For months now, we’ve been tracking the fact that vehicle travel in the Northwest—both in general, and on specific urban highwayshas been surprisingly flat for years, even decades.

One of the most common reactions to this news has been:  well, duh, there’s a recession on. A few folks have argued that once the recession lifts we’ll see vehicle travel resume its steady ascent.

I think that misses the point of what we’re finding.  The slowdown in vehicle travel started long, long before the current recession began. In fact, it started back when the economy appeared to be humming along quite nicely.

The graph to the right shows it best. Total annual vehicle travel in Washington and Oregon grew steadily for many years. Then, in about 1999, growth started to moderate. And after a few years of slower-than-average increases, traffic volumes essentially plateaued in 2002.

Since 2008 we’ve seen driving dip, tick upward, and then dip again—which is perfectly consistent with what’s happened with the economy and fuel prices.

But the interesting part of the story isn’t the recent trends. It’s what happened about a decade ago to make the VMT curve flatten out.

  • Remember, there was a bit of a recession in 2002—the year of the VMT plateau. But from 2002 through 2007, unemployment in the Northwest fell steadily, even as the population of Oregon and Washington grew at a steady clip.

    But still, despite increases in both population and economic activity, VMT in the two states barely budged from 2002 until the recession began.

    I’ll leave it to some future PhD student to figure out precisely what caused the shift in VMT trends in the late 1990s and early 2000s. I have lots of theories:

    • Major urban highways hitting capacity constraints;
    • Increases in gas prices, coupled with a growing belief that gas prices wouldn’t ever hit the lows of the late 1990s again;
    • Demographic changes, with more senior citizens and smaller families leading to less driving per person;
    • Land use shifts that let more people walk, bike, or take shorter, chained car trips for daily errands;
    • Possibly, declines in new road construction;
    • An increase in flexible work schedules, with more people working from home on some days;
    • The internet cutting back on shopping and/or work trips;
    • Cultural shifts that substituted tech toys for cars as objects of desire; and
    • Economic shifts, with fewer teens working (or looking for work) and widening income disparities that made it hard for some folks to pay for cars and gas.

    Those are just theories; some are probably wrong.  But regardless of the precise reasons, the trends themselves are clear enough. The “Where are my cars?” story doesn’t simply follow the trajectory of the recession. It’s a more complex story, with older roots.