Overview: Motor manufacturers spend millions of pounds on research and development and part of that money goes on the practical road testing of vehicles. William Woollard looks at Britain's longest test track to find out if the expense and effort is justified. Jackie Stewart looks ahead to the new law to make the wearing of seat belts compulsory. If you thought it was difficult enough to take your driving test, Sue Baker finds out how the professionals do it at the Army School of Mechanical Transport.