"Michael Pardee" wrote in news:3bmdnehpZ5gS3QHbnZ2dnUVZ snipped-for-privacy@sedona.net:
Canada is the only country in the world that has 5mph bumpers (and one of only TWO countries in the world with any sort of bumper standards at all).
There are no hydraulic rams anymore, just styrofoam atop a rigidly- mounted steel beam. The rams were too heavy and were a casualty of CAFE- derived weight-saving measures.
The whole point of the energy absorbing bumpers was to protect the car's "safety systems" from damage in a collision at that speed. "Safety systems" primarily means the headlights.
The automakers were able to have the US standard reduced in the mid-'80s because they were able to show that there wasn't much practical difference in damage between 2.5mph and 5mph bumpers.
2.5mph bumpers were supposed to be able to be less costly to produce and carry less of a weight penalty.Also, rigid bumpers tend to carry more of the stress of the collision to the body shell, meaning damage is more likely to go deeper than just the cosmetic. The old non-impact bumpers tended to keep the damage out at the cosmetic sheet metal.