A "smart" road hump based on a rubber fabrication will be demonstrated to emergency services and other stakeholders on 2 and 3 March, in the UK.
The Transcalm hump relies on a reinforced rubber tube and air at atmospheric pressure. When a tyre runs over the tube, the air within can escape through an adjustable valve, allowing a smooth ride. However, the valve is set so that when the tyre is travelling above the speed limit, the valve remains shut, creating a hard bump in the road. Thus the Transcalm works like a conventional speed hump when the vehicle is travelling above the speed limit, but is barely noticeable when the vehicle is travelling at legal speeds.
According to the designer, Graham Heeks, a second valve in the tube will allow the air to release if a heavy vehicle hits the tube at speed. This means that emergency service vehicles can pass over the hump unhindered. The unit re-inflates after each tyre has passed over it, due to the natural spring properties of the rubber construction.
Heeks said the tube is made from a tyre tread compound, reinforced with polyamide fabric. He said a three-year trial in London had ended on 14 February, and had shown the need for more flexibility in the rubber, so the compound had been made richer in natural rubber.
Heeks' company, Dunlop Transcalm, offers two products, the 850 unit, weighs around 22.5kg, while the 1200 unit (1200mm long) weighs around 33 kg. Some of the initial development work was carried out by Dunlop GRG Ltd, which retains an equity stake in Heeks' Dunlop Transcalm company, but no longer manufactures the humps.