> This is the tricky part. You need to know the worst-case scenario for the trip to the airport. This is why I love taking trains to the airport, even when they are on average slower than a taxi. You have a safe upper bound of how long it takes.

This is reasonable advice going to the source airport or NYC where subways run 24/7.

Be mindful at the destination though, when trains may not be running etc. I've had a number of close misses at SFO when the last BART out was just past midnight and a slight delay would leave me spending 4 hours there or $100+ in cab fare.