Traffic Volume vs. Commute Time

Warning: this is a rant. I’m not expecting people to take it seriously. All helpful suggestions and critiques will be regarded through the lens of someone who’s ranting.

The Washington DOT keeps a huge amount of data about traffic that travels the state and Seattle is wired within an inch of its life. The result of all this wiring is a very nice tool that tells you how bad the traffic is right now and an annual report that talks about the traffic in the state. 

I’ve been noticing that my commute is taking longer no matter when I leave (except when I leave at 11AM or 11PM at which point the 12 miles takes about 18 minutes at the speed limit). When I started at Microsoft in 1998 my inbound commute took about 35 minutes; now I have to allocate 45. My homeward bound commute took about 45 minutes; now I allocate an hour.

I wanted to see if this was just my perception or reality, so I turned to the state’s data. I can’t admit to having spent more than about 15 minutes with the data, but I realized some problems with it. First off, the annual report only talks about numbers of cars per day that travel by certain mileposts, and by that metric traffic isn’t getting worse. That’s right: traffic volume is flat.

But I know that my average commute time has increased. The problem? Volume != commute time. The report is simply telling me that, since about 2001, the route I travel has been saturated.

Great. I hate data. I’m going to just keep telling myself that, based on data, my commute clearly isn’t getting worse. Or maybe I’ll take the bus, which turns a 45-minute commute into a 75 minute commute for me.

Comments (5)

  1. Taking the bus has one advantage. You can spend those 75 minutes reading, writing email, or watching Sir Ken Robinson videos 🙂

  2. wpfedevcon says:

    As you well know, the WSDOT Seattle Area Traffic Map is a hugely popular Web site for area commuters. Interestly, WSDOT has archived the traffic map GIF images every 10 minutes since January 2004. I’ve created a WPF app that animates the images for a selected time period. It’s pretty interesting to see a time-lapse sequence of traffic patterns.

    If you’re running Vista, or XP SP2 with .NET 3.0, you can download the app from:



  3. Angel Amador says:

    Convince your boss that you should be allowed to work from home.

  4. Ripper says:

    I would definitely consider mass transit.  Like Aaron said, you can at least do other things (provided you don’t annoy the other people around you!)

  5. Ed Kaim says:

    Why don’t you just drive to work in the afternoon and drive home in the morning?


    Like the guy in the $3000 suit is going to listen to the guy who spends that much on gas waiting in traffic. Come on!