In several countries there is already some regulation specifying the technical requirements for an underride guard, but the accident statistics show that these requirements are not adequate.

The regulation number 58 or the Economic Commission for Europe of the United Nations, issued in 1980, establishes in Europe the requirements for good vehicles, trailers and semi-trailers regarding their rear underride protection:

• E.C.E. Regulation No. 58 ("Uniform Provisions Concerning the Approval of Goods Vehicles, Trailers and Semi-trailers with Regard to their Rear Underrun Protection")

The technical requirements of this european regulation have been adopted by several countries, including Brazil (RESOLUÇÃO CONTRAN No. 805/95).

In the United States the issue is regulated since 1998 by the new Federal Motor Vehicle Safety Standards number 223 and 224:

• FMVSS 223/224 ("Rear Impact Guards"/"Rear Impact Protection").

The picture below shows the most important geometrical requirements of the european and american standards.

 

Dimension FMVSS 223/224 (U.S.A.) E.C.E. R58 (Europe) Proposed by the Impact Project Dmax(mm) 305 400 0 Hmax(mm) 560 550 400

The distance D (305 mm for the american standard, 400 mm for the european) corresponds in the practice to the distance that the car will ride under the truck before touching the guard. Considering that the car front end will crush during the impact, passenger compartment intrusion could happen even if the guard resisted the impact.

To assure minimal penetration of the car under the truck, this distance D should be zero.

The ground clearance H (560 mm for the american standard, 550 mm for the european) is also too high, because the guard would be above the front bumper of most cars currently on the market (see "How to define the ground clearance for a safe underride guard").

The picture below shows the low static load capacity required by the cited standards and the proposal of the Impact Project (see "Estimating the forces acting during a collision").