ego.istic.org

Gary Rides Bikes today pointed me to a miles per gallon calculator for cyclists. The eponymous Mr. Kavanagh is proud of his 696mpg, and a female commenter was pleased with her 739mpg (girls being lighter, thus less energy-intensive to move). Thus tempted, and already curious to find the weight of my bike, I took my bathroom scales outside to try it.

The total weight of bike + rider is 86kg (of which 15kg is the bike, me not having had my tea yet). This is me in a T-shirt and shorts, not my heavy Winter gear. The weight of the bike includes all the fittings and the lock but excludes the pannier bags, lights, change of clothes, sunglasses case, groceries, books, and other heavy junk I normally travel with. (See this comic if you can sympathise with that kind of thing.)

GNU units tells me that that's about 190lb. My cruising speed in still air is about 20mph. (Yes, I know that's quite fast. Yes, I have measured it.) Put these into the calculator, and out pops the figure: 529mpg. This is ridiculously low!

In this time of carbon footprints and emissions, many cycling campaigners are quick to point out the environmental benefits of replacing driving with cycling. The defensive response from the motoring lobby is usually to call the benefits into question, and it's easy to do so with this bit of fun. It's a completely inaccurate calculation, makes too many simplifying assumptions, ignores the effects of accelerating and braking (something you often have to do in towns), and uses a questionable formula to start with. In particular, it's interesting how putting in the same numbers given in the Wikipedia article it links gets you almost twice the power.

For me, it really is just a bit of fun, and an excuse to bemuse my neighbours slightly. The environmental benefits of cycling are much less important than the social benefits of reduced congestion and safer streets, and even these are less important (to me, anyway) than the simple fact that it's more pleasant, even when it's raining.