It is about 45 miles (70 km) from Baltimore to the NIH campus in Bethesda, MD. If I were to travel the entire distance using public transit it would cost over 20 dollars for a return trip (one way bus fare in Baltimore is $1.60, commuter rail (Marc train) fare is $7.00, and Metro fare in DC is $3.65 ($3.85 during peak hours)). That amounts to over $100 per week and $5000 per year. If I bought a monthly rail pass, then I could cut the cost down by 75% or so. Now if instead I were to drive everyday, ninety miles per day is equivalent to 22,500 miles per year. A car that could travel 30 miles per gallon of gasoline would use 750 gallons a year. At the current price of $3 per gallon, this would be $2250 per year. If I drive my car for ten years and it cost twenty thousand dollars then that is an additional $2000 per year. Insurance, fees, maintenance and repairs probably costs another $2000 per year so driving would cost about $6000 per year. If I drove a cheaper and more efficient car then I could bring this cost down to $5000 per year. Thus, driving is economically competitive with public transit. Add in the fact that I would own a car anyway even if I didn’t use it to commute to work and driving is the less expensive choice.
How is this possible? Well one cost that I didn’t account for is parking. The NIH happens to have a large campus where parking is nominally free. Although if I chose not to drive, I could receive a public transit subsidy of up to $110 per month or $1320 per year. If the NIH were located in downtown Washington DC, parking could cost over $400 per month or $5000 per year. So the real reason driving is competitive with public transit is because parking is subsidized. If I worked in an urban center where parking is expensive then driving would be much more expensive than public transit. Driving is further subsidized because roads and highways are funded by tax dollars while the cost of maintaining transit stations and tracks are only partially funded by taxes. If transportation infrastructure were publically funded or if subsidies for roads and parking did not exist then public transit would be the prohibitive cost effective option.