Paradoxically the slower speed gives higher traffic volumes and quicker journey times.

Not a paradox. The paradox is that humans think they can get somewhere faster by driving on each other's bumpers. If you watch expressway traffic from a hilltop at night, you will soon discover the true herd pattern of human behavior. Many people do drive hundreds of miles in bumper to bumper traffic that is really just the pod or herd of 10 or 12 cars and trucks they have trapped themselves within.