October 15, 2012

How Will You Travel for Thanksgiving?

Family. Friends. Stuffed bird. Grandma's pumpkin pie. The old homestead. Good wines and spirited conversation. Uncle Joe's special sweet potato bake. There are plenty of reasons why Thanksgiving is the most-travelled holiday in America.

This year, I've started early with seeing what's the best way to get where we're going, in terms of time, money - and carbon footprint.

Focusing on travel over a few hundred miles, I started at carbonfund.org's Carbon Calculator page, which has a helpful link to EPA's report on carbon emissions from travel. The data on high speed trains is from Vidya Kale's Climate Is Our Job blog. Its numbers are consistent with those on Wikipedia's page on energy efficiency in transportation.

There were a few surprises!

For instance, I've been under the impression that it's always greener to travel by train than by car. It turns out that depends on the train and on the car. The train is greener if you compare taking riding the Amtrak train (185 g CO2 /passenger km), to driving by yourself in a large or otherwise gas hogging car: driving solo in a Toyota Sienna minivan, which gets 24 mpg on the highway, your carbon emission is 227 g CO2/km. (To find the carbon footprint for your own car, use UnitJuggler's mpg to g CO2 /km conversion calculator).

However, if you bring six friends in your minivan, the boring trip becomes a social outing, and the footprint per passenger is reduced by a factor 7 (ignoring the slight decrease in fuel efficiency from loading the van): now the per passenger carbon footprint is only 32 g CO2 / passenger km. This is a lot better than that of Amtrak, and better even than that of my VW Golf TDI, which does 45 mpg on the highway, when filled with the four members of my family (39 g CO2 / passenger km)!

As long as you fill all the seats in the car, you can do better than even the average European high-speed train. Swiss trains have the smallest carbon footprint because a large fraction of their electricity comes from renewable and nuclear sources, and because of the high average occupancy of the trains (80%) and the fact that on average each track carries 90 trains per day, so the carbon emissions from building the tracks (even over and through the Swiss Alps) is shared by those 90 trains.

Even regular, not high speed, European trains offer a great alternative to driving: it's safer and more pleasant. And it's much greener than travelling solo in your car.

If Amtrak plays its game right, it could get its trains' emissions much closer to the European average. It's a matter of attracting more riders, which is far from a pipe dream: on the Eastern corridor, Amtrak trains are very popular, and nearly always filled to capacity. Those tracks are well used.

Right now, the US-wide average occupancy of railroad tracks is pretty low, even if you count freight trains. Many trajectories are travelled by Amtrak trains just once or twice a day. And each Amtrak passenger carriage, on average, is only 60% occupied. My own guess is that Amtrak trains use locomotives that run on older technology that those of European and Japanese high-speed trains. All this contributes to the larger per-passenger carbon footprint of Amtrak trains: 4 to 5 times larger than that of a typical European fast train.

Amtrak needs higher speeds to attract more passengers in this large country: In the midwest it does sort of okay (but not great), covering the 1000-mile distance between Denver and Chicago in just over 8 hours; that's an average speed of 125 mph. On the crowded Eastern seaboard speeds slow to an average of 69 mph. Taking the "fast" Acela train shaves a bit off your travel time, but only a bit, and it costs more than twice as much as taking the regular service. To put this in perspective: the record speed for passenger trains is 302mph, attained on a track between Beijing and Shanghai.

Cost & Speed Comparison: Amtrak, TGV, car

New York
Wash. DC
Distance (miles) 229 mi 1000 mi 483
Travel time 3h20m (2h45m) 8h 3h20m
Average speed (mph) 69 (83) mph 125 mph 146 mph
Cost (one way) $ 82 ($ 199) $ 110 $ 146
Amtrak cost per pass. $ 0.36 ($0.87) $ 0.11 /mi $ 0.30 /mi
VW Golf cost ($4/gal) $ 0.09 /mi $ 0.09 /mi $ 0.09 /mi

(numbers in parentheses for Acela trains).


At fuel prices of $4 per gallon and a highway efficiency of 45 mpg, my brave diesel Golf easily beats Amtrak's per-mile cost per passenger. When my family of four takes a trip, we're 5 to 16 times cheaper off taking the car than the train. No wonder the interstates are still jam-pack clogged with cars on Thanksgiving weekend.

Even so, there are signs of a renaissance in intermediate-distance rail travel, and I hope it will in time replace short-haul air travel which is truly wasteful of energy, and not necessarily a time saver. I can't wait to ride that planned high speed train that's to connect San Francisco and Los Angeles in less than three hours. It's time for the country that gave birth to long-distance train travel to catch up with the rest of the world again.

For now, if you're travelling solo and your car does less than 29 mpg, you're better off taking the train, carbon wise. It's certainly more pleasant, with lots of people to meet, power outlets at each seat for your mobile devices and WiFi for connectivity: it beats staring at the tail lights of the car in front of you. If you count delays from traffic congestion, taking the train will be quite a bit faster. Only flying is faster, at least on long-haul trips.

By air and by sea

It came as a real surprise to me that Amtrak's per-passenger carbon footprint is the same as that for a long-haul airplane. If Amtrak installed high-efficiency, high-speed trains it could reduce travel time between Denver and Chicago to about four hours, which is less than the total time you spend travelling by air, if you count the struggle to get through airport security. Moreover, it could reduce its emissions by up to 80%.

Another surprise: in case your turkey is beckoning to you from Paris or from Prague, getting to Europe by flying is greener than taking a transatlantic boat cruise. This is because water presents a formidable resistance to anything trying to get through it, unless you're shaped like a fish. I guess cruise ships like the Queen Mary II, confined to the water surface, don't look remotely like a fish. So flying to Europe is greener and faster than taking a cruise on Cunard. And of course, it is much much less expensive.


But the story is different for freight. For air travel, all that really counts is the weight of the person or the stuff that needs to be lifted into the air at takeoff and kept there until the plane lands. So the per-ton, per-mile carbon footprint of air cargo is about the same as that for human passengers.

For boats, trains and trucks, it's much more efficient to transport stuff, which you can stack to the ceiling, than people, who need room to breathe and move around a bit during the journey. For a truck rolling down the interstate, it's mostly about air resistance, so the carbon emissions of moving cargo by air is much larger than that of truck transport. That, in turn, is limited by the size of the cargo container, so the truck's carbon emissions per ton of cargo moved is much larger than that for a boat or a train that can handle large numbers of containers per trip.

And this is why the 10,000 mile diet, that includes flying in raspberries from Peru in February, is bad for your personal carbon footprint.


The best thing to do for Thanksgiving? Source your food locally. And try not to travel too far. Whichever way you decide to go, you'll be one of an enormous crowd.



  1. Wow! Great Post. It's fun to see all the comparisons in one place. I'll be tweeting it too!

  2. I had never given that much thought. I always solely thought, which is cheaper, flying or driving. Plus for us, it depends on the time frame we will be somewhere, although most of our trips are just under 3 hours away.

    1. For now, driving is the cheapest option by far. Still, the misery of sitting in Thanksgiving traffic for hours (+more carbon emissions!) is enough to push us onto a train.

  3. Great info! We're lucky that we live down the street from my parents. So we get to walk for the holidays!

    1. You are SO lucky! - especially your children are lucky!


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