They can somewhat, but to get the real benefit of computer-driven cars will require that they be either centrally controlled or that they communicate with each other. If the cars do that, they can travel at high speeds (don't know how fast, perhaps 100-200 mph?) with mere inches or perhaps a couple of feet of space between them. When a car needs to change lanes, the other cars around will know it and make space immediately. If one slows down at all for any reason, the others will all know it and slow down accordingly. If the cars only get information from their sensors, they cannot work together in such a coordinated way and travel improvements will be only a small fraction of what is possible with central control or communicating cars.