Stuff my father-in-law says: On taking the train

My father-in-law was planning on taking the train to the airport. He heard that the train comes every ten minutes. By his calculations, then, he could catch the 7:50 train and be at the airport by 7:55.

Reasoning: Since the train comes every ten minutes, then it must take five minutes to get to the airport, and five minutes to come back.

Logic!

(If true, then it means that the train travels at around 170mph ≈ 270kph.)