Farmers in Cornwall will be able to use red diesel when helping to clear winter roads without fear of recrimination.
Agricultural vehicles play a vital role in gritting rural areas and farmers have previously been concerned at possible repercussions from Her Majesty's Revenue and Customs (HMRC).
But now HMRC has announced a relaxation in the rules governing the use of red diesel following a national consultation with local councils.
The National Farmers' Union (NFU) welcomed the news and said it would enable more farmers to assist local communities during bad weather conditions.
It said tractors and other approved farm vehicles would now be able to use red diesel to help provide access to schools, hospitals, remote dwellings or local communities cut off by ice and snow.
Previously, only purpose-built gritters were permitted to use red diesel to clear roads. Although in recent years Her Majesty's Revenue & Customs (HMRC) has temporarily relaxed the rules in extreme weather, prior to that farmers would have risked prosecution if caught.
The rule change will specifically allow the use of red diesel in any vehicle classified as an 'agricultural machine' for gritting 'as and when conditions demand it'.
NFU transport spokesman John Collen said: "This is an issue the NFU has been pursuing for a number of years and HMRC has shown that it understands the issues facing rural communities in times of extreme weather.
"We are pleased that the proposed amendments will extend to all vehicles registered in the agricultural tax class, which includes agricultural quad bikes, and that there will be no limit on distance."
HMRC will now draft an amendment to the legislation for ministerial approval and will publicise when the changes come into effect.