When people talk about cost of car ownership, they include the capital cost of the car, the cost of fuel, insurance, and roads, but they almost never consider the cost of cleaning up after the car. If motorists had to pay to remove from the atmosphere the pollutants they spew into it, gas powered vehicles would be much more expensive. Instead, they leave this cost to the future.
Manufacturing a car has a hefty carbon cost. It may be higher or lower depending on the type of the car, but in general for gas cars may it's about the same as the pollution caused by driving it around. A car may drive about 160,000 miles during its lifetime. If it gets 38 mpg, for example, that will consume about 4200 gallons of gas, and each gallon has about 20 lbs of CO2. Over the lifetime of the car, that will cause 42 tons of CO2 pollution. There is a lot of debate about how much it costs to recover the CO2 from the atmosphere, from $50 to $600 per ton, so it is difficult to translate directly into dollars, but somewhere from $2100 to $25000.
What are some policies that might address this? Here's a sampling, but many of them would work much better at the state or national level.
Gas tax. This is traditionally how we pay for roads, and the gas tax has been kept small partly because it is regressive. But a higher gas tax would discourage driving, and the proceeds could go to programs that would reduce the cost of alternatives, such as rebates for electric cars. If you assume the social cost of carbon is $75/ton (as set by the State), the tax on a gallon of gas would be $.66, or a third of one dollar, just to pay for the carbon. The state and federal government currently both levy a tax on gas, the state rate is $.495/gallon, and the federal tax is for $.184/gallon, and the proceeds are applied to road maintenance. Presumably the tax could be phased in over time. There are issues with applying such a tax to a small area, since consumers will just drive out of the area to buy gas. However, the city, county and state all have the right to levy such a tax.
Vehicle sales tax. Having a tax you pay upfront when you purchase a new car, or bring a car into the region, makes sense, since purchasing a new car is committing to all the pollution it will cause during its lifetime as well as the pollution from manufacturing.
Road usage charging. This is also called Pay Per Mile. The State has been studying this as an alternative to the gas tax, in order to insure that electric vehicles pay a share of road maintenance. It could also be used to charge for the pollution caused by driving as well, but this would be difficult as a local program.
Vehicle license fee, aka "car tabs". These were eliminated by I-976, but since I-976 was struck down, car tabs can be reestablished. This could be done as the Sound Transit portion was, so that the fee increases with the value of the vehicle. It could also apply a scalar based on the pollution caused by the vehicle, so that vehicles that pollute less, pay less. This is essentially a flat fee for the year, though; clearly, a per mile approach would be better.
Carbon tax. A carbon tax would apply to vehicles as to other uses of fossil fuels, including natural gas.