an interview survey of 497 drivers of high vehicles was conducted in 1978. lorry drivers' knowledge of the overall height of the vehicle plus any load being carried at the time was compared with actual height measurements. although95 per cent of drivers interviewed claimed to know the height of their vehicle, only 185 drivers were accurate to within 3 in either side of the correct height and 73 were underestimating their vehicles' height by more than 3 in. lorry drivers' knowledge of road signs relating to low bridges was also investigated. seventy-two per cent of lorry drivers were fully or acceptably correct in their understanding of the road sign 'headroom at hazard ahead', but only 31 per cent were correct in their understanding of the road sign 'available width of headroom at hazard'. drivers were asked what they did when they had to cope with low bridges and some details of accidents involving low bridges were recorded. in addition drivers' opinions were obtained about a number of suggested ways of reducing the incidence of low bridge strikes by lorries. an infra-red detector system which indicates when a vehicle exceeds the signed height was the most favoured among the lorry drivers.sixty-eight per cent of the drivers interviewed thought that this system would work best. other methods such as gongs across the road, lanes marked under bridges, words painted on the road and rumble areas were all considerably less popular.(a)

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