Dip is advised to keep tilt test
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• British tilt tests for coaches and buses are worth keeping, according to a study commissioned by the Department of Transport.
Guy Tidbury, consultant to Cranfield Impact Centre where the study was conducted, says that parts of the test procedure should be changed but "it is a reasonable method of minimising the occurrence of overturning accidents by maintaining certain standards of design and construction."
Working with David White of the New Zealand Department of Scientific and Industrial Research, Tidbury has developed a computer simulation of PSV rollovers.
The roll stability of any PSV can be determined with this computer simulation, he says, but most of the data used in it comes from the tilt test itself which he recommends as "the most suitable method for determining roll stability."
Tidbury points out that while no other country currently uses a tilt test for PSVs, the USA, Sweden and Australia are all considering introducing one for type approval tests of articulated vehicles.
British tilts limits are 350 for single deckers and 28° for double deckers.
Tidbury recommends that new limits should be intro
duced which vary according to the height of the vehicle's centre of gravity. He also strongly recommends that the current practice of fitting "tilt valves" or keeping selflevelling valves in operation during the tilt test be discontinued as "they would be unlikely to operate in an accident situation."