Self driving cars will be expensive and the grid-like system that would be necessary for them to run safely will add more costs. No space will be freed up unless people stop going places. If you see the elimination of public transit as a result then that would add even more cars to the roads. Road traffic will slow down as self-driving cars will go the speed limit. Pedestrians and cyclists will learn that the self-driving car will stop to avoid them. Those still driving their own vehicles will be able to drive past backed up traffic and change lanes in front of a self-driving car, which will stop to avoid a crash. I can imagine a row of self-driving cars brought to a standstill as human driven cars drive around them. This will lead to attempts to ban human driven vehicles. If this happens it is likely you will have to sign up for a monthly plan to have access to the road. You will need to pre-book and changes in your plan will have to submitted for approval with a surcharge.