Up to a third of motorway capacity is being wasted by drivers' poor lane discipline, according to research by the RAC Foundation.
Too much braking is causing phantom traffic jams, says the RAC
"Selfish" middle-lane hoggers and outside-lane blockers are the worst culprits, said RAC head Edmund King.
"If we can encourage these drivers to practise better lane discipline it would be equivalent to adding 700 miles of new motorway capacity," he added.
Police have the power to pull drivers over for bad lane discipline.
They can even prosecute lane-hoggers in certain circumstances.
But a reduction in traffic police means many atrocious drivers get away with their behaviour, the RAC said.
It said traffic jams were being caused by too much "red-light braking".
TOP 5 BAD MOTORWAY HABITS
Tailgaters: over 40% of drivers are guilty of tailgating, which limits motorists' ability to react to events ahead
Middle-lane hoggers: a major cause of road-rage on motorways
Failing to indicate: considered a nuisance and a danger to other drivers
Swoopers: who cut across lanes with little regard for other
Chatterboxes: people who talk on hand-held mobile phones while driving, which is banned
A car changing lanes or exiting the motorway sometimes leads tailgating motorists to brake.
This can lead other cars behind to brake hard until they all eventually come to a standstill.
"Poor lane discipline wastes the scarce resource of road capacity,
encourages road rage and leads to dangerous tailgating,"
Mr King said.
"We would like to see more traffic police on motorways pulling drivers over
for hogging the middle lane."
He said perhaps "courtesy cops" who advised drivers how to use the lanes on the new dual
carriageways and motorways in the late fifties and early sixties should be re-introduced.
The study of 15,000 motorists in July was carried out by the RAC as part of National Motorway Month.