What's your Thoreau speed?

In Walden, Thoreau proposed a modification of the traditional formula for calculating speed. Instead of merely dividing the distance traveled by the time it took to cross it, Thoreau proposed reckoning also the cost of the ticket. Imagine, he writes, that he and a friend both want to go from Concord to Fitchburg.

I say to my friend, Suppose we try who will get there first. The distance is thirty miles; the fare ninety cents. That is almost a day's wages. I remember when wages were sixty cents a day for laborers on this very road. Well, I start now on foot, and get there before night; I have traveled at that rate by the week together. You will in the mean while have earned your fare, and arrive there some time to-morrow, or possibly this evening, if you are lucky enough to get a job in season. Instead of going to Fitchburg, you will be working here the greater part of the day. And so, if the railroad reached round the world, I think that I should keep ahead of you; and as for seeing the country and getting experience of that kind, I should have to cut your acquaintance altogether.

The thought experiment provided the donnée for a children's book published in 2000, Henry Hikes to Fitchburg, by D. B. Johnson.

There's no reason to distrust Thoreau's math. A healthy adult could walk thirty miles in a day. According to a 2007 study, people in cities walk in the range of 3 and 4 miles per hour. Thirty miles is a long day's walk, but it's feasible. Nonetheless, I remember that when I first read this passage in Walden, I admired the cleverness but didn't think it could possibly be true nowadays. After all, in a week I could earn the fare for an airplane ticket that would take me to California, and I couldn't walk there in a month, I don't imagine. (I made this innumerate estimate, of course, long before the price of oil skyrocketed, taking airplane fares with it.)

Lately I've started to wonder about cars, though. I have a new bike, and it seems quite often that cars make a great show of passing me, only to have me catch up at the next stop light. (When I bike in the city, I wait at stop lights, by the way, so this isn't about the bonus that accrues to outlaws.) When driving, too, now that I'm bike-conscious, I've noticed that we may pass a biker in Manhattan, only to have him pass us when we get off the expressway in Brooklyn. Do cars actually reach their destinations faster than bikes? And even if the simple speed of cars is higher, is what we might call their Thoreau speed higher?

The concept of Thoreau speed was reprised in the social critic Ivan Illich's 1974 book Energy and Equity, a critique of transportation. Illich writes that

The typical American male devotes more than 1,600 hours a year to his car. He sits in it while it goes and while it stands idling. He parks it and searches for it. He earns the money to put down on it and to meet the monthly instalments. He works to pay for petrol, tolls, insurance, taxes and tickets. He spends four of his sixteen waking hours on the road or gathering his resources for it. And this figure does not take into account the time consumed by other activities dictated by transport: time spent in hospitals, traffic courts and garages; time spent watching automobile commercials or attending consumer education meetings to improve the quality of the next buy. The model American puts in 1,600 hours to get 7,500 miles: less than five miles per hour. In countries deprived of a transportation industry, people manage to do the same, walking wherever they want to go, and they allocate only three to eight per cent of their society's time budget to traffic instead of 28 per cent.

Unlike Thoreau's numbers, Illich's aren't the sort you can look up on a railroad timetable or check against your own pedometer, and Illich doesn't give his sources. So I was skeptical of his algebra, too, when I read it. But there is an awful lot of high-quality data readily available on the internet. . . .

According to Pat S. Hsu and Timothy R. Reuscher, Summary of Travel Trends: 2001 National Household Travel Survey (U.S. Department of Transportation, Federal Highway Administration, December 2004), in 2001, the most recent year whose statistics are available, the average length of a weekday trip in a vehicle was 9.75 miles and a weekend trip 10.22 miles. The average time spent driving on a weekday trip was 64.79 minutes, and on a weekend trip 52.39 minutes. That means that the average speed on weekdays was 9.02 miles per hour and on weekends 11.70 miles per hour.

Right away, then, it's apparent that the simple speed of cars is about that of bikes. It's higher than that of walkers, but only by a factor of three or four.

Now what happens if you add in the time it takes to earn the cost of the ride, as Thoreau and Illich think you ought to? According to the Federal Highway Administration, the average annual miles driven by a vehicle in 2001 was 11,078. According to Your Driving Costs: How Much Are You Really Paying to Drive? (AAA, 2008), estimates of the average cost per mile of driving a car vary according to annual total mileage and the size of the vehicle, but for an average-size sedan (i.e., not an SUV or a minivan) that goes 10,000 miles a year, the average per-mile cost is 71.0 cents. This is an awfully convenient statistic for our purposes. Since this AAA number includes fuel, maintenance, tires, insurance, license, registration, taxes, depreciation ("the difference between new-vehicle purchase price and estimated trade-in value at the end of five years"), and financing charges, there's no need to fiddle around trying to research gas prices or the actual cost of buying a car. Returning to the average trips from the Federal Highway Administration, it now appears that the cost of an average weekday trip is $6.92 and of a weekend trip $7.26.

According to the Bureau of Labor Statistics, the average hourly wage of an American in 2005 was $18.62. (I realize I'm using driving statistics from 2001, cost-of-driving statistics from 2008, and wage statistics from 2005, but in each case these are the most recent numbers I could find. Sorry!) Therefore, on average, the cost of a weekday car trip sets an American wage-earner back 22.3 minutes, and a weekend trip sets him back 23.4 minutes. From here it's easy to recalculate the speed of those trips including the time it takes to earn the cost of taking them. The Thoreau speed of an average trip is 6.72 miles per hour on weekdays, and 8.09 miles per hour on weekends.

So the Thoreau speed of a car exceeds the speed of walking by only a factor of two. If hidden costs of cars such as car-related injury, death, pollution, and global warming were included, it might well be a tie.

At this point in my calculations, I Googled to find out the average speed of bicycles, and I discovered, serendipitously, that I'm not the first person to try to do this math. What's more, I'm not even the first person to invoke Thoreau and Illich while doing so; someone named Brad Morgan invoked them in 1991. And a fellow named Ken Kifer has made a much more thorough assessment of the costs of driving. Kifer has also assessed the costs and the Thoreau speed of bicycles, into the bargain. He estimates the Thoreau speed of cars as between 4.8 and 14.4 miles per hour, and the Thoreau speed of bicycles as between 8.9 and 14.8 miles per hour. Though beaten to the punch, I'm posting anyway, because my sources and method are different yet I end up confirming Kifer's conclusion: When costs are factored in, cars are not faster than bikes and only twice as fast as walking.

Comments

[Charles P]

Very persuasive. But here's a better law, re stoplights:

http://www3.state.id.us/cgi-bin/newidst?sctid=490070020.K

[Milan]

That is very interesting.

I am curious how this works out interpreted in two different ways. In the first, you ignore the capital costs of the car and bike and look only at operating expenses. In the second, you factor them in in both cases.

I expect that the first would make the car look better relative to the bike than the second.

[ZBicyclist]

Ken Kifer would be pleased and complimented that you have quoted him.

Ken was unfortunately killed by a drunk driver a few years ago. His web pages are still there, because they still contain information of value.

to Milan: the AAA figures cited DON'T ignore the capital cost of the car -- that's factored in as depreciation.