QOTD: What’s Up With This Vega Speedometer? When Did US Speedometers First Start Also Showing Km/h?

Tom Halter has a good eye and left the following comment today at the Vega post about its speedometer:  I like how instead of having a separate scale for km/h, they just converted the mph markings to their metric equivalents. Really helpful for places where the speed limit is 97km/h!

Yeah; pretty odd indeed. I answered him that I thought it was a way of introducing Americans to the metric system, which in the 70s was being pushed hard for universal adoption. But after checking, that push, the Metric Conversion Act of 1975, was obviously post-1972 Vega, although there was a previous US Metric Study of 1968 that already encouraged and anticipated metrication in the US. But I’m having a hard time connecting that to the Vega’s 1972 speedometer. Or to anything else logical.

Yes, using exact km/h equivalents was quite odd. Can anyone explain it? I’m thinking it’s just more of the wacky thinking that predominated much of the Vega’s difficult birth.

And by either 1975 or ’76, the speedometer was updated with the more typical dual scales.  Which may perhaps reflect that the 1975 Act required that if both are shown, they need to be in a logical way?


Let’s not forget that there was a time when signs like this were to be seen in the US.

So the second part of the question of the day, which I ask in all seriousness, as I can’t find a ready answer, was there a specific mandate and year for when dual-scale speedometers had to be implemented in the US?