Watching Traffic

Wednesday, 10 October 2012, 11:35 | Category : Life, Philosophy
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I graduated from a small liberal arts college. I’ll get back to that.

This morning on the way to work, as I merged onto the Natchez Trace Parkway for the short segment that emptied onto the interstate, I began to look at the traffic (not for the first time) not as cars but as packets of information, flowing (or not flowing) on a network. Getting on the Trace wasn’t such a big deal; most of the traffic was merging, with just a few cars upstream. So except for the occasional ornery upstream driver who wouldn’t slow down and let you merge, things proceeded apace, which on this stretch of the Trace is 40 mph. A mile or so down the road, it gets more interesting, as you get off the Trace (which everyone has to do at the moment, because the Trace is closed at that point) and merge onto the interstate. You come into a lane on the far right, which will end in about 300 feet. You move to the left one lane, but that lane, in about 1000 feet, will veer to the right onto the bypass. So you have to move at least one more lane to the left to continue south. And if you’re smart, you won’t stay in that lane either, because another 1000 feet or so beings you to an interchange, with traffic leaving the interstate and more coming on. So it’s another move to the left, or maybe two, which would put you in the far left lane. This, you would think, would be the best lane if you’re going several miles down the road. Unfortunately, that’s most often incorrect. The middle lane of the three going south seems to often move faster, which flies in the face of reason – but Mississippi drivers don’t use reason when driving. Lane-changers are constantly moving from the center lane to the far left lane, which means drivers in the far left lane are then constantly having to slow down, because of course when you change lanes you have to then slow down just a little. This results in the center lane often having big gaps where you can maintain a decent speed, and the far left lane sometimes coming to a near-standstill. There is still a benefit in being in the far left lane – idiots changing lanes without looking can only come at you from one side (the right), and you have a small margin of safety if/when they do. But I digress – this is about traffic flow. Or really, about how I see networks everywhere. I was watching cars merge, and change lanes, and thinking about how networks behave when they get crowded, and how they don’t have packets randomly changing lanes – at least, hopefully they don’t. All highway engineers can do is design roads and interchanges, and then hope for the best. Networks can be designed, and then actively managed. We’d probably all get to work faster if the engineers could actively manage traffic.

Anyway, I said I went to a small liberal arts college, where I studied math and physics. One of my math professors considered teaching a class in queueing theory one semester. None of us, the small number of math majors, were really interested – we couldn’t see any reason why we would want such a theoretical class – so he dropped the idea. I wish he hadn’t, and I wish we’d been interested in taking the class. I sometimes think the world might make more sense to me now. Or at least, I might understand what passes for the underlying logic of things moving around me. Once again we find that youth is wasted on the young.