Ministers are considering plans to increase the speed limit on the UK's motorways from 70mph to 80mph.
The current limit of 70mph is out of date and a higher one would bring economic benefits, according to Transport Secretary Philip Hammond.
The new plans would be implemented in 2013, but before that a consultation process is due to be launched later this year.
RAC Foundation director Professor Stephen Glaister said: "There are good reasons for making 80 the new 70, and good reasons not to. Drivers travelling that 10mph quicker might reach their destination sooner, but will use about 20% more fuel and emit 20% more CO2.
"There is also likely to be a slight increase in road casualties."
If the new plans come into place, drivers will want to select the most comprehensivecar insurance cover available in the market in view of a higher accident risk.
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