I would write the song first and then decide the title. If you try to write the title first you might feel a little cornered into writing about the title whatever it may be. If you write the song first you can write about anything and not have to worry.
it explains why road travel became so popular.
Explanation:
The author resets the price of a new car and all the costs that involve its purchase, in a certain part of his work. With this, the author wanted to show why road travel became so popular. He shows this by saying that the costs of a new car were double the round-trip transcontinental flight, so people didn't find it helpful to buy a car and preferred road trips.