This is a very good analogy.
Do you want to take it back, or do you want me to tear it apart?
Be my gest, tear it apart!
Beau Gest?
Fine. In the 1970s the 55mph was, indeed, arbitrary. However, the speed limit set on a highway or road is determined, generally, by optimizing a function of a number of variables. Basically, if the limit is too high, existing automobiles and road materials result in uncontrollable vehicles. If the limit is too low, there is too much noncompliance and the speed differential causes more safety problems than the absolute speed.
Surely you're not advocating noncompliance with minimum wage?
The proper analogy is a minimum price for, say, milk or cigarettes.