This is a followup to a thread I cannot find, in which I mentioned that the 55 mph speed limit had been preceded by 50. I cannot find that thread – Search seems to be a tad wonky.
A search in the NYTimes Index produced the following. Nixon started off by imposing a speed limit of 50 on government vehicles, requested state laws, requested voluntary citizen participation, and requested Congressional authority to implement a national limit. Many eastern states complied, starting with highways with special commissions (such as the NJ Turnpike) which could change the speed limit on their own authority, and trickling down as state legislatures acted. Most western states did not cooperate.
One issue raised was, indeed, that 18-wheeler gearboxes were such that 50 was less efficient than 55.
Eventually, the thing was passed by Congress, but the final figure arrived at was 55. The eastern states that had gone to 50 quickly moved up to 55.
John W. Kennedy
“Compact is becoming contract; man only earns and pays.”
– Charles Williams