Remember that it's against the law to leave children alone in a home under a certain age, and alone at night at a higher age. I can't imagine it being okay to have children alone in a self-driving moving vehicle, with their door locked to prevent them from exiting in an emergency, and no adult to help them.

Back in 1900, people had only two kinds of habitats - dense cities, like Boston, NY and San Francisco, and rural areas with lots of elbow room. Freeways allowed for urban sprawl - moving people and manufacturing out into what was farmland or open spaces. California now has a lot of people spread out with medium to low housing density, San Francisco being the exception with very high density. The freeways that once allowed speedy travel from Sacramento to San Jose are now a traffic nightmare, as all these people travel from their low density housing areas to either other low density employment areas or urban cores. Instead of living like cattle in a city, they live like cattle in their car, commuting. But what about those lower density states, like Montana and Kansas, with fewer total people? When you have smaller communities with lots of elbow room, the per-capita cost of improvements is higher. Freeways, Postal Routes, water, gas lines, power lines, and even high speed data lines are relatively more expensive because there are fewer people to spread the cost over.