The thing about urban myths is that they can never be proved or disproved.

But in what is a rare case of alleged evidence surfacing, Devon and Cornwall Police are reported to be investigating the existence of Motorway Snooker.

The rules are simple. Motorway traffic police stop speeding cars, scoring as if the cars were snooker balls. So stopping a red Fiesta would score one point, a black BMW would score seven, followed by another red, and so on until all the colours have been done. Highest break wins.

A typical sight on motorways

Broadcaster Victor Lewis-Smith has identified a variation on the rules. He says instead of scoring the appropriate score for the car's colour, the officers score the number of points the driver's licence will be endorsed by.

Although the Devon and Cornwall force has denied any wrongdoing by its officers, it is investigating a complaint from publisher John Emslie, who was stopped speeding in a yellow Alfa Romeo Spider on the M5.

Mr Emslie told The Times that when he asked why his partner, who was driving a black Jeep Cherokee behind him at the same speed, had not been stopped, he said he was told a game of Motorway Snooker was in progress.

For the police's part, Superintendent Stephen Swani said anyone speeding should expect to be caught and prosecuted. "If people are stopped for speeding, it's because they speeding, not because of the colour of their car," he said.

Red cars more likely to get stopped

But Mr Emslie is not alone. An MG owners' club magazine reported last year suspicions of the game taking place when, on having changed his car to a red model, one chap found himself being stopped every other day.

And thieves have got in on the game as well. Police in Humberside, as well as other places in the UK, have in the past issued warnings to owners of cars of a particular colour, knowing where the thieves have got to in their "break".

Whether or not the game exists, there are certain tips you can apply to avoid getting caught.

• 1) Don't drive red cars - because there are 15 reds on a snooker table, the reds are much more likely to get potted.

• 2) Similarly, don't drive black cars. Although they may look sleek, stylish, moody and expensive, earning seven points makes them the top target.

• 3) It's probably not a good idea to drive pink cars either. Not only are they high scorers, but the chances of looking sleek, stylish, moody or expensive are slim.

• 4) If you don't have a red car, you should still be wary. Driving behind them could make you liable for a swift one-two, with you both being "potted" in swift succession.

• 5) Mr Emslie was driving a yellow Alfa, but in the rules of the game, yellow, green and brown should be fairly safe bets, as they are low scoring. Getting a bad position after a red might give a playing officer no choice, though.

• 6) White cars are safest of all. Police cars, being white, act as the cue ball in the game. So if a white car is booked, it is tantamount to a foul and will count as four points away. Jason Copeland of the MGM group said, in contrast to the driver with the red car, he had been driving a white car for seven years without being stopped.

Twice as likely to kill at 35mph than at 30, the government warns

Simplest of all, and surely the advice straight-faced coppers would give, is don't speed and you won't be caught.

The Department of Environment, Transport and the Regions has been running a hard-hitting campaign to tell drivers that cutting their speed to 30mph from 35mph halves the risk of killing pedestrians.