The fundamental problem with cars in cities is that they make each person take up a crazy amount of road area: http://lh3.ggpht.com/_9F9_RUESS2E/S7tbclwxiPI/AAAAAAAACmw/uI...
* traffic problems will be significantly reduced * you won't need traffic lights like they exist today * the vehicles can be reduced in size (double occupancy perhaps); a family can just order a couple cars and have communication between them * streets can be reduced to fewer lanes; possibly one-way because the vehicles can navigate the best route in any case