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I hate to mention it, but your analysis is incomplete. It leaves out the following-time factor, which is another "individual versus group" issue.

More space is required between vehicles at higher speeds. Therefore, free-flow speed (u_f) is a different parameter from optimal speed (u_o). Setting a speed limit without consideration of the latter parameter is ignoring road capacity, and the overall efficiency issue. If you've ever been delayed by traffic, you'll realize that not all trips go at the speed limit.

I think that many people have difficulty picturing this....most would likely say that a higher speed limit would allow more traffic to get through a stretch of road in a given amount of time, but it's not true. Perhaps one way to illustrate it is using an extreme--imagine if cars were going 550 mph. You'd see few cars on the road with such distances required between each. If you were one of the lucky ones, on the road, your trip would be short...but most people would be sitting in traffic.

So overall, those on the highway would be costing others a lot, by the points you have made. The key might be a variable limit (e.g., West Texas).

I'm not advocating a "needs of the many" approach, but simply stating facts based on calculus. Disclaimer: Though I did get a very little formal training in traffic engineering LONG ago, that's not the basis for this post, and I am not a traffic engineer!)

Obviously you don’t drive on the national Highways! When have you ever seen anybody drive the speed limit, keep a safe distance etc. Dropping the speed limit will cause a surge in deaths because you will have the slow pokes driving at 55 and the rest driving at 75 or 85 miles an hour. I don’t like needless laws that say they are trying to protect me. I don’t like seat belt laws, helmet laws. This is not the job of government! We have so many laws now you can’t hardly turn around without breaking some law somewhere!

Perhaps one way to illustrate it is using an extreme--imagine if cars were going 550 mph. You'd see few cars on the road with such distances required between each. If you were one of the lucky ones, on the road, your trip would be short...but most people would be sitting in traffic.

If the speed limit on an expressway with a metered entrance were set at 550mph, and if the goal was to keep traffic on the expressway moving at top speed, the allowable rate of entry would indeed have to be slower than if the speed limit were lower. On the other hand, in more practical scenarios, vehicle speeds will be determined by traffic density rather than vice versa. I'm not quite clear how the actual speed of travel on a road would exceed the optimum speed under such a scenario.