
Walking a mile is 3x more expensive than driving, from a fuel perspective - qvorak
http://www.datadriventhoughts.com/2016/08/08/walking-is-3-times-more-expensive-than-driving-from-an-energy-perspective/
======
honkhonkpants
This analysis makes the same mistake that innumerable other analysts have made
before: that going a mile is something worth doing. If you stipulate that
everything is a mile apart, then you're guaranteed to get this outcome.

The point of walking is that if you throw out the cars then everything is much
closer together, and then you don't have to walk a mile. If I start from the
Ferry Building in San Francisco and walk a mile up Sacramento street, I'll
pass thousands of establishments of all kinds. If I start at the Ponte Vecchio
in Florence and walk a mile I will pass literally every single thing there is
in the old city. In a walkable city you'd never need to walk a mile, so
finding out what is the most energy efficient mode of going a mile is
relatively pointless. What you actually need to know is the most energy
efficient form of building, not the of transport.

~~~
prodigal_erik
How many Ethiopian restaurants, improv theaters, and dueling piano bars did
you pass? A lot of niche interests can't sustain themselves at all with only a
small fraction of a small population.

~~~
honkhonkpants
Well you got me on the piano bars but as far as Ethiopian food goes there are
dozens in my relatively walkable city and I just spot-checked the first car-
choked blasted expanse that came to mind (Phoenix) and there are only five in
a much larger metro area.

If I was an Ethiopian restaurant owner would I prefer a restaurant in a dense
neighborhood with five families living in apartments right on top of me, or
would I prefer to be in a strip mall at the corner of an American suburb with
nobody in walking distance and only a few hundred families within a mile? I
know which one I'd want.

~~~
prodigal_erik
Odd, are you in a destination for Ethiopian immigrants? I would have expected
something more like the single restaurant serving the entire Napa valley. Most
people don't even know Ethiopia has a cuisine, much less seek it out.

~~~
honkhonkpants
Yes we have many Ethiopian and Eritrean immigrants in Oakland and Berkeley.

------
socialist_coder
This should not really be very surprising as walking is not very efficient.
You should be comparing driving to cycling, as both are wheeled forms of
transportation. Cycling is up to 5x more efficient than walking
([https://www.exploratorium.edu/cycling/humanpower1.html](https://www.exploratorium.edu/cycling/humanpower1.html))

So, if you compare driving to cycling, cycling wins hands down. And, this is
with the artificially low cost of fossil fuels. If fossil fuels properly
factored in all the environmental damage, cycling's efficiency advantage would
be even higher.

~~~
thaumasiotes
> Cycling is up to 5x more efficient than walking

"Up to" doesn't mean much. Biking is explicitly considered in the original
piece:

> Surprisingly, from a pure energy perspective (using the methodology
> mentioned above), biking, walking, and running are the three most expensive
> types of transportation listed

~~~
seiferteric
Does it consider the health benefits and therefore reduced medical costs we
would have if more people walked/biked?

~~~
Nullabillity
Those people will probably more than make up for those costs later in life.

------
knowtheory
Except your food expenditures are a sunk cost, and you can't replace them with
fuel expenditures.

This is literally comparing apples and gasoline.

~~~
thaumasiotes
Your food expenditures vary with the amount of work you do, no different than
your car's fuel expenditures. They are most certainly not a sunk cost for this
purpose.

~~~
sfifs
Actually not so much surprisingly - the key exceptions being if you are
working in very cold climates where the body has to generate more heat to keep
you alive or you're training competitively for very physically sports.

It turns out that about 70-80℅ of what most people consume goes into simply
keeping them alive (research basal metabolic rate & daily calorific
requirement) and the impact of "work you do" is only a small variation - with
the above exceptions.

Also interestingly (unable to search the paper reference on phone) there is
research that shows that dramatically different lifestyles like Namib desert
nomadic hunter-gatherer vs. typical urban don't actually differ on metabolic
rates (accounting for non-fat weight)

~~~
allendoerfer
You should have posted that at the top level, so this could be the top
comment. While the statistics are nice to look at, I have read the article you
mentioned, too (was on HN a while ago) and instantly thought that metabolism
unfortunately renders the whole calculation useless and wrong.

~~~
thaumasiotes
> While the statistics are nice to look at, I have read the article you
> mentioned, too (was on HN a while ago) and instantly thought that metabolism
> unfortunately renders the whole calculation useless and wrong.

Why did you think this? Can you articulate a change that metabolism would make
to the calculation?

~~~
allendoerfer
It adapts, like my parent comment has said. Most of our energy is spend on
keeping the system running, not running with our feet. If we start to run, we
burn more energy, because our metabolism has not adapted yet, once it adapts
(see his example with Africa), there is very little change. Obviously this is
simplified.

~~~
thaumasiotes
Are you claiming that running requires no more energy than sitting? If not,
what are you trying to say?

The energy that you need to spend on overhead doesn't go down because you
start running.

~~~
allendoerfer
I am claiming that there is no linear relationship between the amount of
running and burned calories.

~~~
thaumasiotes
So what? If you propose to have someone do some amount of running that they
wouldn't otherwise have done, they must pay for that running in one of two
ways:

1: Eat more. This has a linear relationship to the amount of additional
running.

2: Do less. By doing less, you can redirect calories that would have been
burned anyway to the task of running. You cannot, by definition, redirect
calories that are budgeted for the basal metabolic rate.

By paying for the extra running "in kind", by not doing activities you would
otherwise have done, it is easy to show a nonlinear relationship between
"total running done" and "total calories expended". But that's spurious, it
has nothing to do with the energy cost of running. There is a linear
relationship between "total running done" and "total calories expended on
running", and that is what matters when calculating the cost of running.

~~~
allendoerfer
Unless one does this every day, the metabolism adapts and one now does not
need to eat more (or significantly less "more").

The correlation is not that simple as you make it sound.

Edit: To anticipate your next answer: If you run more on top of that, yes, you
have to add additional calories somehow and the process starts again. The
point is that a car does not have this mechanism at all so it does not make
that much sense to compare them like equals.

~~~
thaumasiotes
> Unless one does this every day, the metabolism adapts and one now does not
> need to eat more

Why would there be more adaptation to something that occurs rarely than to
something that occurs often?

You appear to be describing the following sort of situation:

BEFORE: 100 units of energy expended / day, of which 70 are the rest
requirement and 30 go to discretionary activity. This means that 100 units of
energy are consumed per day.

THE CHANGE: discretionary activity increases 20%, leading to 106 units of
energy expended / day and food intake of 106 units of metabolizable energy /
day.

AFTER: discretionary activity stays constant, but "metabolic adaptation" kicks
in, reducing energy expenditure back to 100 units / day. Or, "metabolic
adaptation" kicks in, causing a diet that had provided 100 units of energy per
day before to provide 106 units / day after.

This doesn't happen, and metabolism is not capable of "adapting" in either of
those ways. It is capable of adapting by burning more or less mass per unit
time, but you can't burn what isn't there. A person's physical structure may
change, which changes the efficiency of various activities (though see
below!), and their basal metabolic rate, but that is not a metabolic
phenomenon. An elevated level of energy expenditure means an elevated level of
food intake.

I have found the paper I assume you're talking about,
[http://journals.plos.org/plosone/article?id=10.1371/journal....](http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0040503)
"Hunter-Gatherer Energetics and Human Obesity". First I'll note that it does
not investigate, or discuss, caloric intake at all. Fortunately, we know that
for a person who is not gaining or losing weight, caloric intake is equal to
energy expenditure. It documents that the Hadza, a group of hunter-gatherers
in Tanzania, have the same daily total energy expenditure as other populations
elsewhere in the world, except farmers (who have higher energy expenditure).
It _specifically_ documents that the energy cost of walking is the same for
the Hadza as it is for everyone else:

> comparisons of activities common across cultures do not indicate that Hadza
> muscle and locomotor physiology [are] inherently more efficient. The energy
> cost of walking (kCal kg^{−1} m^{−1}) for Hadza adults was well within the
> range of values reported for Western subjects: of 20 U.S and European
> populations included in a recent meta-analysis of treadmill walking cost, 14
> had mean [minimum cost of travel] values below the Hadza mean. [Resting
> metabolic rate] for Hadza adults measured while sitting averaged 11% above
> predicted BMR, within the range of values (7–35%) reported for other
> populations.

It documents that the Hadza have much higher physical activity levels than
Westerners. Since physical activity is just as energetically costly to them as
it is to us, this requires that their basal metabolic rate be much lower than
ours, and it is -- because they are much smaller than we are:

> Regressing [total energy expenditure] on estimated [basal metabolic rate]
> suggests that group differences in [physical activity level] were related to
> differences in body size, as the Hadza are significantly smaller than their
> Western counterparts. In a multivariate analysis controlling for age and
> sex, the relationship between TEE and estimated BMR did not differ between
> Hadza and Western subjects. However, because TEE is correlated with
> estimated BMR with a slope <1.0, PAL (the ratio of TEE/BMR) tends to be
> greater among smaller individuals; this is particularly evident among men in
> our sample.

It documents that traveling, being pregnant, and lactating are all
uncorrelated with daily energy expenditures, despite being very energetically
expensive. Given this, it speculates:

> We hypothesize that [total energy expenditure] may be a relatively stable,
> constrained physiological trait for the human species, more a product of our
> common genetic inheritance than our diverse lifestyles.

This means that when Hadza have to do extra work, they overwhelmingly pay for
it by doing less elsewhere rather than eating more. That means that the cost
of traveling is actually much higher than it would appear just by looking at
the energy requirements -- eating extra food is easy, but empirically you are
much more likely to pay for traveling by failing to accomplish things that you
otherwise would have done. I don't find that reassuring.

IN SUMMARY:

\- Hunter-gatherers meet the high energy requirements of their lifestyle by
being physically small, which lowers their basal metabolic rate. This strategy
is not open to someone deciding whether to walk or drive; they are already the
size they are.

\- Hunter-gatherers are no more efficient at walking than anyone else,
regardless of your several previous comments. No amount of habituation will
lower the energy cost of walking (or running, etc.).

\- Empirically, energy you spend on running is likely to be made up by failing
to do something else that you would otherwise have done. This cost, where it
applies, is probably significantly higher than the energy cost. (On the other
hand, this result is from a group of hunter-gatherers who aren't necessarily
able to eat additional food even if they'd like to.)

~~~
allendoerfer
My wording was unclear, should have been:

Unless one ALREADY does this every day (because then the metabolism already
would have adapted) …

~~~
thaumasiotes
But that is not true; metabolism does not and cannot adapt in the manner you
suggest.

------
rezashirazian
The data also ignores the fact that walking leads to a healthier lifestyle
which means living longer, which is more costly than not living longer.

~~~
TheSpiceIsLife
Yes, and one should also account for the reduced tax burden of dying younger.

~~~
jogjayr
But then you also have to account for the reduced earning potential due to
dying younger :P

~~~
Nullabillity
Not really. If you die at 70 rather than 90 then your total earnings were
probably pretty much the same.

~~~
TheSpiceIsLife
In Australia those additional 20 years on the current full rate pension for a
single person represent an additional AU$454,428.00 of income[1].

1\. The full rate includes the supplements for a total of $873.90 per
fortnight for a single person as per
[https://www.humanservices.gov.au/customer/services/centrelin...](https://www.humanservices.gov.au/customer/services/centrelink/age-
pension)

------
api_or_ipa
Not all fuel consumption is the same. Gasoline is way under-priced in the US
when traffic, pollution and road construction costs are factored in. On the
other hand, high quality, sustainably farmed produce is overpriced, most
significantly from sustained subsidies for corn and the associated increase in
the cost of arable land.

~~~
barrkel
There is also the cost of getting the food to you. Often the most efficiently
produced food will be produced some distance from you and a surprisingly large
fraction of the cost will be shipping.

~~~
incongruity
It would definitely be interesting to see the carbon footprint per mile of all
of these options...

------
cafard
Is this an autonomous car, deadheading? If not, you should consider the
resting calorie consumption of the passenger. On a highway, that is indeed
negligible; but a crosstown trip in Washington, DC, used to take me about six
minutes per mile.

The article on travel efficiency shows that a walking person requires about
210 calories per hour at 4 km, about 2.5 miles/hour, call it 85 calories/mile.
For an American consuming 2500 calories/day, a given hour requires about 104
calories: divide that by 2.5, reckon 41 calories in the time it takes to walk
a mile. Now the cost of walking over resting is about 42 calories, and we have
walking down about where he has biking.

Please correct me, for it's likely that I have missed something here.

~~~
dTal
Good catch! Not to mention that the calorie consumption of someone driving a
car is likely significantly more than someone idly daydreaming, both from the
physical activity of steering, braking, shifting etc and possibly also from
the focus required.

------
aji
people who drive probably aren't going to eat less because they're walking
less. also, walking (to me) isn't just about saving money, it's about good
habits and contributing less to traffic and pollution

edit: people travel farther distances in cars than on foot, usually. nobody
would replace a 20 mile commute by car with 20 miles of walking.

~~~
dpark
I don't think the intent is to convince you to drive. It's just an interesting
way to slice the data.

~~~
chillwaves
Not so interesting because they compare food (with highly variable cost and
reason for consumption) to fuel. Going by the cheapest calories available, the
way you would to fill your car with the most economical gasoline, walking is
cheaper. (source is the article)

------
frankus
The math on walking, at least, seems little off: 210 calories per hour divided
by 2.5 miles per hour is 84 calories per mile, which is about 23.5¢ per mile.

Also the cost of driving should really use the average fleet fuel economy of a
country together with the fuel price in that country. That works out to a hair
under 10¢ per mile for 2014 fuel economy and today's gas prices.

The takeaways remain the same, though: Human-powered transportation isn't
especially efficient (unless you're burning calories you would have eaten
anyway), and driving is subsidized up the wazoo in the US.

~~~
dietrichepp
I think the math should also include cost of auto infrastructure, vehicle
deprecation, and the reduced health care costs if you walk.

------
rch
> it’s anywhere from 33-400% more expensive to drive

The article's conclusion including ownership cost fits my intuition pretty
well.

------
kqr2
It's also interesting to consider this calculation from a carbon emission
perspective. From _Climate impacts of biking vs. driving_ :

[http://www.keith.seas.harvard.edu/blog/climate-impacts-of-
bi...](http://www.keith.seas.harvard.edu/blog/climate-impacts-of-biking-vs-
driving)

If you eat a lot of meat and bike, you could potentially have a bigger carbon
footprint than a very fuel efficient vehicle.

~~~
dllthomas
... assuming the biking does not displace other exercise.

~~~
galdosdi
This is a really important point. For many people, bike commuting is partly a
way to avoid having to schedule an extra hour a day dedicated solely for
exercise, so the calories are indeed "free"

------
morgante
Of course, this assumes that you're perfectly fit already and that every
calorie burned translates into additional consumption.

For the vast majority of Americans, that assumption is incorrect. From
personal experience, it's actually the opposite: I eat _less_ on the days
where I go for a long walk.

------
philfrasty
Interesting thought. So going to the gym is literally burning your money. Will
quit in the morning. Thanks

~~~
iconjack
Why put it off until tomorrow? Quit now.

~~~
philfrasty
You are absolutely right. No excuses!

------
frankus
Another data point: a light electric vehicle (ebike, boosted board, etc.) is
about 1-2¢ per mile (~100-200 Watt-hours per mile at 10¢ per kilowatt-hour).

~~~
frankus
Oops, I was off a little ([https://www.electricbike.com/watt-
hours/](https://www.electricbike.com/watt-hours/)), but what's an order of
magnitude between friends?

That should be ~20 Wh per mile, so 0.2¢ per mile with some of the pricier
electricity in the US.

------
astazangasta
How about the cost of manufacturing a car, which has a cost in fuel? Also,
most of the cost of food is labor for its preparation. You're paying for a lot
more than just calories. Food is not made to be energy dense like gasoline,
it's made to be tasty and nutritious.

~~~
martin_henk
Exactly... If you would include the manufacturing/r&d/transport, walking
probably would be the most efficient way if looking at just one mile

------
fpgaminer
The article touches on this, but doesn't directly address it: whether they're
using gross calories or net calories. Gross is the total calories you burn
during that mile. Net is how many additional calories you are burning as a
result of walking versus being sedentary.

Glancing at the wikipedia article which the author uses doesn't clarify this,
nor does Wikipedia's citation. I didn't check the citation's citation.

Clearly we want net calories. Average humans burn ~100 kcal per hour doing
their normal activities during the day, so that could potential change the
figure from 210 kcal per hour walking, to 110.

~~~
mobiuscog
This can't be mentioned enough, because otherwise the travelling by car would
have to include the 'human' fuel element as well.

------
Gustomaximus
This analysis should take the additional calories it takes to walk vs sit to
represent a fair cost of walking. Or add the cost of calories for sitting
should be included in the driving option as these are part of the process.

~~~
gonvaled
Sure, but since driving is faster, and sitting consumes less calories than
moving, the additional calories will be little.

------
spotman
This is a good thought exercise, but kind of comes across like a random
equation looking for an explanation rather than interesting observation in
search of an explanation.

I can't imagine the person driving doesn't spend as much or more than the
person walking on food.

If we are saying that this small amount of money VS drinking oil is where the
line is crossed, then are we not all comfortably well past this zone anyways?

So another way of saying this is listening to music is most efficient if you
listen to a pre recorded song or you whisper only.

------
revelation
This is a good point, petrol is clearly way too cheap.

(We have of course long improved on bicycles. An ultra aero lowracer recumbent
can get 30mph on 120W, covering the 100k for a mere 1kWh at average 25%
efficiency)

------
analog31
Interesting. I think the article would benefit from a graph of the raw data,
i.e., calories per mile, in addition to dollars per mile. I actually wouldn't
mind paying more for food, in return for the pleasure of walking or biking. At
the same time, walking and biking are not an option for a lot of trips,
depending on distance and cargo. Since my daily bike commute is 8 miles round
trip, it's a pretty inexpensive pleasure.

------
schoen
I've seen a number of people wearing versions of this shirt:

[https://www.missionbicycle.com/store/home/gift/53-miles-
burr...](https://www.missionbicycle.com/store/home/gift/53-miles-burrito)

Although if Wikipedia's energy figure is right, that's a 2279 kcal burrito
(which you could _probably_ find somewhere in San Francisco, but...).

~~~
dietrichepp
Oh, burritos can easily get into the 2000+ kcal range. Burritos from Chipotle
get well into the 1000–2000 kcal range without even trying.

~~~
schoen
I tried the calculator at

[https://chipotle.com/nutrition-calculator](https://chipotle.com/nutrition-
calculator)

and added the highest-calorie individual meat (steak), rice (white rice),
beans (black beans), salsa (chili-corn), sour cream, cheese, and guacamole,
and still got only 1365 kcal.

While adding _every single topping_ does reach 2425 kcal, one would have to
order 4 kinds of meat, tofu, 2 kinds of rice, 2 kinds of beans, fajitas, 4
kinds of salsa, sour cream, cheese, guacamole, and lettuce. I would think that
should count as "trying"! :-)

~~~
dietrichepp
Here's some better data:

[http://www.nytimes.com/interactive/2015/02/17/upshot/what-
do...](http://www.nytimes.com/interactive/2015/02/17/upshot/what-do-people-
actually-order-at-chipotle.html)

You can see that 2000 kcal is in the 98th percentile, but the 1000+ kcal range
is very common.

------
dsfyu404ed
Why has nobody mentioned opportunity cost?

There's a huge opportunity cost of not being able to travel as fast and far as
a car lets you. You can't* get an Uber or bum a ride from a friend to your
mother's house in the middle of nowhere on Christmas morning. There's few
parts of the country where walking/biking year round is feasible.

*at a reasonable price point.

------
whoByFire
I'm really surprised at the comparison of motorbikes to cars. I don't own a
motorbike, but my impression was that compared to cars the fuel costs are
trivial. This data suggests a cost reduction of only ~25%. Was it dumb of me
to expect a cost reduction of >75%?

~~~
honkhonkpants
Cars are a lot more efficient than they were a few years ago, and motorcycles
have gone the other way. You can still get a motorcycle that gets 60 MPG or
better, but the mainstream has decided to use their thermodynamic budgets to
build engines with very high specific power and hold the line around 40 MPG or
even less.

Nobody should buy a motorcycle imagining that they have lower operating costs.
Aside from fuel, motorcycles have high budgets for tires, engine maintenance
(due to the aforementioned appetite for high specific power, and relative lack
of scale in their manufacturing), insurance, likelihood of theft or other
total casualty, need to continuously refresh your riding apparel on
approximately 5 year basis, expensive consumable items like drive chains and
sprockets, and so on and so forth. Also there is generally a lack of miles
over which to amortize the time-denominated costs like insurance.

------
madengr
Which is more efficient; a diesel running vegetable oil, or a human?

