This, and reliability. If I have to leave home 15–20 minutes earlier just because it is _very_ likely that the train gets stuck in a tunnel due to signal malfu

This, and reliability. If I have to leave home 15–20 minutes earlier just because it is _very_ likely that the train gets stuck in a tunnel due to signal malfunctions, or crawls from one stop to the next, I might as well use alternative means (i.e., a car).