For many years, passenger service vehicles (PSVs) have been fitted with rubber bellows (also known as airbags) supplied with air from the vehicle's air compressor. These allow the height to be varied to suit certain needs, for example lowering the step for improved access.
Vehicle ground clearance can suddenly and unexpectedly change due to a drop in air pressure. This presents crushing and trapping hazards to technicians recovering or repairing vehicles, especially if working beneath them.
In addition, recovery of casualty PSVs can be made more difficult because of reduced ground clearance. Comprehensive guidance is available in the free HSE publication PM 85 Safe recovery (and repair) of buses and coaches fitted with air suspension
