Bike vs. Drive

I calculated that a roundtrip from East Nashville to campus (about 5.5 miles each way) currently costs me about $1.75 in gas money. So last night I dragged the bike trailer out of the shed. My bike doesn’t have a predrilled hole to connect it to the trailer, so I just used the rear wheel skewer. (I hope this is safe. If anyone has an opinion, please let me know). It felt pretty solid. I took Carter out after dinner to beta test our bike + trailer concept.

Things went great, so this morning I piled Carter, my gym bag, and my computer bag in the trailer and headed toward the pedestrian bridge. All told, I think I was towing about 60 or 70 pounds, but it really didn’t feel like it (except perhaps coming uphill on Demonbreun). The trip by bike is only 4 miles, and I was able to make it to his daycare in 25 minutes. By car, it takes me closer to 10 minutes, but then I have to drive to a parking space (5 minutes) and walk back in to campus (10 minutes). Granted, I had to take some time to lock the bike and then change clothes, which put my total time from doorstep to office (not counting time inside the daycare, which is the same whether I bike or drive) at about 35 minutes.

That said, by biking I am able to double-task—my commute is also my exercise time. Thus, one could say that I gain an additional 50 minutes.

It looks as if I gain $1.75 in gas costs by extending my commute time by 10 minutes each way. I also burn roughly 220 more calories. However, I’m not trying to lose weight, so should I include the cost of additional food to replace these calories? Food is indeed a kind of fuel. If so, let’s say I spend about $1.00 on a cliff bar, muffin, or fruit. This means that the true cost savings may be closer to $0.75.

I can think of ways to make this cost-benefit calculation much more precise (and thus much more complex). The real cost of driving to work is considerably higher. The more I drive, the more the car depreciates and the more routine maintenance I have to perform. Further, once we look at the societal costs of driving vs. eating more, things get really controversial.
But I have comps next week, and I should probably start doing some real work.