In route 66 the author points out that a new car costs twice as much as a round trip continental flight

This distinction is important as it explains why road travel became so popular.

Explanation:

In Route 66, the author resets the price and all the costs that come with a new car. In this way, he shows why road traveling has become so popular. According to the text, the costs of a new car were twice bigger than the round-trip continental flight. People realized that it made more sense to go to road trips than to buy a new car.