Dynamic deflection is the second parameter to evaluate system deformation upon impact, and it is calculated as the distance between the front of the system before impact and its maximum displacement after impact. The dynamic deflection is measured in meters.
The picture below shows the definition of dynamic deflection.
It is up to the national regulations to define the criteria that the designers of the roads must follow in order to select the maximum dynamic bend for a specific roadside.
Source: European Union Road Federation – www.erf.be