Speed limits in the earlier part of the 20th century had been determined at the time of the
opening of a new road - by officials observing what speeds the drivers were using when
driving the new roads, then striking an average.
No kidding - talk about "reasonable and prudent"? They actually based speed limits on what
speed the average drivers felt comfortable actually driving on the roads at!
With the post-war rapid development of modern cars and their ability to attain higher and higher
speeds, that all changed of course. In fact, speed limits could actually have been claimed to be
for "safety's sake" then, an effort to lower the frightening highway casualty rates caused by faster
cars on modern highways, not to mention equipment component failures, tire blowouts, all sorts
of things related.
But when the various law enforcement agencies at state and local levels began being utilized as
sources of revenue generation, most practical applications of determining speed limits went out
the window, replaced by politically-determined ones.
To this day, most speed limits you'll encounter during a typical day are not actually engineer design-
determined ones, but rather ones set by governmental agencies (or just as often, elected bodies).
Sole purpose? Revenue.
I learned all this stuff in the years I worked for a civil engineering firm in the DC area.
I routinely applied state and local design criteria when laying out new roads and such and saw the
decades of data used to determine the limits of the physical dimensions of things...
and that data always included references that said standards were derived from, which I spent a
lot of time reading and researching.
Conclusion?
Safety has diddly squat to do with determining speed limits. Design and engineering doesn't have
much influence on them either.
What does? Revenue and politics.
Hence, why speed limits have always been "serving suggestions" to me.
