I take their meaning to be this: right now, the government subsidizes a form of transportation because there's no effective way for the costs of allowing it to be internalized. (Having a toll plaza on every intersection is obviously impossible.)

With driving cars, it will become much cheaper to engage in trade centered around automobile transit. Sensors, tracking, mutuality agreements between road owners and car makers. It's plausible that all existing transit subsidies could accumulate to the road owners through market pricing, not government handouts that we have difficulty establishing the true value of.

Spending vast amounts of money on interstates is a waste. Railroads are a much better solution than a fleet of 18 wheelers. If you had to pay the actual cost of driving accross the country, high speed rail becomes a viable option.