The royal decrees of 9th October 1998 and 3rd May 2002 on road humps lay down the requirements and technical specifications to be met by these devices. BRRC has developed for the geometric inspection of “raised traffic calming devices on public highways”, as they are officially named, a method of measurement which allows rapid assessment of their compliance with requirements and specifications.
The law authorizes traffic calming devices with varying geometries and dimensions, but requires that they should be adapted to local circumstances (location, types of vehicle in traffic). As a result, not all specified devices (and, all the more so, those failing to comply with regulations) have the same intrinsic effectiveness in reducing speeds. That is why the choice of a traffic calming device with any ensuing layouts or facilities requires careful reflection on the objectives to be met. To collect objective input for this reflection, the Centre also makes measurements on existing sites, where both geometric data and travel speeds are recorded.
The speed adopted when driving over a round-top road hump will depend on the discomfort it generates (expressed in terms of vertical acceleration felt by the driver). A road hump should cause little discomfort at the design speed (V85), but sufficient vertical acceleration at higher speeds to encourage drivers to reduce their maximum speeds.
Raised traffic calming devices (road humps) which are meant to reduce the speed of traffic on public highways to a maximum of 30 km/h have to meet the siting conditions and technical specifications laid down in the royal decree of 3rd May 2002, which has amended a previous royal decree of 9th October 1998. The changes introduced by the new decree consist mainly of tolerances in dimensions.