Inflatable rubber policeman gives drivers the hump

Motorists in the City of London are testing out a new traffic hump – the Dunlop Transcalm – which could soon be used to slow traffic throughout the UK.

The new humps have been installed for road-trials on the Puddle Dock public street, close to Blackfriars station.

Developed by Dunlop GRG and highway consultants Pell Frischmann and the system’s inventor Graham Heeks, the Transcalm has been carefully designed to overcome the disadvantages of conventional road humps.

Conventional asphalt or concrete traffic humps can cause neck injuries, punish emergency service vehicles as much as speeding motorists and disrupt public transport. They also raise environmental concerns about the amount of noise and pollution they cause which often leads to them being removed.

Even at low speeds, static traffic humps can damage vehicles, aggravate neck and back injuries and disrupt public transport.

The Dunlop Transcalm is an inflatable rubber unit incorporating a unique Norgren air valve that controls the rate at which air escapes from the hump when trafficked.

As vehicles drive over the Transcalm at the designated speed, the system deflates, thus minimising disruption. At higher speeds the valve closes and the motorist encounters a rigid deterrent with similar restraining properties as conventional road humps.

The Transcalm can not only be set to close at a predetermined speed – between 5 and 30 mph – but also incorporates a facility which allows the units to deflate when trafficked by large emergency fire vehicles when travelling at speed, leaving the road virtually unhindered.

Mike Armstead, Chairman of Dunlop Transcalm said, ‘The concept was based on the basic premise that responsible drivers should not be punished for travelling within the speed limits. ‘The Transcalm has been on the drawing board for a number of years and is designed to overcome the many disadvantages associated with traditional traffic calming methods. We now await consumer response with interest and excitement.’

Transcalm’s manufacturers hope the design will have global appeal with all those wishing to regulate road traffic speeds and see widespread application on many types of public and private roads.

Despite the negative associations, static traffic humps or ‘sleeping policemen’ have proved effective in modifying driver speeds and reducing accidents. Department of Transport statistics show that minor reductions in speed decrease both the severity and number of accidents.

A short history of humps

Traffic humps have been in existence in the UK since the early 70s, but following criticism of the jarring nature of the speed deterrents the nineties saw a number of alternatives developed. There are currently around 50,000 traffic humps on British roads today.The round-top hump

Perhaps the most familiar in the hump family. The round-top was developed in the Netherlands and landed on British roads in the early seventies. Still the most common, the round-top hump is between 25mm and 100mm high and up to 3.7m long.

The flat-topped hump

This squarer version became fashionable in 1990 when traffic humps became regulated by the Highways (Road Humps) Regulations Act. Between 25mm and 100mm high and a minimum length of 2.5 m. The optimum angle of tapered sides is a gradient of 1 in 4.

The sinusoidal hump

An attempt at easing the discomfort of the round-top by making the gradient between the base and apex less harsh.


Hard, triangular, thermoplastic strips approximately 37mm high and 900mm wide.

Speed cushions

Originating in Germany, these rectangular humps are laid across roads in twos or threes. Wide enough to slow cars but not buses and emergency vehicles. 100mm high.

Rumble strips

Not really a traffic calming measure, more a warning to drivers of something ahead.


single lane sections and road markings represent a more recent attempt to slow down speeding motorists and modify the original traffic hump into a more comfortable disruption:

Dunlop Transcalm

Currently being road tested at Puddledock service road, Blackfriars, by the Corporation of London. An inflated rubber hump with two-way calibrated valve in communication with the atmosphere. Hump deflates when drivers approach at correct speed. Deflates automatically for larger vehicles and therefore does not impede Ambulance, Fire Engine or Bus services. 100mm high.