When I was thinking of the dumbest things on cars mandated by governments, I went straight for bad headlights and stupid automatic seatbelts. And I totally forgot about another silly and short-lived U.S. requirement: the 85 mph speedometer.
Lasting between 1979 and the early 1980s as a law, the 85 mph speedo did not have the intended result of actually making people drive no faster than 85 mph. And look what we have today, 160 mph-speedos in a 2.0-liter Passat TDI. That's so useful!
When I was young, I usually saw these 85 mph speedos in cars like the Buick Century and Ford Tempo and assumed 85 was really as fast as that car would go. That's totally believable. But then you remember that fast (for the late '70s/early '80s) cars like a Corvette or Porsche had these things.
Leadbull illustrates the problem:
"Sir, do you know how fast you were going?"
"No, I clocked you at 120."
"But the needle said 85."
Someone who thought the 85 mph speedometer was a good idea should've made like an 86+ indicator.
Officer: "Do you know I clocked you at 86+?"
This is why digital speed readouts in cars caught on, isn't it?