Megatrend: US motor vehicle miles driven has been flat for a decade; bicycling and walking on a strong upswing

Vehicle Miles Traveled--the Federal Highway Administration's measure of how much Americans drive--has been growing steadily now for more than a century.

Since 1900, Americans have made the transition from nearly no automobiles (1900) to one car per family (1950) to more than one car per licensed drived (2000).

The result has been a continual super-growth of vehicle miles driven over the entire course of the 20th Century.

Continual super-growth of motor vehicle use has set our expectations

This continual, large growth in motor vehicle use--at two to three times the population growth--has set our expectations for everything from fuel taxes, to road and highway funding, to city planning.

Well, get ready to set those expectations on their head--because we are in a new and far different reality now--the reality where American's motor vehicle use does not grow rapidly.  

For the past decade--since the year 2002--motor vehicle miles driven has been completely flat in the U.S.

The ramifications for road and highway planning are large enough--if growth in miles traveled had continued through 2011 as it did for most of the 20th Century, today we would be looking at about 3.25 trillion miles traveled annually, about 10% more than the actual figure, which is just under 3 trillion miles.

Changing our expectations to fit the new reality

And that changes everything about road and highway planning.  Do we need more roads, more highways, more lanes?  By the last half of the twentieth century, highway engineers answered yes, yes, and yes to those questions every time--because they had learned through decades of hard experience that you couldn't build enough roads, highways, and lanes.  By they time they were built, they were full and overfull with more, more, and yet more traffic.

Now it's time to unlearn that hard-learned lesson--because traffic growth in the 21st Century is going to fall far short of expectations. We are going to find, far more often than not, that we just don't need that extra lane, that widened highway, or that minor road turned into a major road.

What it means for biking and walking

Bicycle commuter mode share in Missouri, 2000-2010
Bicycle commuter mode share in Missouri, 2000-2010

But if the ramifications for motor vehicle planning are large, the ramifications for non-motorized transportation are far larger yet.

Because when we look at the 250 billion miles that were not driven, where did they go?

Many of them--about half--became miles walked, bicycled, or traveled by transit.

In percentage terms, walking, bicycling, and transit are a very small part of Americans' miles traveled--meaning that a small percentage of motor vehicles miles traveled equals a huge percentage of the walking, bicycling, or transit miles.

Result: A small decrease in motor vehicle use equals major increase in biking, walking, and transit use.

In Missouri, for instance, in the same decade that motor vehicle use was flat, the amount of bicycling has nearly tripled (see chart, right).  Walking and transit use have seen gains, as well.

And that means we need to make a fundamental shift in our thinking and in our priorities about transportation.  To meet Americans current needs--our 21st Century needs--we need to be spending a far greater proportion of our transportation dollars on transit, bicycling, and walking, and a slightly smaller portion of our dollars on roads and highways.

This doesn't mean that cars are going away--the FHWA's charts show three trillion reasons why that won't happen soon.

But it does mean that instead of spending 90% of our transportation dollars on motor vehicles, it ought to be more like 75%--allowing us to spend twice as much as we currently do on transit, bicycling, and walking.

The long view . . .

To understand the change this will make in U.S. decision and policy making, it helps to take the long-term view.  How long has it been since motor vehicle use has been in this mega-growth phase?  

Well, I was born in the early 1960s, and the mega-growth of motor vehicle use started when my great-grandparents were in their twenties, back in about 1900. 

The graph to the right shows the growth in motor vehicle use over the course of a century--and also shows why this growth cannot continue now.  The reason is that the number of vehicle miles traveled has grown at 2-3 times the rate of U.S. population growth over the course of the entire century--and with scarcely a blip or pause at all (the two small dips in the blue portion of the curve were due to the oil shocks of the 1970s).

One result of that super-growth curve over the course of the entire 20th Century is that cities, states, and the federal government were in a continual state of catch-up--always behind in the number of paved roads and lanes needed, and always trying to stretch the dollars to catch up.

The result of that century of road building is an huge transportation network that meets the needs of motorists--but doesn't meet the needs of those who walk, bicycle, or use transit.

The transportation challenge of the 21st Century

The transportation challenge of the 20th Century was to build a multi-million mile road system, crossing the entire country and reaching every community and every neighborhood, to carry our automobiles.

The need of the 21st Century is something quite different: To fill in that road system to add everything that was neglected in our rush to catch up with that super-growth in automobile use.

That means things like sidewalks, crosswalks, pedestrian signals, bulb-outs, pedestrian refuges, bicycle lanes, bicycle routes, trails, transit stops, transit shelters.  In short, all the human-scale things that make our streets and our cities livable and truly inviting for people--and all the things that were skipped over in the rush of road building in the 20th Century.

We don't need more roads now--that battle is over and it is won.  What we need is better, more complete, more usable, more livable, more human roads, neighborhoods, and communities.  That means buildling places where our children and our grandparents--and everyone in between--feels safe and comfortable bicycling and walking, as well as driving.


Now--even after the U.S. recovers from the current economic difficulties--predictions are for miles driven to grow at most at a 1% annual rate (the rate of population growth in the U.S.).

What does this mean for road and highway planning?

Most road projects are planned using 10, 20, and 50-year traffic forecasts. Even just 10 years out, the difference between 1% and 3% annual growth rate is very large. Tw

enty years out it's a 2:1 difference.

Are we planning our roads for twice the traffic that will really exist in 20 years?

The graph to the right shows the difference between 1% and 3% annual growth in vehicle miles traveled.  The green line shows 3% growth, while the red line shows the maximum possible growth over the next 20 years, given current U.S. population trends.

The Future Isn't What it Used to Be
No one expects the number of motor vehicle miles driven to keep decreasing forever.

But a fascinating analysis by Todd Litman of the Victoria Transport Policy Institute (PDF) gives a lot of good reasons to think the amount of motor vehicle trips w

ill level off or grow far more slowly, rather than keep growing at the 2-4% annual rate they have grown for the past century.

1. Over the twentieth century, the number of automobiles in the U.S. has grown from practically none (about 1900) to one per household (about 1950) to more than one per licensed driver (2000). Growth in the number of motor vehicles just can't keep going up because there is nowhere for it to go.

American love their automobiles, but how many cars per person do we need? Or can we afford? We are close to the limit--the peak in the number of cars per capita may have been reached in 2000, according to FHWA data.

2. Future growth in motor vehicle miles traveled is likely to be proportional to population growth, around 0.9% annually, rather than the super-growth rates of 2-4% per year we saw during the 20th century. A growth rate that high simply can't continue forever.

3. The U.S. population is aging. Older citizens drive less--but walk, bicycle, and use transit more. This demographic shift will only accelerate the trends towards less driving and more walking, bicycling, and transit use.
US vehicle miles driven--a longer-term look. Source: Todd Litman, VTPI. Click for full-sized version.

We need to spend more of our resources planning and building for walking, bicycling, and transit, and less building for growth in vehicle miles traveled.

That doesn't mean bicycling, walking, and transit should get all resources and motor vehicles none! All indications are that the motor vehicle will be the dominant mode of transportation in the U.S. for a long time. And certainly it will continue to receive the majority of transportation funding.

But these trends mean we need to tilt our priorities in a somewhat different direction--a little less towards cars and a little more towards walking, bicycling, and transit.

Spending, say, 10% of transportation dollars on bicycling and walking and another 10% on transit over the next decade would quite literally transform the state of Missouri.

That is the direction the American public wants and the direction the future is going--like it or not.