May 17, 2012 18:39 BST New research from Green Flag shows that 4.6 million (13 per cent) motorists have been driving on empty in the last three months. Green Flag has termed these drivers ‘Vapour trailers,’ motorists that risk running out of fuel by regularly driving with the petrol warning light flashing. In the past 12 months, a staggering 1.4 million (4 per cent) motorists have run out of fuel whilst on the road.