The 85 mph speedometer

Our family's early 80s Oldsmobile Cutlass had a speedometer similar to this Cadillac speedo.

It really didn't make a difference on the Olds, but other, much faster cars had them too.  Like the Mazda RX7.

And this Mercedes 450SL.

So what gives?  Well, in 1979, the U.S. federal government required cars sold here to have 85 mile per hour* speedos and something to alert the driver about the 55 mph national speed limit.  This was during a time when fuel economy and hyper-safety were of paramount concern (to regulators).  Now, I'm personally a big fan and admirer of Joan Claybrook, the then head of NHTSA (National Highway Traffic Safety Administration), but I think it's clear that this was a bad idea.  Soon, the rule was retracted.  And we're left with these relics.

*85 miles per hour is about 137 kilometers per hour.