Monday, January 10, 2005

Blue Van blues

I caught a SuperShuttle from the airport. I'm tired and anxious to get back home soon. As usual I pay attention to the route the driver takes. A classic case of the "traveling salesman" problem, he (I never met a woman driver on this company) has to minimize the time spent driving and maximize the efficiency of his drop-off route. I like to see what solution they come up with, most of the time finding myself disagreeing with the choices, thinking "I would have dropped this one and then that one. This makes no sense." It also reveals new routes, short cuts and small tricks that make one feel more at home in any town.

This time, the driver is silent as one of the passenger, a woman in her sixties seating in front next to him, is telling him the best route to go to her place. He made the rookie mistake to tell her that she was the first to be dropped off and she feels entitled to give him complete directions. He nods, shakes his head and otherwise answers in monosyllabic words. "Yes, yup, no, yeah, right". She keeps talking. I'm watching as we go from Georgetown to Q Street to Dupont Circle to New Hampshire Ave to 21st street. I'm the only one left and the driver turns to me to get my exact address (all he knew until then was that I lived in Mt Pleasant). We're soon on our way and I compliment him on his choice of route. "Even if you dropped me last", I say, "this route was the most efficient route there was. I don't usually agree with the drivers but here, it was perfect". His answers surprises me. He is predictably very happy, but it is also quickly clear that he has put a lot of thoughts in the problem. He tells me that he studied the city until he got it memorized. When he gets the addresses of people, he can see them on his mental map and it becomes obvious which is the shortest way. Then he adds, half laughing "I'm also driving faster than most".
I tell him the story of a driver I once saw with a GPS and went from the airport to the closest point as calculated by the GPS, then the closest point from there, ... and so on. The problem was that, the closest point in distance may not be the shortest drive and we ended up crossing bridges here and there, and driving around for a while. The whole trip took more than an hour.
He laughs at my story. Yes, he knows about drivers with GPS. Useless when one doest not think as well, he says.
In a way he has solved the problem that still bugs mathematicians . He does not use complicated algorithms. He just knows the answer. Plain and simple.

We're in front of my place in no time. He helps me with my bags up to the front door. I ask him where he is from. "Lebanon", he says with a wide smile. "Where in Lebanon?" I ask, "I have friends from Lebanon". "Beirut" he answers the way I answer I come from Paris as if there was no other city in France. "Well, this is why you drive so fast and so well" I venture, "it's a survival skill". He laughs as he enters his van, now on his way to pick up people and drop them at the airport. A slightly modified version of the same problem.


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