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Bikes are more efficient than walking, but that's only because roads are flat so wheels make sense, right?

Does it make sense to say that this fact is simply gained by putting a lot of energy into making the earth flat, into making tarmac and putting it there?

sammy gerbil
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scrrr
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  • Bikes are not only more efficient because earth is flat. They're efficient because the ratio $\text{energy spent}/\text{speed or distance travelled}$ is usually larger for someone riding a bike than for someone walking. I'm unable to link why would bike efficiency be justified by the mayor building a cycleway. – QuantumBrick Jun 28 '16 at 11:20
  • Physically, your comparison makes no sense at all. The reduced energy loss of cycling compared to walking has nothing to do with the energy it costs to build a road. However, if you were to plan to build a bicycle path/road/railway, than this is exactly the sort of reasoning you should apply in deciding whether it is useful to invest the energy in building the infrastructure – Crimson Jun 28 '16 at 11:54
  • As an on-face economics argument you probably have it right, the energy needed for road construction will probably not be returned in the energy savings of cycling vs. walking, however, the modern bike design is an immediate consequence of the flatness of available roads. If no flat roads were available, we would be designing these machines differently to begin with, which shows you one of the pitfalls of on-face economics. – CuriousOne Jun 28 '16 at 11:55
  • I'm voting to close this question as off-topic because this is an economics and not a physics question. – CuriousOne Jun 28 '16 at 11:56
  • No, wrong: cycling is more efficient than walking because walking is not very efficient. Cycling up a hill is almost always more efficient (but typically requires higher sustained power output) than walking up it. –  Jun 28 '16 at 13:07

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What you are saying does make sense, and ties in with some of the points made in What makes running so much less energy-efficient than bicycling? Although you mention "putting a lot of energy into making the Earth flat", I do not think you are making an economic argument. You are merely asking if the superior efficiency of cycling is due to the fact that we have flat roads to cycle on.

Yes, cycling on roads is more efficient than walking on them because tarmac roads and bicycles (or cars) have been designed to work well together to make an efficient system of transport. Efficiency is only one criterion : cost, comfort and flexibility are some others.

Energy is lost in cycling mainly because of rolling resistance, due to the deformation of the tire. If roads and wheels were made of hard steel, and roads were perfectly smooth and flat, the efficiency of cycling would be even higher because the deformation would be far less - though much less comfortable if there is even the slightest bump.

Going up hills, the bicycle loses some of its advantage because you have to do extra work to raise the bike (7-20kg) against gravity, as well as yourself (around 70kg).

Cycling over rough ground (using a bike designed for roads) can be less efficient than walking over the same ground. In the extreme, cycling through a boulder-field is almost impossible, even on a mountain bike, whereas with practice and good balance it is relatively easy to step from one boulder to the next.

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