Speed limits don't work, reprise

In a previous post, I commented on how speed limits don't successfully regulate traffic speed. On my drive home today I realized that if they did successfully regulate speed, they would be problematic.

Speed limits often apply to long stretches of road, which typically include straight and curved portions. On a curve, of course, some of the tires' griping force must be devoted to turning the car; on a straight road all of the grip can be applied toward propelling the vehicle, or stopping it, should the need arise. So, straightaways can safely be driven faster than curves. The condition of the road may vary widely, too, within the area of a single speed limit. Inclement weather must also be considered, as must lighting and other traffic. I'll leave to the side considerations on the type and condition of the vehicle, and the skill and condition of its driver.

The point of all of this is that applying a single speed limit to a stretch of road within which these variables vary is misleading, as it suggests that the entire stretch can be driven at that speed. A driver following this suggestion will then either take some portions of the road too fast, or other portions too slow.

What's the solution? Short of a fully automated roadway system with fully automated cars, I don't know, but it certainly isn't more speed limit signs.