Trrl Lr 788

Nine high laden articulated vehicle combinations from 32 tonnes (Mg) to 45 tonnes (Mg) gross train weight were driven into a roll over condition on different manouvres to assess their stability in roll and the effect of different vehicle characteristics. The vehicles were also titled sideways on a platform to the point of balance. Roll over occured at lateral accelerations from about 0.2g. Trailer roll was the governing factor in the overturning of the combinations tested. Increased spring stiffness spring base width and coupling stiffness increased the trailer roll resistance. Measurements demonstrated that the tilt method gave a good indication of roll stability. Calculated results from a computer program of lateral acceleration required for roll over differed from the dynamic results by 10 to 40 per cent. Roll over occurs in 3-4 per cent of heavy goods vehicle injury accidents. Reasons for this are considered to be geometric layout, lack of driver awareness of the total roll of an articulated combination and a tendency for a rigid vehicle to become self stabilising due to loss of drive in roll. Multiple turn manouvres did not increase the risk of roll over. A roll over warning device could be useful