DRIVING, like love, means never having to say you're sorry, in most motorists' logbooks. However, macho motor man is to be offered the chance to turn over a new leaf.

An electronic device which fits into the rear window of any car and displays the words ''Sorry'' or ''Thank you'' at the touch of a button will be launched today to coincide with National Courtesy Day on the roads, organised by the RAC and the Courtesy Campaign.

The device has been developed by Edinburgh-based Urbane Systems. The company's managing director, Robbie Crawford, came up with the idea for the device called Envoy after he found he was acting like a ''devil'' on the roads.

He said: ''I was one of the worst, and found that I was cutting people up and apologising with hand signals which could easily be misconstrued, so I thought this would be a good idea.

''I made a prototype of the device, tried it out myself and found it really useful. One time I was driving a BMW and overtook a van full of workmen. One of them stuck his finger up at me for overtaking, but when I flashed up 'Thanks' they all starting clapping and waving, so it totally defused the situation. It's very easy to use and the message lights up in red bulbs, so it's easy to read from a distance.''

Courtesy Campaign founder, the Rev Ian Gregory, said: ''We have advocated for years that this kind of device would help drivers communicate with each other in a humane way. Now a firm has come up with the necessary technology, we can only commend the idea.''

Any driver can fit Envoy, which is 10 inches long by three inches high and costs #49.99, on to the base of their rear window. Wires from the device run to the car's cigarette lighter and from there are attached to a piece of Velcro with three buttons which can be stuck near the dashboard.

A blue button is for ''Sorry'' and a green one for ''Thanks''. There is also a red button which flashes up ''Help'' for drivers in difficulties.

The device is also tamper-proof to stop motorists programming in their own rude messages which provoke road rage rather than combat it. ''It's impossible to change the message, so there's no danger of people doing that,'' said Mr Crawford.

Sue Nicolson, of the RAC, said: ''We have checked this product out and think it could be useful to defuse potential road rage situations.'' She added that today's National Courtesy Day was an attempt to drive home the message to anti-social drivers that good manners cost nothing.

The RAC is teaming up with the Scottish Office and the Highways Agency, which will be flashing up electronic roadside messages on motorways and trunk roads.

Messages will urge the UK's 24 million drivers to keep their distance and avoid hogging the middle lane in an effort to encourage consideration rather than confrontation.

The move follows the release of the RAC's annual survey of bad driving habits which shows that motorists who chat on mobile phones are the number one cause of road rage.

Mobile phone users who hold their handset rather than investing in a hands-free kit came top of the list of drivers' bugbears - followed very closely by ''tailgaters''.