Do you think more people would share rides if cars could drive themselves? If this wouldn't be the case, I can see how the technology would help parking congestion but not how it would help traffic congestion.
Self-driving cars can help traffic congestion in the sense that, if you can tell your car you don't care how long it takes to get somewhere, it might route you through a longer path and consequently help rebalance the load. Maybe.
(I don't think people will be very excited about dynamic road tolls, but I think it would be at least somewhat effective in shaping behavior)