UK motorway speed limits could be raised to 80mph and those on city and town roads be reduced, with the decision on restrictions being made as much on cost grounds as on safety.
Transport Secretary Philip Hammond said yesterday that decisive factors could include the economic benefits of faster travel as well as environmental concerns.
Britain's 70mph motorway speed limit has been in force since 1965 — when it represented the top speed of most cars on the roads at the time.
Mr Hammond said: “We need to do this on a pretty rigorous cost-benefit analysis basis.
“At the moment there are a clear set of criteria for making these decisions. Perhaps we ought to ask if we are using the right set of criteria.”
He suggested that in some towns speed limits could be reduced from 30mph to 20mph, on both environmental and safety grounds.
The Transport Secretary's comments came as a report from the RAC Foundation found that the number of traffic lights in the UK had risen by 30% between 2000 and 2008, with the number in London increasing by 23% to more than 6,000.