Planetizen makes an excellent point:

In many states across the country, vehicle insurance doesn't come close to covering the cost of some car collisions. In California, along with six other states, drivers' insurance need only cover up to $15,000 in bodily harm or even death, and just $5,000 for property damage. These same minimum coverage standards have been in place for over 40 years, back when $15,000 was worth almost five times as much as it is today. When someone is hit by a driver with inadequate insurance, everyone pays.

The post provides some hard facts about San Francisco:
A report by UCSF's San Francisco Injury Center reported that, between 2004 and 2008, over $56 million was paid by Medicare, Medicaid, and out-of-pocket to cover the medical care of SF residents hit by cars (another $18 million was charged to private insurance). Among admitted patients, which made up a quarter of the 3,600 victims of auto-versus-pedestrian collisions in this time period, hospital charges averaged $47,000 to $77,000—three to five times higher than the minimum insurance requirement.

Car advocates, the post adds, respond to this criticism by suddenly caring for the poor: Without cheap car insurance, how could they own cars and get to work? The answer is simple: The money the state (meaning the public) spends to cover the real costs of car accidents involving people and property could easily go to making public transportation more reliable. The poor, in the first place, should not depend on cars, which are expensive to maintain. They would be much better off with buses and trains that were frequent and on time.
Those billions could be put to better use. Programs like the Great Streets Initiative in Los Angeles and the Vision Zero movement in NYC exemplify a more sensible transportation policy, one that invests money up front to save lives and dollars down the road. Chicago’s Ashland corridor Bus Rapid Transit and Seattle’s Link light rail expansion are also great examples.

The free roads, the cheap parking, the cheap gas, and now the cheap insurance—this is not about the market, this is about capitalism. And capitalism is always about the public paying for private profits.