Always On Time

I believe it's a Known Thing in the transit literature that riders care most about frequency. It's also a Known Thing in the human experience that getting to flights is extremely annoying, you have to add SO much buffer to be sure you're there on time. Here's why.

Imagine you're trying to get to a restaurant that's 10 mins away from you by bus, but the bus comes exactly every 20 mins (and you can't trust which exact 20 mins that will be). Here's how early you have to leave the house in order to be different %s sure you'll arrive on time:

Compare it with walking – say the same location is 20 mins away on foot, but with very low variance.

You can see how 1) if you REALLY care about arriving on time, you end up choosing the method that's slower but more reliable, 2) to arrive on time you have to throw in a large amount of buffer.

(I know I'm motivated to choose certain numbers here, but there's a widget at the bottom where you can see how the outcomes are sensitive to different assumptions).

By contrast, here's a bus that takes 15 mins but arrives every 10 mins: if you're trying to hit above 90% confidence that you'll arrive on time, you prefer this bus even though it's 50% slower in the best case scenario.

Here's the widget so you can play with it (on web):

And this is why airports are extra-annoying. Missing a flight is extremely expensive and annoying, in both time and money – you can never reach 100% certainty of arriving on time, but you might plausibly be aiming for 99% or 99.9%. And getting to a flight often involves multiple stacked waits: a subway to a train, and then a wait for security at the airport. This is why you end up (most times) waiting hours at the airport.

I understand that airlines have an incentive to make money rather than make me happy, but so much of the stress could be reduced if it were easier to (say) miss a flight and take the next one – trying to go from 99% sure you'll be on time to 99.9% sure requires so much extra buffer, which wouldn't be necessary if it the cost of missing the flight was lower.