1 entry tagged traffic, newest first.
Four thousand drivers, two routes, sixty-five minutes each. Open a new road between the two halves that takes no time at all to drive, and every one of them takes eighty. Nobody is behaving badly and nothing is congested by accident: the eighty-minute outcome is the only stable one. This page works the whole thing out in exact fractions, shows that the harm exists only between three thousand drivers and nine thousand, peaks at exactly 22.5 minutes, and lands on the same four-thirds that bounds every network of this kind.