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Pownall Case Studies

Bus Roll Away Accident Prevention - National Express


Determined to prevent bus roll away accidents National Express Group have implemented a programme to install Pownall voice alert systems that warn drivers should they attempt to exit the bus without the handbrake being applied.

Initial trial units were fitted to buses operating in the Birmingham area. Once the warning is activated the park brake must be applied to silence the alarm message.

Garage staff had concerns that they would be driven to distraction having to listen to repeated warning messages telling them to apply the park brake while carrying out brake maintenance.

However, Pownall promptly produced temporary overrides specifically for use during maintenance and service related work.


Following an internal safety review Tardis Environmental have installed Pownall safety brake locks to their fleet of environmental tankers. Driver operators wear safety harnesses secured to the vehicle whilst emptying cesspits. As the vehicle engines have to be running to power on board pumps, Tardis Environmental identified a risk that a thief could jump in and drive away with the driver fastened to the rear of the vehicle by their safety fall harness.

With the Pownall safety brake lock activated anyone attempting to drive away finds the vehicle brakes locked on and at the same time an audible alarm sounds. 


Quarry Dumper Rollaway Fatality



A dumper being repaired following an electrical breakdown rolled with fatal consequences. Apparently, the park brake was not applied. To test the repair the engine was started and left running while final work was being completed. As brake system air pressure built up with the park brake not applied the spring brake actuator released and the dumper rolled with fatal consequences. In our opinion there were three contributing factors in this incident, loss of electrical power, driver error, and loss of brake system air.


Following enquires from the group tasked by the HSE to find a solution to help prevent similar incidents in the future. Pownall proposed two products, firstly the Sentinel Duo electro pneumatic park brake not applied alarm, which warns drivers if they attempt to exit the vehicle without having first applied the park brake, additionally it warns if the park brake is unapplied with electrical power isolated.
In this particular incident the warning would have activated as soon as the electrical power loss occurred and continue the warning until the park brake had been applied or system air depleted at which point the spring brake actuator applies the brake (see below).

The second proposal being the Pownall Sentinel low air cut off valve. This valve is mounted in the cab and shuts off the air supply to the park brake control valve and thus spring brake actuators when supply air pressure to the park brake control valve drops below a set point. Once tripped, the valve is manually reset by the driver once system air pressure is restored. The low air trip point is critical in order to ensure that maximum possible spring park brake efficiency is maintained.

The low air cut off valve is available as a kit for Volvo customers direct from Volvo Construction equipment. In addition it is a mandatory requirement for all plant with air spring brakes on all Scottish Coal Sites.

Mobile Library & Exhibition Unit Rollaway



A local authority safety risk assessment highlighted the potential risk of a playing child releasing the park brake on mobile library’s and requested the body builder, to fit a device to prevent a possible occurrence.


A Pownall Ultra air brake locking valve, fitted with an air horn tamper alert that sounds should the park brake control valve be released while the vehicle parked.

Dumper Raised Body Collisions



Tarmac had experienced damage and driver injuries caused by collision with overhead constructions and objects such as conveyors and electricity supplies caused by dumper drivers forgetting the body is raised and driving off despite having standard height warning devices fitted.


Pownall proposed, then manufactured a body raised interlock system to address the problem. The system locks the vehicles brakes while the body is raised but does not interfere with normal operation allowing deliberate movement but preventing the driver from just driving off with the body raised.
An additional benefit is the reduced risk of tip over’s.
Articulated dumpers are known to tip over when driven on uneven rough ground with the body raised due to the now high centre of gravity.

Pownall Security Systems Ltd

Tecnair Group

6 Station Road



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