[hollerith]

The higher the density, the more vehicles get in each others way.

If your reply is that the vehicles are not needed because everyone can just walk: it takes more energy and more carbon emissions to walk a mile than it takes to drive a vehicle a mile -- and that's before we get to transporting things other than people. (Growing food is very energy intensive; walking burns food.)

[circlefavshape]

A 155lb human burns 177kcal when walking at 2.5mph[1], so that's 71kcal per mile

There are 340kcal in 100g of wholemeal wheat flour[2], so walking one mile takes around 21g of wheat

Wheat flour creates carbon emissions of 0.80 kg CO₂e/kg [3], so walking one mile creates carbon emissions of 170 g CO₂e

Driving a vehicle powered by gasoline produces tailpipe emissions of around 400g per mile [4]

[1] https://www.healthline.com/health/calories-burned-walking#Wa... [2] https://knowledge4policy.ec.europa.eu/health-promotion-knowl... [3] https://apps.carboncloud.com/climatehub/product-reports/id/9... [4] https://www.epa.gov/greenvehicles/greenhouse-gas-emissions-t...

[circlefavshape]

However if the calories from your walk come from beef ...

100g of beef gives you 217 kcal [1], so you need 33g of beef for your walk

Carbon cost for beef is 99.48 kg CO₂e/kg [2]

So walking one mile fueled by beef creates ~3.3kg of carbon emissions, over 8 times what would be emitted if you drove

[1] https://www.healthline.com/nutrition/foods/beef#nutrition [2] https://www.statista.com/statistics/1201677/greenhouse-gas-e...

[circlefavshape]

Oh and it turns out the carbon footprint for beef varies significantly by where the beef is raised. Average carbon footprint per 1kg of beef in the EU is 22.1 kg CO₂e [1], so if you're in the EU your beef-fueled 1 mile walk emits ~730g of CO₂e, a little under twice what you'd have emitted if you drove

[1] https://www.thebeefsite.com/news/33676/uk-beef-carbon-footpr...

[burntwater]

If I'm reading this right it's not quite apples for apples, as it's comparing the cost to create and move the beef, but doesn't consider the cost to create the car, only the movement of the car.

[scott_w]

Except the only people who eat that much beef are certainly not walking anywhere so it’s a fun “statistic” that has no basis in reality.

[mactrey]

A car driver could easily eat the same amount of food as a walker, the extra calories would be stored as fat. This also ignores upfront CO2 output from assembling and delivering the car and increased CO2 output from maintaining car infrastructure vs. pedestrian infrastructure. Not to mention numerous other externalities.

[leereeves]

Don't forget that the person would be burning calories even if they weren't walking.

[circlefavshape]

The figure for calories consumed when walking is excess calories consumed (compared to sitting still)

[leereeves]

Are you sure? It doesn't say that.

[circlefavshape]

I am sure. Think about it for a minute and you'll see why

[leereeves]

I don't. Could you explain what you mean?

Here's what I found: the formula given in the article is "calories burned = BMR x METs/24 x hour"

But the METs for lying quietly is 1. The author certainly forgot to subtract 1 from METs in that equation, and could easily have also forgotten to do so when calculating the given numbers.

https://pacompendium.com/inactivity/

[simonw]

"it takes more energy and more carbon emissions to walk a mile than it takes to drive a vehicle a mile"

I've never heard that before, can you expand on that?

[everforward]

I wouldnt be completely surprised if it were true, though I lack the background and willpower to try to get an actual answer lol.

My thought process is that food also implies some level of driving (delivering pesticides/fertilizer, driving crops away), the fertilizers are fossil-fuel derived, and if you count the sun it takes to grow crops to eat (or worse, as feed for meat).

The whole chain is pretty inefficient, too. Crops are pretty good at converting sunlight to stored energy, but animals and us are bad at retrieving that stored energy. The losses compound if we're eating meat.

Walking isn't a particularly efficient method of movement either, to my understanding.

The energy gets a bit spurious though. One could argue that if we're going to count sunlight going into the crops, we should do the same for the sunlight that raised the dinos so they could become oil.

I also would wager that starts and stops would impact this heavily. The human weighs a lot less so they can accelerate/decelerate much cheaper. The car would have a better edge on a long, straight mile with no stops.

[OkayPhysicist]

A human walking is absurdly efficient, as anyone who's ever tried to outrun a bad diet can tell you. Running or walking a mile burns ~100 extra calories relative to sitting on your couch. Unless you're putting active effort into not doing so, most diets fluctuate by far more than that.

[hollerith]

Sure, but it is also true that food that is healthy for people is an absurdly expensive form of energy compared to gasoline.

[wolverine876]

If we make free the largest costs of gas, greenhouse gas emissions.

[hollerith]

Even if we count the cost of the co2 emissions: it probably takes more petroleum products to grow the food for the walking delivery workers than it takes to fuel the delivery truck.

[hollerith]

I don't remember where I heard it, only that it was an expert on agriculture saying it.

The easiest way to see that it is plausible is to note that only 400 years ago, something like 90% of all human labor went into growing food, which is the way agricultural societies had always been everywhere. The way society was able reduce that to the 5% or so it is today was to use fossil fuels. The first big reduction came with the mechanization of textile production, freeing the food-growers from the need to make their own yarn and weave it into fabric to make clothes with. The tractor was of course also responsible for a drastic reduction in human labor as input to food-growing. Also, the replacement of horses with trucks for transportation of food from the farm to the nearest rail head or port or river (and transportation of inputs like fertilizer to the farm) meant that the food-growers could concentrate on growing food for people now that horses were much less needed.

It's not just the extra calories needed to walk as opposed to rest or to watch television: it's the fact that a single person in a delivery truck can do the work of a dozen people who have to do the deliveries on foot, and keeping one person alive and productive costs only one twelfth as much as keeping a dozen alive and productive -- even if no one walks anywhere or does any exercise. Sometimes for example in order to remain alive and productive, one of the dozen will need to visit a doctor. The doctor requires food to stay alive and productive. Doctors don't live forever and so need to be replaced, and that is an expensive process in part because medical students need food and lots of other energy-requiring things to stay alive and able to learn (and to grow from babies to people mature enough to go to medical school).

My guess is that that analysis continues to hold even if the dozen delivery workers can take public transportation as well as walk although maybe we have to replace "dozen" with "six".

I'm not saying that restricting vehicles in Paris is a bad move: I'm just saying that the effects on, e.g., carbon emission is not obviously good and that the planners who chose (e.g., https://en.wikipedia.org/wiki/Haussmann%27s_renovation_of_Pa...) to devote a large fraction of the area of cities to make it easy for vehicle traffic to flow were not just stupid benighted fools or evil people bent on making life worse for everyone.

[abdullahkhalids]

When people suggest that we reduce the number of cars driven, they are generally not talking about reducing commercial delivery vehicles [1]. Obviously our civilization depends on moving essential stuff around, and we need to do continue doing that, albeit with a electrified fleet of trucks/vans. The problem is with private cars, electric or internal combustion.

[1] Excluding Uber style car-based food delivery services.

[hollerith]

OK, but some people here are asserting that the more urban density, the better, and neglecting to consider that if the density gets high enough, the commercial delivery vehicles are stuck in traffic most of the time or the residents of the city refrain from buying things that would enhance their lives if it weren't so expensive or tedious to move things around the city.

[hirsin]

Which is why if you've ever lived far outside the city, you're tired of people from the city coming out to visit you to buy all the stuff they can't get in the city.

Oh, no, it's the other way round, mostly. It's easier to deliver a quantity and variety of goods to a dense area than the sticks. Which is why "go shopping" is a suggestion for people going to NYC, not Tucson.

[hollerith]

In deciding between a city where personal vehicles are banned or discouraged and a city where they are allowed, noting the virtues of cities over rural areas is relevant how?

[mitthrowaway2]

High density is what enables mass rail transportation, which is much more efficient than personal vehicles.

[bombcar]

Mass rail is most efficient when it's full.

https://afdc.energy.gov/conserve/public_transportation.html - a full car gets amazingly close to a average train (USA).

And this is seen in that trains are most common where they can be mostly full.

What's scary about that is how quickly busses just get outclassed - they have to be as big as their biggest loads, but they're usually empty.

[mitthrowaway2]

How often do you see a full car? Average vehicle occupancy is 1.67, and has been for years.

[bombcar]

Quite often! But usually in the mirror/kid cam, because I'm driving the family somewhere.

[bezier-curve]

> it takes more energy and more carbon emissions to walk a mile than it takes to drive a vehicle a mile

Do you have a source for this? Sounds questionable.

[fnord123]

It's false. People will not go into suspend mode when not walking; they still burn calories. A very large person would burn about 130 calories walking a mile. i.e. one large latte. And most people who are this large are not at risk of a caloric deficit by burning an extra 130 calories.

[mrguyorama]

Humans are INSANELY efficient at walking. That's why walking and running are terrible ways to lose weight.

[itishappy]

About 2x as efficient as a Model 3.

https://en.wikipedia.org/wiki/Energy_efficiency_in_transport

[mrguyorama]

Yeah well I'm not exactly 4000 pounds or going 60mph hah

[ramblenode]

I agree that OP's assertion sounds dubious (especially considering the entire supply chain) but calories are a measure of energy, not CO2. You need to know the rate of CO2 emitted per kcal.

[hollerith]

I'm not claiming that the CO2 exhaled by people is relevant. I'm claiming that growing food requires significant energy inputs unless you want to go back to the world where most human labor went into growing food.

[SV_BubbleTime]

A single mile, no.

100 miles? That seems very likely. That happens far quicker for the energy leaking heat machine sitting in the seat.

So, while maybe the theme of the statement is correct?

[scott_w]

It's simply not.

[resonantjacket5]

The problem that this is the wrong measure to use emissions per mile, when it's really about emissions per trip.

A car flying down the freeway uses less emissions per mile, but if one is traveling 50 miles versus just walking to down the block the former is using a lot more emissions even if it is more efficient per mile.

[scott_w]

This is simply abject nonsense. I know the research you obliquely referenced and it assumes you specifically fuel that movement by eating beef burgers. And even that's on shaky ground.

You can use your eyes to instantly observe that car drivers are not reducing their caloric intake to compensate for the fact that they "save" that energy by not walking.