doug

This car versus bike ad might be relevant:
Funny Car Commercial of the Day: Maybe consider taking the bus? - Autoblog

Brent

I thought this satire was funny:

http://53x11.com/images/player.swf?t...ullscreen=true

doug

Haha.. I was gonna post the exact same thing. =)
My one is red.


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bolosky

If I understand this argument, it's that it's free with respect to carbon release to ride a bike, because riding a bike doesn't increase the amount that you're eating, it just burns it rather than turning it to fat.

I don't buy it. Say you've got a really modest 5 mile one-way commute. That's 10 miles round trip per day. Using Squint's 35 cal/mile number, that's 350 calories/day. If you commute 5 days/week, 52 weeks/year that's 91,000 cal/year. Fat's 9g/cal, so over a year you'd have to gain 10 kg = 22 lbs to store the energy that would have been used for commuting.

Americans are fat, but we're simply not gaining weight at that rate, or anything near it. So, either you're eating extra to pay for the energy of the ride, or else your metabolism is somehow slowing down (say, by lowering your body temperature) to pay for it. While there may be a little of the latter, I'm guessing that those mechanisms kick in more when you're starving than when food is plentiful. I bet that if you carefully measured it, you'd find out that you're increasing your eating to make up for the exercise more-or-less 1-for-1.

Again, recall that I never have been arguing that it's better to drive the Roadster than to bike (especially for me since I ride an exercise bike pretty regularly). Rather, I'm just trying to figure out the relative carbon footprint of the two, and I was surprised that it came out so close. I still think it is probably within a factor of 2 (or, as someone pointed out, a win for the Roadster if you carpool). Also, while I haven't worked out the numbers, I'd guess that neither of them can touch the efficiency of riding a bus, not to mention an electric powered train. Which, in turn, can't compete with just living closer to work (or dying, which really reduces your consumption!)

Brent

Right. How do you solve a problem like Oprah?

This is where I trot out the fuzzy math and unsolved problems of why we gain or lose weight and then throw up my hands. But keep in mind that 350 calories is about one Starbucks muffin...

doug

Don't worry, I appreciate that.

Or more of it ends up in the toilet. Just saying human physiology makes a total environmental impact comparison a bit more complicated. People who exercise regularly burn more rest calories, so they may need to consume more even if they're not biking to work. Yet a heavier person has to spend more energy going up a flight of stairs (if she/he is so inclined).

Practically speaking, the type who bikes to work is probably health conscious and that energy spent commuting likely displaces energy that would otherwise be spent in the gym.

In the end, the purpose of such a calculation should be as a guide for behavior while the goal for most people should be a long and healthy life while reducing environmental impact.

MPT

Well, given how efficient cycling is over walking, I certainly have a solid argument now as to why I should take my Tesla over the road at lunchtime rather than walking across in the rain.

felix the cat

Thanks for your post, bolosky, I appreciate, how efficient the electric transportation is, including the Tesla Roadster.

An order of magnitude more efficient is my electric scooter, with only 3.5kWh/100km, translated in american measures: 3.5kWh/60miles, or 60 Wh/mile! And is also can carry two persons, which equals 30Wh/mile per person, assuming a "scooter-pooling" system!

raymond

To be fair you might want to compare the two modes of transportation as equal speed. A Tesla at 20mph consumes approx. 130 Wh/mile.

Cycling 30mph really does take more energy than a lazy 10mph, not to mention cycling (level!) at 50mph!

Brent

A couple of more issues to consider:

1) A driver consumes calories at a higher rate than, say, a couch potato. The 190-pound driver might go through 100 calories per hour or more. Race car drivers expend upwards of 350 calories per hour.

2) The coefficient of drag for a bicyclist on a UCI-approved (i.e., "normal") bicycle is about 0.9. The Roadster comes in around 0.35. (A fully enclosed bicycle/tricycle (Sinner Mango) presumably has a better coefficient, although I can't seem to locate a number.) However, rolling resistance has to be less on a bicycle.