[streptomycin]

Orders of magnitude? Doubt it. Check out http://bicycleuniverse.info/transpo/energy.html - while biking is typically more efficient than driving, it's not orders of magnitude. If you play with their calculator, you can find that driving a 50 mpg car and riding a bike really fast both have about the same carbon emissions. This is just from factoring in increased food consumption.

[colin_mccabe]

Thanks for sharing that link. It's interesting to think about this. I don't agree with the conclusions, though.

First of all, your metabolism isn't going to stop (assuming you're still alive), so it's not really fair to say that those calories you burned wouldn't have been burned if you hadn't biked. I exercise a few times every week. If I bike less, I just have to do more exercise, but i burn about the same number of calories.

Secondly, most bike trips are short and relatively low speed. Biking encourages you to explore your local area. Lower speeds mean lower wind resistances, and shorter trips obviously make the mileage considerations a lot less important. I really don't think I'd be willing to travel more than a few miles by mike, since I don't want to spend hours in transit.

[moheeb]

Your link doesn't mention the resources used in the production of either a bike or a car.