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This is data I’ve been chewing on for a bit in support of my last chapter, and I thought I’d share it with you.  My definition of sprawl is simple: is traffic the most obvious and useful mode for the majority of trips in that place?  Then it is sprawl/.  I know this gets a lot of false positives, but I like a simple rule rather than a complex one for explanatory value.  I value parsimony.

The National Household Travel Survey (NHTS http://nhts.ornl.gov/det/) is a periodic sampling study put out by the DOT since 1965 whenever they can muster the funding to collect the data.  After the first transportation equity act, ISTEA, in 1992, they began to take walking and biking seriously as transportation modes.  I’d love to know what the national biking picture was in 1965, but the data was simply not collected.  Bikes were seen as toys then, anyway.

Three big things happened since the 1992 ISTEA.  We spent 1-2% of our 11-figure annual transportation budget on bike and walk ways, rather than just spending 90% on traffic and 10% on transit.  We also had a great recession, which forced a lot of people to reevaluate their ability to pay the $8,500 average annual cost of cars.  The cost of gas also spiked in 2008, right when the economy was collapsing the fastest.  This put a temporary halt to the sales and even use of SUVs.  Small cars, hybrids, and even walking and biking were suddenly fashionable.

During this time, there were three NHTS, in 1995, 2001, and 2009. All but the first of these was right after a party-switching election, and coincidentally right after an economic collapse.  I won’t go into epochal patterns of public impoverishment, income rigidity and inequality.  The data do show that we love to drive in traffic on trips of any major distance, but that we are learning to use other modes for trips under 3 miles.


Everything at the top of this mostly gray graph is all the trips taken by bike, walk, and transit of all types (bus, trolley, train, commuter rail, subway, light rail, automated guideway, monorail, tramway, and funicular (there are no cog railways that I know of for transit use in the US)).  Note that the gray area is the largest area in the graph, but it is declining.

Looking at median and modal (most common)distance of trip, we can see that traffic, walking, biking and transit are sorting into their optimal distances since ISTEA.


Traffic’s share of trips below 1 mile is declining, but still in the majority.  Maybe this is just a symptom of longer driveways and walks to the car?


Sarcasm aside, note that in 2009, less than 50% of the trips under a mile were by car.  17 years after ISTEA, but also a year after the worst economic collapse in living memory.  Where did those trips go?  Walking, mostly.


They only went a little bit to biking, though the pattern of bike trip distances in the table above indicates that Americans are beginning to bike more to the natural range of 3-5 miles.  In 1995, most Americans got the bike out and biked as far as the closest traffic arterial before they realized that driving a bike in this traffic was lunacy.  By 2009, bike facilities had gotten much better, so more people have been able to make much longer regular trips by bike.


Unfortunately, bikes are still a tiny fraction of the transportation, even if they are increasing.  The scale of this graph is 10% of trips, not 100%, for clarity’s sake.

My challenge is to figure out how to tease apart the effect of infrastructure from economy.  I don’t see that we have done nearly enough to truly embrace biking and walking as modes, but its encouraging to see that we are moving in the right direction.  My concern, as before, is that the right direction is the effect of economic collapse, and not policy improvement.  Biking and walking need to make a generally accepted case that they are more prosperous than traffic, not just cheaper.