Road restraint systems can be divided in :
• Road safety barriers: the road barriers are placed along the roadside or on the central reserve; their role is to prevent errant vehicles from crashing on roadside obstacles, and to retain them safely (Figure 2.14).
• Crash cushions: the crash cushions are collapsible structures that prevent vehicles (usually cars) from impacting specific hazardous sections, as the beginning of the central reserve. They safely stop the vehicle, avoiding worse consequences (Figure 2.15).
• Terminals for road safety barriers: Terminals are the ending part of a safety barrier; their role is to avoid those parts from becoming dangerous points for vehicles (Figure 2.16).
• Motorcycles protections systems: MPS…show more content… Especially when the vehicle is about to impact an unprotected road side obstacle. Even more important is the role of road barriers used in the central reserve in order to prevent a vehicle from crossing it and, to avoid the possibility of a frontal impact on highways or double carriage roads. They are also usually installed in the presence of a bridge or to protect exposed zones as pedestrian zones or inflammable tanks.
Figure 2.19 is an example about what a barrier must prevent if collision happens, however depending on the type of vehicle and the level of containment of the barrier there are cases where the desired performance is difficult to achieve.
Each country establishes in its national regulation which kind of protection should be used, according to the different situations that may be present on the road network, and establishes the different installation and maintenance procedures together with any additional needs not covered by the norm. Minimum legal requirements on highways of some European countries are reported in figure 2.20 (the standard terminology will be explained in Chapter 3).
Figure 2.19: Bad barrier