[zbanks]

It's also been shown that you can maximize the throughput of a highway if the speed limit is 45mph. Too high, and you need to increase the space between cars.

Although 55mph != 45mph, it's pretty close. It also doesn't serve the individual, but if can't get the cars through fast enough, the traffic will build up eventually.

[daniel-cussen]

You could change the speed limit dynamically to always maximize throughput.

[vl]

Major Seattle highways have variable speed limits now, same constant traffic jams as before.