* Most robocars, if we are efficient, will be small light vehicles meant for 1-2 people, with a few larger ones for 4-5 people.
* Small, lightweight vehicles require far less expensive road. Various estimates I have seen for multi-use paths suitable for people, bikes and golf carts range around $100K to $200K per mile, though I have heard of projects which, thanks to the wonders of government contracting, get up to $1M per mile. On the other hand, typical urban streets cost $2M to $3M per mile, an order of magnitude more.
Transitioning to Small and Light Electric Cars
Electric bicycles and Scooters are able to drive 65 mph on small battery packs that are we are technically able to produce in large volumes. China has 140 million electric bicycles now and is adding about 25-30 million more each year. Light weight 3 or 4 wheel electric vehicles like the Aptera
The Aptera 2 Series will be a two-seat, three-wheeled passenger vehicle. It is planned to be available in both all-electric (2e) and series hybrid (2h) configurations, at prices ranging from mid-twenty to mid-forty thousand dollars. By mid-2008, aerodynamic optimization using simulations and light-weight composite construction yielded a prototype which allegedly consumed only 80 Wh/mi at 55 mph (89 km/h), less than half the energy needed to propel the EV1 or the Tesla. The April 14, 2010 press release revised the design intent vehicle efficiency estimate to about 200 Wh/mi, 100-mile (160 km) range from a full 20 kWh battery pack, or around 200 mpg equivalent
Vehicles like the Aptera or the XO2 folding scooter could be mass produced and massively subsidized and provided one current lane of road. That one lane would be split as smaller narrower vehicles could be sized to fit in half a current lane of road. Larger vehicles could be disincentived using the EZPass system to charge large vehicles when they are on the road during commute times and the charges would increase for those who choose not to use the small electric vehicles for commuting when the electric vehicles have reached a high level of availability. Half road width vehicles would need to be about 3 to 3.5 feet wide or less.