Transit and walking are time consuming. Most people are just too busy. That’s obvious, right?

Well, as my family begins the ninth week of its experimentin car-less living, I’m finding a few flaws in that logic. Here are two.

1. Time spent on transit is different from time spent driving. People vary, of course, but for me, transit time is a pure gain over driving. I don’t enjoy driving. I’d rather read than listen to music or talk radio. And I can read without queasiness on all forms of transit. For me, then, car time is a waste of life, but transit time is living, and I’ll happily choose a 30 minute transit trip over a 15 minute car trip. For me, driving is time consuming.

2. Just so, walking doesn’t consume time, for different reasons. In fact, walking creates time. For one thing, if you walk for transportation, you don’t have to go to the gym as often.

More profoundly, walking gives you time you wouldn’t otherwise have at all. Walking makes you live longer, as Clark posted here. The largest ever study of the subject found that walking 30 minutes a day, five days a week, adds 1.3-1.5 years to your life, on average. (More vigorous exercise adds even more.) On reasonable assumptions (detailed below the fold), this relationship means that for every minute you spend walking, you get three back.

Time spent walking, then, is utterly free. It’s time you would have spent dead.

Nowadays, when I’m walking, I get a little pleasure in the thought that I’m cheating death, that every minute I spend afoot is an extra moment of life.

Boring, wonky, calculation notes:

My assumptions—which I’d appreciate some astute blog reader checking against the original journal article that reports the study on which Clark posted—are that you have to walk 30 minutes a day, five days a week, for thirty years to get the 1.3-1.5 year lifespan bonus. I made up the 30 year figure (too busy to read the journal (wink)).

Then I calculate 30 minutes x 5 (days) x 52 (weeks) = 7,800 minutes of exercise per year x (guess of) 30 years = 234,000 minutes of walking, repaid with 1.4 years or 736,000 minutes of added life. That’s about three minutes extra for every minute you walk.

Note that even if have to walk five days a week from birth to age 90, you’re still getting every single walking minute back, though you wouldn’t get three.