Satellite maps of England show that severe light pollution increased by almost a fifth between 1993 and 2000.
In the rural areas where dark skies are still a possibility, there was a 27% increase.