What is Normalised Working Width?
Normalised Working width is a measure of the deformation of the barrier under impact. It is usually considered as the main parameter to calculate the space needed behind the barrier in order for the system to work properly. It is calculated as the maximum distance between the traffic face of the barrier and the maximum deformation of its main components during the impact of the heavier vehicle. The working width is divided into 8 classes from W1 to W8 according to the growing deformation of the system.
The table below provides an overview of the different working width classes and the equivalent values in meters.
Ultimately, it is up to national regulations (not the EN 1317) to define the criteria that road designers should follow in order to choose the most suitable width class while designing the roadside.