A small electronic message unit, powered by wires which plug into a car's cigarette lighter, could help diffuse "road rage" experienced by over excitable motorists and also make a tidy return on investment for its inventor, computer consultant Robbie Crawford. The ghizmo, manufactured in Scotland and developed with financial assistance from the Bank of Scotland, went on sale in Britain this week, retailing at £50 sterling. Crawford expects to sell a million units in the UK this year, estimating that the motorists' peacemaker has the potential for around 20 million global sales in five years. The device, attached to the back window of a car, can flash up pre-programmed messages in red lettering such as "sorry", "thanks" or "help" at the touch of a button. It is tamper-proof, so renegade drivers cannot key in offensive remarks. In bringing such an innovative business idea to fruition Crawford naturally hopes that sales will take off, enabling him to flash the message "Thanks a million".