For a while now I have been curious about the relative energy demands of different modes of transportation, especially bicycling and walking. Most people would agree that as a modern society we have lost touch with the environment in many ways. Food production is probably one of the most looked at areas in which this has happened but energy demands of our lifestyle are no less important.

For some context watch this video. Imagine if you had to do this every time you wanted to turn on a light. If that isn’t bad enough, imagine if you had to do this for your car’s headlights. You aren’t even moving yet and the energy demands are beyond what is humanly possible. Industrialization and reliance on fossil fuels has made us completely blind to the energy demands we make in everyday life. These are the types of orders of magnitude I have been curious about.

So I decided to do a little research and I was able to find some data on this subject. A human walking around 3 miles per hour on a level surface uses around 5 kcal/minute(1) and a bicyclist riding at ~10 miles per hour on level surface uses around 8 kcal/minute(2). These values mostly vary with speed of travel and slope. Next, I then converted MPG for an average US car and a hybrid-electric bus into BTU/mile/passenger and got the graph below.

 

BTUs Per Passenger Mile
BTUs Per Passenger Mile

 

These are obviously very rough numbers but it is easy to see the expected trend. A half full bus (29 people) uses less than half as much energy per rider as that of an average car while a packed bus uses 1/8th of  the energy per rider. The real dramatic differences though are in bicycle and walking energy use. Walking a mile is over 10 times more efficient while bicycling is almost 25 times more efficient. Even if cars become twice as efficient  (54 MPG) bicycling would still be over 12 times a efficient. Next assuming a 20-minute round trip (total of 40 minutes) and given average speed of that mode I then calculated the energy use of a trip by mode. This is reasonable because it accounts for the land uses patterns associated with each mode.

BTUs For 20-Minute Round Trip
BTUs For 20-Minute Round Trip

The first thing you should notice is that the relationship between this graph and the last graph is not linear. By accounting for land use patterns I’m able to “weigh” modes by the realistic distance they travel. Very few auto trips are 1 mile for example while most pedestrian trips are in this range. I have a hard time with orders of magnitude so look at the final graph.

One Auto Trip Equivalent
One Auto Trip Equivalent

This graph shows the number of trips by mode that can be made using the same amount of energy as a single car trip. I don’t know about you but this blows me away. Transit is a significant improvement but is no where near bicycling and walking. This is why dense walkable and bikeable cities are absolutely essential for attaining sustainability. This is just one more example of why our transportation and climate change problems are really in fact land use problems. The profound issues of sprawl and low density development are manifested most significantly in our transportation system. Transit acts as an enabler for a sustainable built environment by removing the necessity of the car and creating densities were bicycling and walking are easy and attractive.

Sources:

(1) ”Human Energy Expenditure” by R. Passmore

(2)”Influence of age, sex and body weight on the energy expenditure of bicycle riding” by William Adams

24 Replies to “Orders of Magnitude II”

  1. Interesting and good work. Electric trolley buses are approximately twice as efficient as diesel and diesel hybrid buses – would make for an even more interesting comparison. Streetcars are about the same as electric trolleys, on a per-passenger basis, depending on streetcar capacity/type.

    1. The old COMET report actually showed the streetcars being much more efficient cost-wise, though. There must have been other reasons.

  2. I would guess the average car commute takes longer than the average bike or walking trip, because biking for an hour or walking for an hour is a lot harder to do than driving for an hour.

  3. This is also why we shouldn’t be spending all our resources in streetcars where the passenger trip length is under a half mile. Walking is so much more efficient than transit. Original streetcars were built to make money and their primary competition was the human feet. Modern streetcars, trolleybuses and the like should support the pedestrian to travel further, thus helping them take advantage of the city’s jobs, services and amenities beyond comfortable walking range. Often it is said that quarter mile is that range. Streetcar and bus stops should be a quarter mile apart. Research has shown (I can cite later if you want) that pedestrians will walk further if they have a really good transit option (light rail, BRT) or if there are more destinations within walk distance. Thinking of transit as the extension of the pedestrian’s range can lead to one imagining transit as a sort of pedestrian highway network while sidewalks are the local streets. Full access in highway terms is given at the sidewalk while a bus should achieve 1/4 mile stop spacing and BRT and light rail should be closer to 1/2 or greater. If you go back in Seattle history streetcars stopped every block. Consultants in the mid 20s recommended skipping every other block. The record doesn’t indicate any massive stop removal until the 1940s when heavy transit usage required Seattle Transit to eliminate over 1,000 bus stops in order to keep buses moving. Every other block is usually about a tenth of a mile in Seattle. Still too close.

    1. I agree walking is more efficient than streetcars and that streetcars also increase the incentive to walk by increasing a person’s effective distance on foot (i.e. walk a couple of blocks, grab a streetcar for a half mile and then walk a few more blocks to get to your destination) I also agree with you about the length between stops for buses or streetcars… I am not certain about which distance would work best for each mode, but locating stops at more of a distance would improve service speeds and eliminate the costs of building and maintaining stops. Of course the distance between stops should be dictated in part by location–a downtown location might warrant more closely spaced stops to provide greater connectivity. Regarding streetcar routes, I am in favor of loop routes like the Broadway/12th Ave alternate route being proposed for the First Hill Streetcar. Loop route dissipate congestion and broaden streetcar coverage by putting more of the areas adjacent to the loop within walking range.

    2. The point I was trying to make is not that one kind of transit is better than another but that transit needs to support land use patters that create walking and bicycling opportunities. There are many ways to do this but streetcars both now and in the past were how this was accomplished. Of any mode of transit streetcars are most supportive of pedestrian speed and scale environments.

  4. When you get time…please could you extend this graph to include “typical” commuter rail, light rail, high-speed rail, ferryboats, and jet airplanes? Just to complete the picture.

    1. I wanted to but I just don’t have any idea of their energy demands. It is really easy with cars and buses because all I need is their MPG. I have no idea what that would be for LINK.

  5. I should add, I realize full well that one is extremely unlikely to walk or bike the same trip for which one would use a plane…but I’d still be interested.

  6. Bicycles and Street cars are a terrible mix. The rails are a trap for bicycle tires rendering the roads with streetcars on them non bicycle routes. Even a perpendicular crossing is risky on wet steel rails.

    Street cars and Pedestrians, that’s a win. I like the San Fransisco cable car version where you just let people hang onto the outside of the thing. Speeds up loading/unloading incredibly.

    Bicycles and cars are fine as long as the car speeds are close to the bicycle speeds. Lake Washington Blvd works pretty well. And Eugene & Berkley with the one way except for bicycle roads are exceptionally nice for bicycles.

    1. Bicycles and streetcars don’t have to be a bad mix, just look at this picture.(http://www.flickr.com/photos/ericparker/3338999659/). This preception has been caused by poor streetcar designs (here and portland) that don’t take the needs of bicyclist into account. Engineers and planners are learning and I think the next generation of streetcars will be much more bicycle supportive. It is essential that each mode supports the other mode.

      Also I don’t know about you but I don’t refer riding in mixed traffic. Yes it isn’t bad if cars are going the same speed as bicylist but that only really happens on “main street” or neighborhood streets. Lake washington blvd is much better than many streets but that isn’t were tons of people bicycle for everyday needs.

      Contraflow bicycle lanes are great and ened to be used more often.

      1. “Lake washington blvd is much better than many streets but that isn’t were tons of people bicycle for everyday needs.”

        Maybe you don’t ride during commute hours, but there are more bicycles on that road when I’m riding home than anywhere else on my route going South. Could be just people training for racing but it’s sure nice.

        Re: Photo:
        You have to be super careful crossing tracks like that when they are wet. They are almost as slick as wet leaves.

        This generation of Street cars could have been better if the city had bothered to listen to the folks who told them that Portland ran them down the middle of the street. And that was before they installed those killer tracks. I’m not hopeful that they have learned anything.

  7. Oh yeah,

    The basis of this measurement is flawed. It doesn’t matter how much BTU’s a pedestrian or a bicycle rider consumes. They are using carbon that was just in the air only a year or less ago. And they are returning it right back. Things that burn fossil fuel are returning carbon to the system that was captured millions of years ago. The recapture rate isn’t fast enough to keep up with the additional load from fossil fuel.

    1. That’s an excellent point, if you’re assuming the food we eat isn’t grown with petrochemical fertilizers. :)

      1. I’m not sure the numbers above reflect the shipping costs of food or anything like that. 5 calories / minute of walking seems to reflect simply how much energy our bodies are burning.

    2. Yes but we have obestity epidemic in this counrty and regardless how many people eat more because they go for a 20 minute bicycle ride or walk. Very few i bet.

      1. He’s saying that the carbon in plants and meat we eat was already in the atmosphere, so burning them doesn’t change the total amount of carbon above ground. Whereas with oil, we pump that carbon from underground and it raises the carbon count.

  8. I’d be interested in seeing graphs for equal distance trips rather than equal time. After all, walking out the door each day people have to get to the same spot–work, home, or where ever–regardless of which mode of transit they choose.

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