Flew into Dulles airport today evening and found the line for taxis snaking all around the concourse and doubling back.
"Why is so crowded?," wondered the lady behind me in line.
"It's always like this when it rains in DC," I informed her with my best weary-traveler tone of voice.
"But why?," she persisted, "if it's not raining, how do all these people get home?"
That had me stumped. It's a good question. Why do the lines get atrocious whenever there is rain? To give you a perspective of the problem, the line's usually under a dozen on normal days. On a rainy day, it tops a couple hundred. And yet, people who're going to take a taxi from the airport are going to take a taxi, right? It's not like they're going to walk out on the Leesburg turnpike and trudge home because it's a sunny day ...
Thinking more about this (I had over an hour to think about it) ... it's not the airport that's the problem. When it rains, folks in downtown DC who'd have normally walked or taken the metro probably decide to take taxis. And since taxis make more money on multiple short trips, that's where the taxi drivers go. And so, there are fewer cabs to service the airport. That's my hypothesis anyway.