Quote:
Originally Posted by rypinion
Steve's point is that the fact that they plan for 10 over is exactly what causes people to drive 10 over. Speed limits should be "enforced" by the geometry of the street in concert with the posted speed limit.
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Another way to control speed would be to hang logging chains from the underpass, forcing drivers to slow down to avoid chains going through the windsheilds. But I doubt any engineer would sign off on this scheme either.
So an underpass geometry is designed to limit speed to a given rate. If those rates are exceeded, collisions, and likely some deaths occur. How many deaths are acceptable?
See the engineer's logic here? By designing the roadway for the speed limit + X%, the city removes liability.
Safety factors are used across the board in every single branch of engineering. Every engineer is trained to use established safety factors. To not do so would be considered irresponsible and would surely result in dicipline.