Campaigners are calling for new legislation to tackle dawdling drivers who they say are a major cause of stress among fellow road users.
The Association of British Drivers (ABD) said people who drive too slow not just irritate other motorists but endanger road safety.
It wants new regulations that will require slow drivers to make way for faster vehicles behind them.
Frustrated drivers caught behind slow-moving vehicles may end up behaving in a rash manner that could lead to accidents or unnecessary van insurance claims.
ABD chairman Brian Gregory said: "If everybody drove at the speed a reasonable person would expect to travel, the roads would be much safer, less stressful places for all.
"Unfortunately there will always be those who wish to travel either dangerously fast or far too slow - causing congestion and prompting rash behaviour."
© Press Association 2011