From the CFR (Code of Federal Regulations) March 1979: https://www.govinfo.gov/content/pkg/FR-1979-03-22/pdf/FR-1979-03-22.pdf#page=41
§ 571.127 Standard No. 127, Speedometers and Odometers…
S4.1.4 No speedometer shall have gradation or numerical values for speeds greater than 140 km/hr and 85 mph and shall not otherwise indicate such speeds. This paragraph does not apply to a speedometer design for use in or installed in a passenger car sold to a law enforcement agency for law enforcement purposes.
S.4.1.5 Each speedometer shall include the numeral “55” in the mph scale. Each speedometer, other than a digital speedometer, shall highlight the number “55” or otherwise highlight the point at which the vehicle speed is equalling 55 mph.
The “double nickle” national speed limit was enforce by threatened withholding of Federal highway funds from any state that did not comply. Nevada was the only state that opted to forgo the Federal money.
I read somewhere along the line that the 85mph maximum for the speedo was due to research that found people are most comfortable when the speedo is reading a little above half scale. When the limit is 65-70, 120mph speedos are used, so highway speed is a little above half scale. With the “double nickle”, the 85mph scale put 55 a little above half scale.
Speed limits were lowered to 55 during the Arab Oil Embargo, when there were lines at gas stations around the block. Gas consumption varies by model and horsepower, of course, but repeated studies showed that mileage vastly decreases as cars go over 50mph.
Mileage efficiency goes down with speeds in linear fashion up to about 50, after that (again, varying by model, aerodynamic styling, etc.) it goes down asymptotically with each increment. Air resistance and rolling resistance play a significant role.
Carter, ever the technocrat, agreed to the change to save fuel during the shortage. It was about as unpopular as his “turn off your Christmas lights” dictat, but it did, in fact, save gas. Unfortunately it also cost “time”, and people didn’t like that.
I remember that the 1977 Chevrolet Impala and 1980 Oldsmobile Omega that my parents bought had 85 mph speedometers. Of course, there was a national 55 mph speed limit at the time, and the Malaise Era (1973 to 1983 model years) is notorious for ridiculously underpowered cars. The 6-cylinder base engine of the full-sized 1977 Impala had just 110 horsepower. Nowadays, 110 horsepower is what you expect from a low-end subcompact economy car with a small 4-cylinder engine. The Iron Duke engine (the base engine of the 1980 Oldsmobile Omega) has a reputation for being underpowered, yet able to run for virtually forever.
There’s now a toll road in Texas that has an 85 mph speed limit. I wonder what it would be like to drive on it in one of those Malaise Era cars. I wonder what the conversation would be like if someone driving one of these Malaise Era cars with the 85 mph speedometer were pulled over for speeding. (I’m sure that a Corvette or Trans Am could do it.) Officer, the speedometer only goes up to 85 mph! Look for yourself if you don’t believe me!
The 55mph speed limit was enacted by Congress and signed into law by that big gummit Communist (/sarcasm), Nixon, on January 2, 1974. On Sept 1, 1979, the NHTSA regulation on 85mph speedos went into effect.
I recall good ol’ Massachusetts dutifully going along with enforcing 55MPH, to get those big Fed $$$. My father got pulled over for 58. However, he passed a Smokey that was going exactly 55 in a rolling roadblock. Invective ensued, but… my older self would say, “dude, what did you expect?”
Of course, now, you won’t see a MA trooper anywhere outside an accident scene or a construction site - for which they get paid 1.5 or 2x. And so, 85 is now almost the effective minimum speed on MA interstates - get out of the left lane!
I believe Wyoming was the last hold out. They were feeling flush from oil, gas, and coal money but eventually even they folded.
Nevada’s solution for speeders was to hand out tickets for “wasting a natural resource” which didn’t count against your driving record. Prior to 1974 some sections of Interstate in Nevada didn’t even have speed limits.
I’m pushing 70. I remember when the first suggestion was made about driving 55, before it was the law. A local TV station sent a reporter out to drive a freeway at 55. Cars blew past him, until one old Thunderbird fell in line, for a few minutes, then eased past him.
I also remember a PoliSci class I had in early 73, when the Senate Watergate hearings were going on. The prof speculated the POTUS had to do two things to survive: get rid of Agnew, and start an international crisis, though he thought the Arabs might not be foolish to go after Israel again. By the following October, both had happened. Didn’t “save” the POTUS tho.
Can’t you remember 50 year old stuff in that detail? :^)
I often can’t remember why I walked into the other room. I know I went there with a purpose, but I’ll be damned if I can remember what it was. I dread taking the 5 words test at my annual physical, I’m afraid if I screw it up they’ll lock me up for good. (Arguably that should have been done when I was in a drug induced haze for a decade, but I digress.)
He was possibly the best man who was ever prez and the nicest. He took on some tough times and installed Volcker knowing he would not get reelected because of this choice but he was being responsible for the outcomes. How many of them are actually responsible first?
It’s actually true in many cases … I walked from the kitchen to the bedroom to get something, and along the way thought about something else … and promptly forgot what I was going to get. Happens more and more often.