From Central London to Heathrow Airport, the Underground is reliable, though it takes over an hour. If you're running late, it's tempting to jump in a taxi. But if you do, chances are you'll get stuck in traffic, and miss your flight. If the taxi was your only hope, then fine, but if you still had a chance on the metro, that would be less variable. You could still make it if you run.
When we see something that could be shorter, or more elegant, it often ends up taking longer or adding complexity.
When time's running out, don't take shortcuts. Remove variables instead.