Bicycles are wayyy more efficient than walking. I have even heard it is the most efficient transportation available to humans although I can’t confirm that. The reason is simple: wheels. Wheels let you take advantage of Newton’s law of motion that says that an object in motion will tend to stay in motion. On a flat road, you start a bicycle in motion and all you have to input after that is energy to compensate for wind resistance and mechanical drag (which is pretty low. This principle even applies on hills and you get the energy back when you coast downhill. Your body and legs don’t take good advantage of inertia. You have to move your legs one after the other no matter what and even going downhill takes work.
The combination of wheels - which are so great for moving around for the reasons Shagnasty has explained - and gear ratios that allow a small amount of leg movement to be translated into a large amount of forward motion make bicycling very efficient.
The reason bicycles are often called the most efficient means of human transportation is that you get more travel distance per unit of energy input than any other means of transportation ever devised (well… the Voyager spacecraft might actually win here, so let’s remember that we’re talking about terrestrial transit). I believe Howstuffworks.com had a segment on how many miles per gallon a person on a bicycle would get if he or she could drink gasoline. It turned out to be in the ballpark of 900 miles per gallon!
This topic has come up a couple of times on the board recently, and in one case there ensued a discussion about what “efficient” means. In this case, it means the energy required to move a human around. (Some people argue that the energy per pound is more efficient for a car, but then you have to move the car, too. Others mention that a human being isn’t especially efficient, lots of waste heat. And so on.)
A couple of reasons:
[li]Muscles get tired just holding something up, even when it’s not doing actual work. If you crouch down slightly and hold that position, for example, you’re not actually doing useful work. But your legs still get tired. There’s a lot of that going on while walking.[/li][li]Walking involves moving your body up and down repeatedly, and this is actual work.[/li][/ul]
On a bicycle there’s much less wasted motion, and you are sitting down, which is less tiring than standing/walking.
Wait a minute, I find it very difficult to go up a steep hill on a bicycle and if the hill is steep enough I’ll end up having to get off the bicycle and walk it up the hill. I find the walking up the hill to be much easier.
Please explain “This principle even applies on hills”.
As a full time pedalist (don’t own a car), I have to agree there’s a lot to bienville’s objection. The problem is the converse of what makes a bike easier in general: the wheels. On a hill, you have to fight gravity continuously just to hold your position, plus an increment to gain elevation. Having done a lot of this, I’ve had occasion to do the math. In general, one spends about four times as much time climbing as one does descending. So, you get the potential energy back, but from an energy-expended perspective, you don’t really. That said, I find pedaling a hill easier than walking, but it’s not a blow-out.
Bicycles are in their element at speeds greater than walking. It isn’t too hard to picture a long shallow downhill followed by a long shallow uphill. Inertia from the downhill portion will help on the next uphill. Even when you are peddling on the uphill part, you are using inertia to your advantage.
However, you are correct in some ways. Legs are superior to many applications and millions of years of evolution have made them superior to anything else for harsher terrain in terms of general usability. Legs can be used on almost any terrain. Bicycles have a hard time on steep uphills because the unusual application of our muscles force us to go slowly and pedalling becomes inefficient at that point. Legs are built to be most efficient at those speeds and conditions.
I disagree. A man walking up a hill has to do the same too; that really isn’t a disadvantage of bicycles.
Walking up a hill is easier than riding a bike up that same hill, but the main reason is that walking is slower. Given the same efficiency, of course it’s twice as hard to bike up a hill at 6mph than to walk up at 3mph. Riding the bike at 3mph would be equally easy, except it can be difficult to balance the bike at that speed.
Another reason is that most bikes sold today have very high gearing, especially road bikes. And even if it does have low gears, many riders don’t use it properly. If the gearing isn’t low enough, riding up a hill requires a very low cadence (pedal RPM), where human legs aren’t very efficient. Our muscles are similar to gasoline engines in that sense - a car won’t be very efficient if you force it to climb a steep hill in 4th gear.
It’s also a matter of technique and fitness. For the most part, I can ride up any paved street on my road bike faster than I can walk, except in a few extreme cases. There is technique to riding up hills, you get out of the saddle, you attack, you shift at the right time, and you put out more power for the time it takes.
But at some point, the gearing and angles consipre against you and walking makes sense. What that angle is varies for different people, a TdF rider can power up a very steep hill and not break cadence.
I you’re saying this, you’re going up a hill for which your bike is not geared properly for a person with your weight and level of physical fitness.
I’d venture that half of the bicyclists out there don’t have proper gearing for hillclimbing in their neighborhoods.
What all three of you are neglecting to consider (it appears) is friction. When walking, friction between your feet (i.e., usually, your shoes) and the pavement holds you on the hill with little or no effort. Whereas, when pedaling, the bike wants to roll back down the hill. How powerful is that force is indicated by what happens when you crest the hill and begin the descent. And, of course, if you average the effort for both stages, pedaling wins hands down. But that’s not particularly relevant to bienville’s point.
BTW, my bike is geared quite low. After all, I live in a city with lots of hills.
But if you do a track stand, then you are stationary (just as you would be if you were standing on the hill) and not using any energy climbing, and not rolling back either.
It’s been covered above, but I just wanted to drop in and emphasize that biking up a hill is generally more efficient than walking. However, as been pointed out, if one can’t go up fast enough to keep from falling/tipping over or losing traction on the back tire or wheely-ing over backwards, then biking isn’t an option. For example, in off-road riding there may come a point where it is faster to hop off and push the bike - the energy expenditure is very high for this if you want to move briskly, but it’s faster than pedalling, just because riding at very low speeds, low cadences, and steep pitches is inefficient.
For example, riding a tandem off-road with my 7-year-old daughter, we’ve come to spots where we are traction limited - low weight over the rear tire, but still high overall “vehicle” weight. Walking at that point is all that works, but it’s much slower than riding, and we hop on the next chance we get. I could believe that there comes a point where there is a cross-over in efficiency between walking/running and bicycling - or at the least a cross-over in terms of maximal sustainable climb rate.
Frankly, I don’t understand why I have to fight so hard for such an obvious principle. Yes, a track-stand is possible,but it isn’t free. On the contrary, it takes a lot of effort, on a hill a lot of effort. Also, it doesn’t get you up the hill. Yes, you can keep yourself from rolliing down the hill by applying brake, but that also keeps you from moving forward. Obviously tyres have friction; they also obviously have ball bearings.
Let’s take as an example a fairly typical case. Suppose we want to climb Telegraph Hill here in SF. (It’s the one on top of which Coit Tower sits.) That’s a hill of about 300 feet (100 meters). In climbing this hill, we have to overcome three things. First is forward motion. That’s trivial; maybe half a mile, and we’ll be going too slowly for wind resistance to matter much. Second is elevation, we have to climb those 300 feet. Third, we have to resist the tendency of the bike to roll back down the hill. Of those three, what do you guys think would be the allocation of effort? Based on my experiece and the difference in speed among level, uphill and downhill, I would estimate the allocation at something like 5% for the forward motion, 20% for the elevation and 75% for resisting gravity. Where would ya’ll put the split?