To walk or not to walk...
August 18, 2020 4:10 AM   Subscribe

Which takes more energy: riding on the tram/bus one stop vs walking 20 minutes?

I have always thought that, in theory, people should stop for cars and not the other way around as the amount of energy consumed by an idling car is more than the energy I consume by standing. That got me thinking, is it more efficient for me to walk or for me to ride on public transport?

I'm thinking of all the energy that goes into feeding me: raising animals and plants to feed those animals plus plants to feed me plus energy costs to transport it to me plus energy costs to keep food from spoiling.

My instinct is that the amount of energy used so that I can walk 20 minutes, is more than the energy cost of a tram/bus and waaaaaay more than the marginal increase in energy for me to jump on a tram/bus.

Am I thinking about this the right way? How would I go about calculating this?
posted by LizBoBiz to Science & Nature (10 answers total)
Presuming that the tram/bus will be going there anyway, you'd only be personally contributing to however much additional fuel costs to carry your weight. But it's likely a more easy calculation (and arguably more accurate) to find the per km/mile energy use for that vehicle and divide by the average passenger numbers. I found this Transport Engineering paper on energy consumption which has some good discussions and numbers including this interesting part:
The energy consumption of walking and cycling is
normally not assessed at the same way as in motor vehicle transport. In walking and
cycling only renewable energy sources are consumed; the energy consumption has
no significance in the total energy consumption of transportation. The energ y
consumption of walking is approximately 0,16 MJ/km and for cycling 0,06 MJ/km.

posted by london explorer girl at 4:18 AM on August 18, 2020 [2 favorites]

Your carbon footprint when walking partly depends on what you eat, as this article notes. More importantly, you'd also need to consider the fact that you need exercise at some point in the day for your health, so you should be burning these calories at some point anyway. It also depends on the energy used by the bus (eg, are there electric buses running on renewable electricity).

If you're thinking about this because you want to help the environment and not just as a thought exercise, the bottom line is that both public transit and walking are good choices. If you look at your total carbon footprint, there are better places to focus to make a difference (do you fly? drive? eat meat? etc).
posted by pinochiette at 4:31 AM on August 18, 2020 [1 favorite]

This article has energy usage for all sorts of transportation, which you can compare with the numbers given by london explorer girl.

E.g. some buses in Vancouver use 0.32 MJ/km per passenger when the bus is full. That's double the energy consumption of walking.

All energy is the same for physicists, but is not the same economically or in terms of climate change. If the bus is using fossil fuels, that's not good. Exactly what you eat makes a big difference, but you, unlike the gas-powered bus, can keep going using nothing but the sun's energy.
posted by zompist at 4:36 AM on August 18, 2020 [1 favorite]

Response by poster: I should mention: I'm super lazy and don't exercise at all so think of walking as energy spent in addition to normal activity. (and if this answer goes the way my instincts point, then this would be a point of argument when my friend make fun of me for being lazy when I would rather ride than walk)

Diet is not great: lots of frozen/processed foods, yes I eat meat, some fresh stuff. Though I do live in Europe, so probably slightly better environmentally than an American on the same diet.

Looking at the paper that london explorer girl linked to, it looks like they did not include fuel costs for walking, which would be part of my consideration in this thought exercise.
posted by LizBoBiz at 4:51 AM on August 18, 2020

Looking at the paper that london explorer girl linked to, it looks like they did not include fuel costs for walking, which would be part of my consideration in this thought exercise.

Unless you change your diet for walking vs. riding (there is no need to do so), the fuel costs are the same regardless of how you get around town.
posted by headnsouth at 5:04 AM on August 18, 2020 [11 favorites]

Yeah, headnsouth has it. You're not going to eat more food than you would ordinarily just for a 20 minute walk, so there would be no difference in your personal "fuel" consumption whether you walked or rode.
posted by Balthamos at 5:11 AM on August 18, 2020 [3 favorites]

How do you get into the tram? Is there a step? Steps take extra energy beyond regular walking. Do you sit down in a seat and then stand back up again? That takes more energy than walking. If you stand is it a bumpy ride? Engaging muscles to maintain balance also requires energy.

Negligible, in such a short period. But if you're in good enough physical health to walk a block the energy spent to walk a block is less than the step sit walk to seat stand walk to exit step of getting on transit.
posted by phunniemee at 6:17 AM on August 18, 2020

But hang on, is jumping on a tram really going to reduce the amount you eat? In real life terms, and for me personally, skipping out on a 20 minute walk and jumping on a tram is definitely not going to change my eating habits, so I am being exactly as energy-inefficient as if I had walked. Compare this to the choice is between walking 20 miles vs. hitchhiking the same distance -- walking that much would make me eat a lot more and increase my energy consumption (and thus my carbon footprint) significantly in a way that a 20 minute walk simply wouldn't.

By riding the tram, you may not be *greatly* increasing fuel costs for the tram but you will be *marginally* increasing them -- hauling around even your puny extra weight isn't 100% costless after all.

I say, if you're eating the same amount regardless of whether you jump on a tram or not, then it's very very slightly more more energy efficient to walk.

It gets even more complicated when you consider the long term costs of not walking. If you don't exercise, then chances are you're going to end up consuming vastly greater non-carbon-neutral medical resources later in life than if you do exercise. While a 20 minute walk every day may or may not make a *huge* difference, it might still make a small one, for example, by making it so that you remain mobile for two years longer in old age than you would if you never walked those 20 minutes every day in your youth. So, if overall efficiency is something to consider, then walking is once again much more efficient.
posted by MiraK at 6:47 AM on August 18, 2020 [4 favorites]

Best answer: This is a perfect candidate for emergy (with an "m") analysis which does a track-sum of all energy contributed to a system back to earth-based contributions.

Simply though, it would be covered mostly by:

Walking: LizBoBiz metabolic consumption + supporting energy for LizBoBiz's life in home country + slight additional metabolic consumption for walking

Tram: LizBoBiz metabolic consumption + supporting energy for LizBoBiz's life in home country + ammortized energy for the manufacturing of the tram & all components + ammortized energy for the tram infrastructure + fuel for tram + ammortized emergy of tram driver

Thumb in the air: Tram > Walking

Full Disclosure: This was very related to my dissertation topic.
posted by chiefthe at 9:49 AM on August 18, 2020 [4 favorites]

There's still energy spent walking when using a tram. You walk to the first tram stop and you walk from the last tram stop to your final destination. I would include these in any calculations. I think this is what your friends may find funny. You're still walking with both methods. The tram method just saves you a bit of walking for short trips. The tram may still be worth it to save time, during bad weather, or if the sidewalks are non-existent or poor quality.
posted by mundo at 11:55 AM on August 18, 2020

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