The Infinite Improbability Drive

Filed under: @ 12:59 pm

There are 22 controlled intersections on the approximately 10 mile route that I drive home from work, 25 on the route I drive to work (don’t ask why I take a different route to work than I do to get home, it’ll just make you dizzy).
So seeing as there are literally millions of variables, starting with the simple: i.e. the light being either red or green (I count amber as “red”) and expanding to the incredibly complex: i.e. the amount of traffic going in the same direction that I am, the amount of traffic going in the perpendicular direction, and, to a certain extent, the time of day that I leave work….

What are the odds that I’ll catch every single one of those damnable traffic lights RED? And, if we assume the odds as being fairly equal that I’d catch every single one of them green, why is it that I seem to catch them all red one hell of a lot more often than I catch every single one of them green?

Since I started keeping track about 18 months ago I have had an entirely green trip exactly once. I have had entirely red trips maybe as often as once a month.
If there’s someone out there with a better head for statistics and probabilities than I, I would welcome an attempt to explain. Just the thought of trying to put together the mathematics of this makes me want to hide in a corner and whimper.

I think I need more tea. 😛

3 Responses to “The Infinite Improbability Drive”

  1. fisherbear Says:

    Sure. If the lights weren’t synchronized, and if each one allowed equal traffic flow in both directions, you’d have to drive the same route every day for about 6,000 years before you ever saw either an all-red or all-green commute. That’s with 22 lights each way. (I think we can put the similarity to Cardinal Ussher’s estimate of the time since Creation down to chance.) If you have 22 lights one way and 25 the other, that adds another few thousand years to the estimate (but doesn’t quite double it.) With 25 lights each way, you’d have had to start out dodging Neanderthals to have a fifty-fifty chance of a single solid-color commute by now.

    So, the conclusion is inescapable: these results are not attributable to chance. The highway department is messing with you. 🙂

  2. fisherbear Says:

    Bah – I shouldn’t do math after midnight. Divide those estimates by two.

    The conclusion holds though. 🙂

  3. Margaret Says:

    >>So, the conclusion is inescapable: these results are not attributable to chance. The highway department is messing with you.<<

    See, that's what I thought. And if you add in the fact that I only work three days per week…..

    Makes me want to go searching through, and under, my car for little GPS tracking devices.

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