On traffic capacity

When we first moved to Kirkland, I lamented the then-recently-started construction on I-405 just east of our townhouse. "This is going to go on all year," I mentioned to Layla, "and I'm sure we're going to move out right before it's completed."

Well, the construction took all year and we moved out right before it was completed. And so in preparation for a bitchy post about how unfortunate it was to have a heavy traffic construction site near our house for a year and not seeing any of the benefits, I ran across this page.

The interesting part here isn't the amount of work that they did on this onramp—it's taken them an entire year to complete the damned thing, after all. I think the interesting thing on that page is that the difference in traffic volume between weekday rush hour and weekend happy-happy-drive-time is only about 15%. That's right: 5,500 cars per hour on Monday night, and 4,200 cars during midday Saturday.

That's not a lot of difference. In fact, I strongly suspect that even with that increased 15% in density, that the whole mess would still travel at full speed if it weren't for the contention. The problem here is that everyone still tries to get on the roads at exactly the same time, creating waves of congestion that take far longer to dissipate than the incoming flow would suggest.

And that's the real problem here. We don't have any effective means for throttling departures so that the mass of people converging on our highways don't always do so simultaneously. I could imagine that very strict scheduling would possibly solve a big part of this, but that's such a ridiculously Swiss idea that it couldn't possibly work here in the land of the free and the brave.

So when you're stuck in traffic tonight (or aren't, depending on where you live or whether you work) consider how much nicer it would be to get a rush-hour lottery ticket to see if you get a 5:15pm departure or have to wait around until a 7pm spot opens up. Because either way, you'll be getting home at full speed.