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A while back, I talked about driving from Bloomington to Chicago (and beyond) compared to a similar train or plane ride. Driving to Raleigh, NC last week gives me the opportunity to see if the results are similar with a different car, number of people, and destination. This time, I also plan to compare costs, which I ignored in my last analysis.

The numbers produced by the carbon calculator and my estimates were off by quite a bit, so I used my calculations and their estimate of CO₂ per person-mile. I believe the difference is that I use exact mileage (as provided by the transportation company) and I’m not using a multiplier for the plane to represent that fact that its CO₂ is released in the upper atmosphere.

The driving distance from Bloomington to Raleigh is about 670 miles. At 49 mpg, that’s almost two tanks of gas (8 gallons each) at $3.40/gallon. That makes the out-of-pocket cost about $50. According to Consumer Reports (subscription required), a Prius has maintenance costs of $2,971 per 75,000 miles. That’s an amortized rate of $26.54 for our trip for a total cost of $76.54. Using the same carbon calculator as before, the trip also produced 274 pounds of CO₂ (19.56 lbs per gallon burned). Since we’re also travelling back, that would double the results but that’s negated by the fact that there are two of us in the car.

Driving the Prius: $76.54, 274 pounds of CO₂, and 26 hours.

There are direct flights from Indianapolis to Raleigh, but Indianapolis is further away from Raleigh than Bloomington is. The total distance is about 990 miles. A round-trip flight for one of us would be 436 pounds of CO₂ (0.44 lbs/person-mile for a medium-length flight) and $245 (assuming we get tickets a month out). The flight itself is 2 hours but it would require another hour to make sure that we’d be able to get through security on time. We’d also have to drive to Indy from Bloomington, which would produce 39.12 pounds of CO₂, cost $6.80, and take 2 hours round-trip.

Flying: $252, 475 pounds of CO₂, and 8 hours

The Amtrak website is pretty hard to navigate (it kept timing out and giving me errors). The biggest problem is that if you’re switching zones (Midwest to South in this case), it won’t suggest routes for you. You have to figure out what the connecting city is on your own. Going from Indianapolis to Raleigh requires a stop in Washington, DC (which actually might have worked out well, since Maggie is making an extra trip up there to visit a friend). The Indy to DC leg would cost $82 and take 18 hours. Going from DC to Raleigh is $43 and 6 hours. Ignoring any layover time, that’s $125 and 24 hours for one person going one-way. The trip is over 720 miles each way, which is 302 pounds of CO₂ (0.42 lbs/person-mile). That makes the round-trip train ride cost $250, produce 604 pounds of CO₂, and take 48 hours. We also have to add in the additional travel time up to Indy (39 lbs of CO₂, $6.80, 2 hours).

Train: $257, 643 pounds of CO₂, and 50 hours

As with the train and plane, we’d have to head up to Indy to take a Greyhound bus. There are 2-3 transfers and it’s about 700 miles. Those 700 miles would produce 462 pounds of CO₂ (0.66 lbs/person-mile). Depending on when we left, it could take anywhere from 16.5 to 22 hours. All of the routes are the same price ($222), so I’ll assume we’d pick the shorter one. Once again, we add in the trip to Indy (39 lbs of CO₂, $6.80, 2 hours).

Bus: $229, 501 pounds of CO₂, and 35 hours

It’s table time!

Once again, the car seems to be the best choice. It costs about a third less than the next cheapest alternative and produces almost half as much CO₂. Even though the car is better in all categories than the train and bus, the plane is much, much faster (over three times as fast!).

It’s pretty obvious why Amtrak makes such a dismal showing. Going all the way to DC before going south adds a whole lot of distance, which increases everything else. While doing some research after my last post, I found out that inter-city buses average less than 7 mpg! With two of us in the Prius, the effective person-mpg is about 100. For a bus to do that well, it’d have to have 15 passengers, assuming that it goes the same distance. Unfortunately, the buses have further to go as well, since Indianapolis is further from Raleigh than Bloomington and they make some detours for stops. I’d guess that a bus would have to have around 20 people in it to match our person-mpg. Based on its CO₂ production, it looks like the expected number for a trip like that is more like 11. I haven’t actually ridden from Raleigh to Indianapolis, so I don’t know if this is accurate for that trip, but it seems plausible based on the size of the bus.

Running the numbers again really makes it hit home why people in the US prefer their cars (and occasionally planes). Trains cost way more and take much longer. Buses are a little better, but aren’t as comfortable and still require you to get to a station somehow. Airplanes cost a lot and produce a lot of CO₂, but at least they get you there faster. In fact, if you look at cost as a proportion of time, the airplane costs almost exactly as much as the car ($78), so you’re basically just extrapolating the cost of the car. That is, if you could pay to increase the speed of the car, you’d have to pay as much for it to get there in 8 hours as you’d pay for a plane ticket.

That doesn’t even begin to account for the convenience. Since we were driving, we were able to carry a bunch of boxes for Maggie’s friend Laura and Maggie was able to take a short side-trip to DC to visit her.

Basically, if you care about cost and have at least one passenger, it makes more sense to drive than anything else. I wish it were otherwise, but until they get some zeppelins up and running, I think we’re stuck with it.

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In my last post, I wrote about carbon emissions for different modes of travel on my trip to WI. Arduous picked up on my last paragraph about how these are potentially unreliable estimates and expanded that into a thought-provoking piece on calculating carbon emissions.

Basically, the problem relates to fixed versus marginal costs. For you non-economists, marginal costs are the cost for one more unit, whether producing another widget at your factory or, in this case, adding one more person to a bus. My article focused on fixed costs, but the real question is which marginal cost is more. Even if a bus produces more CO₂ per person on average than a full car, it’s going to produce basically as much whether I ride in it or not. As Arduous puts it:

… driving a car is only the most carbon efficient method IF the carbon emissions Will and his friends’s weight cause on a plane, bus, or train is GREATER than the TOTAL emissions of the car. Which seems pretty unlikely.

Since none of us weigh much, especially compared to a bus, I think Arduous makes a really good analysis. The problem at an individual level is that your decision depends on factors you can’t know about in advance (basically, how many people will join you on a bus, plane, or train, and whether or not these trips will be cancelled if you don’t go). This seems like a good place to apply rule utilitarianism, even if it doesn’t make sense in the general case.

In basic utilitarianism, you do what creates the most happiness (or in this case, produces the least CO₂). Since it’s so hard to figure that out, rule utiliarian provides some simple rules that help you act in a timely manner. Things like “don’t kill innocent children” or “always ride the bus when possible” increase happiness overall but also makes it so that you don’t have to actually spend the time to run the calculations every time. Which is good, because we can’t, as I mentioned above.

To move from utilitarianism to rule utilitarianism in this case, we need to stop looking at it from an individual point of view and start looking at it communally. The question changes from “how can I travel to reduce my CO₂” into “how can I travel to reduce my community’s CO₂?” It’s a subtle distinction, but it makes the math easier.

To decide that, let’s calculate the break even point between a bus system and a system of cars. Unfortunately, the source for my carbon calculator determines the CO₂ production of planes and trains by dividing their total CO₂ production by the total number of passenger miles which makes the data useless for this. For buses and cars, I was able to grab the Greenhouse Gas Protocol Initiative (GHG Protocol) data that my calculator from the other day uses.

According to their spreadsheets, a 30mpg car produces 186.6g of CO₂ per km (yeah, different units from last post, but it doesn’t matter; it’ll all come out in the wash). A bus, on the other hand, produces 1492.5g of ₂! The difference is so large because buses get terrible mileage (6.7mpg average in the US). This difference between running a bus and running a car is almost exactly a factor of 8. This means that it takes eight cars driving the same distance to equal the emissions of one bus.

If you assume that there are generally about two people in a long-distance car trip, then the bus will have to have 17 people in it before it actually reduces carbon emissions.

This gives us a good break-even rule for travel. If you take a bus and it has much fewer than 16 people in it, don’t ride that route anymore. That’ll discourage the bus company from keeping that route going. If the number is closer to 16, it might be worthwhile to keep riding the bus and encouraging others to join you. If it’s more than 16, you can relax, secure in the knowledge that not only are your carbon emissions low individually, but you’re helping reduce your community’s emissions. Note that this is true no matter how many people you would otherwise cram into your car because whether or not the bus produces less CO₂ depends only on how other people would act, not on how you’re acting.

On a community-wide scale, this helps you make decisions about when to add buses and, perhaps more importantly, what type of buses to get. Small buses, like those sometimes used as school buses, can never be better than cars. It only makes sense environmentally to create a route with a large bus and only if over 16 people will ride each direction.

Increasing bus mileage would help too. Bloomington has started trying out hybrid buses and some nearby parks use propane-powered vehicles. These methods can help reduce the break-even point.

This same analysis should be possible with planes and trains if you can get hold of overall emissions rather than data per passenger-mile. And, naturally, carbon emissions are only one facet of the much larger issue of sustainable living. Even if a bus produces more CO₂ than a car, it might be worth it for other reasons, like traffic reduction.

Personally, I find the carbon calculators valuable for determining which technologies are approximately the same. Driving a packed car versus riding a bus are approximately equal, so I don’t feel bad about the occasional long roadtrip and I also feel good about encouraging additional buses.

On the other hand, rail and plain emissions are so much higher than car emissions that I don’t feel like we’ll be able to meet their break-even points anytime soon. So while it’s true that I, individually, won’t produce more CO₂ if I fly, I’m helping support an industry that might require up to 60 people to break even.

The break-even point is also a sliding scale. As cars get better, it requires more and more people on a given flight, train, or bus to reduce the overall amount of CO₂.

To make a long (and perhaps boring) story short, it makes sense to encourage high-volume busing and discourage low-volume busing even if that puts some more cars on the road. At least from a carbon perspective.

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This past weekend, I drove up to Wisconsin by way of Chicago to participate in PlayExpo 2008. It’s too late now, but in the car I got to wondering what the most environmental way to travel up there would be. There were three of us in the car through Chicago and then four from Chicago to Whitewater, so we’d reduce the carbon emissions per person that way. The best would probably have been to run veggie oil from Maggie’s car, but none of us drive shift. A car with better miles per gallon (like a Prius) would also have been good, but we were stuck with Ian’s car, which gets about 30 mpg highway.

With Ian’s car as a base, I used the Native Energy CO₂ emissions calculator to figure out how much pollution each mode of transportation would produce.

There were three main legs to the trip: Bloomington to Indy (50 miles), Indy to Chicago (186 miles), and Chicago to Whitewater (106 miles). The first and last had to be done by car (either our own or in a rented taxi sort of situation which would be worse in terms of pollution). The drive from Bloomington to Indy produced 32 lbs of CO₂, while the Chicago to Whitewater leg produced 70 lbs, or 102 lbs overall. The car emissions are computed per vehicle though, while plane, train, and bus are computed per passenger. There were three of us going from Bloomington to Chicago and four from Chicago to Whitewater, so the per-person numbers are 10.6 lbs and 17.5 lbs or 28 lbs total.

Those 28 lbs of carbon would be produced no matter how we got from Indy to Chicago, so we’ll ignore them for now. Our drive between Indy and Chicago (186 miles) put 70 lbs of CO₂ in the atmosphere. That’s 23 lbs per person.

The flying distance from Indy to Chicago is about 25 miles less than the driving distance. However, planes create a lot of CO₂ and they create it in the upper atmosphere, which multiplies its impact. A plane ride would have create 212 lbs of CO₂ per person. That’s almost ten times as much as driving!

Okay, conventional wisdom is upheld. Planes are bad. Surely trains are better.

Sure enough, trains are better. Travelling from Indy to Chicago by train produces 108 lbs. per passenger. The travel distance is slightly less with the train than when driving, which helps. If we’d had to take the train as far as we drove, the train would have produced 122 lbs. per passenger.

Even the smaller amount is 5 times as much as driving.

There’s a cool European bus company, Megabus that now services Indy to Chicago. If you order far enough in advance, you can get your tickets for $2.50 (that’s $1 plus their $1.50 service fee)! Unfortunately for us, we didn’t know we were going until the las minute, so the tickets would have cost us $20 each.

But enough of cost. How much CO₂ does the bus produce? Travelling over the same mileage as the car, the bus produces 68 lbs. of CO₂ per person. That’s a lot better than even the train, but it’s still 3 times as much as driving. Hmm… 3 times. That sounds familiar. In fact, that’s how much I divided the driving portion up because there were three of us in the car. It seems like it would have produced about as much CO₂ for a single person to drive as to take the bus.

I have to admit that I’m pretty astonished with these results. I knew flying would be bad, but not that bad. The train was also worse than I’d expected. The big shock was that the bus was almost as bad as driving by yourself! Apparently, the average mpg in the US is about 23, which would adjust things in favor of the bus. If you have a decent car, or a hybrid, you’re better off driving even if you’re by yourself! And if you’re sharing the ride, driving is by far the best option.

Here are the final results, including travel to Indy and Whitewater:

Plane: 240 lbs. of CO₂
Train: 150 lbs. of CO₂
Bus: 96 lbs of CO₂
Car: 51 lbs. of CO₂

Overall, the trip would have produced twice as much CO₂ if we’d taken the bus rather than the car, three times as much if we’d taken the train, and five times as much if we’d flown.

This really underscores the idea that protecting the environment is a many-faceted concept. Even if cars produce less CO₂ for a trip like this, there are other problems connected to them like all that wasted space used for parking lots and garages. Even worse is all the frustration and wasted time caused by gridlock, which would be alleviated by reducing the number of cars on the road.

Of course, I’m aware that these are all estimates. A plane, train, or bus isn’t going to produce that much less CO₂ just because we’re not riding. Still, the concept is useful when trying to decide what sort of long-range travel options we should support!

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Don’t you hate it when someone takes something you’ve said out of context and uses it to support the exact opposite point of view? Chris Goodall, British environmentalist and author of How to Live a Low-Carbon Life has found himself in that situation. Recently, in How Virtuous is Ed Begley, Jr, John Tierney of the NY Times mentioned that Goodall had calculated that it’s worse for the environment to walk 1.5 miles to the store and replace those calories with a glass of milk than it is to just drive there. Most of the commenters assume that Goodall is encouraging people to drive and lambast him under that assumption.

Like many assumptions, it’s totally off-base. Goodall isn’t using the numbers to say that driving is good; he’s trying to show that the current state of food production is terrible. When driving a mile and a half is better than drinking a glass of milk, something has gone terribly wrong. In Goodall’s view, it’s the whole factory farming system.

This analysis, and the similar one about biking at BicycleUniverse.info assumes that you’re buying into that system. If you’re buying local organic milk (or beef, for that matter), then you cut out a lot of carbon emissions (for pesticides, etc.) and reduce others (transportation).

As an aside, the assertion made on the BicycleUniverse.info page that cost implies energy (”Since the costs of water and energy for laundry are much lower than [the cost for driving], they can’t possibly use more energy than driving.”) drives me crazy. There’s almost no relationship between cost and energy density. Maggie and I have this argument all the time when we’re bemoaning the price of fuel. I’ll complain that gas is $3.30 a gallon and then Maggie one-ups me by saying that diesel is up to $4.50. Once you take into account the fact that diesel is more energy dense, though, Maggie spends about half as much as I do to go as far. As a more extreme example, burning wood that you cut yourself is very cheap but very polluting. It’d be much better to use solar to heat your shower water, even though it’s much more expensive.

But back to the original question. When is walking worse than driving? When your food drives out to meet you.

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