Impact of various travelling options



Are there any objective resources to estimate the ecological impact of various travel alternatives? Sites like offer to calculate it, but they obviously favour trains. I've asked a question on ferries on Travel SE, but didn't get a complete answer taking everything into account. For electrical trains it obviously depends on the mode the electricity is produced. Are there any canonical resources to decide about the trade-off between ecology and other factors when planning travel?


Posted 2013-01-30T08:59:00.770

Reputation: 1 155

I am sure that the railroad is 1000 times more efficient, just because of air resistance. I have bycicled a little and I know that moving one after another allows you to move 2x faster (tandem bicycle). That is, you do not loose any energy when travel after somebody in front of you, who pushes the air away. Since the train is 100 times longer than the plain, it is as much as efficient. But, you need to mantain the road. If fully loaded train departs every 10 minutes the road cost is almost 0. However, if empty trains travels once per day, the road maintanence is huge. Take the train. – Val – 2014-02-08T00:24:07.407

@Val Just to play the devil's advocate for fun: there's less air resistance at cruising altitude ;). Amtrak claims only a 30% larger carbon footprint than cars or flights, I find that surprising... – gerrit – 2014-02-08T14:06:38.130

The resistance is square of speed - it is crazy for the airliner at 900 km/h. Hardly the slight reduction in air density seriously compensates it. We can eliminate the air resistance completely with the vacuum-tonnel trains. Regarding the Amtrak, how do you account the road utilization (do you see my argument)? There is something wrong since reveals that train is 1000% - 2000% more efficient.

– Val – 2014-02-08T16:29:33.300

@Val Thanks for the air resistance correction. In any case ascending is very energy-intensive. I don't know about the Amtrak calculation, I just know this is what Amtrak claims in their advertising. Likely it gets worse because the occupancy of a typical airplane is (much) higher (per volume) than of the long-distance Amtrak trains. – gerrit – 2014-02-08T23:43:36.773

But ascending allows you to travel the second half of path "free of charge": you simply gain forward energy from descending. The occupancy of the vehicles is what I am telling you about. We must consider the transport lines completly loaded. Such comparison would allow us to move in the right direction. Otherwise, we get the destruction of the city: people buy cars, this unloads the busses and trollies. The empty busses become more expensive and departure more ralely. This further detracts people from the public transport. People build suburbs instead where public transport is total absurd. – Val – 2014-02-09T14:38:11.350

Actually, I mean that Amtrak claims a 30% smaller footprint, not larger. 30% larger efficiency. – gerrit – 2014-11-10T22:20:07.413



Long question, short answer: No.

There is nothing like an universal database on carbon footprints or similar. Of course there are a lot of websites which allow you to calculate the impact of - for example - travelling by plane or by car. But the actual calculation of such values is very complex and always comes along with a lot of research.

You mentioned the example of trains (Deutsche Bahn). Let's dig into it. What do we need to know for an objective estimation of your ecological impact?

  • Model and size of train (ICE, IC, EC, RE, RB, S-Bahn, Tram, ...)
  • Type of energy used (diesel, electricity, ...)
  • Quantity of energy used
  • Average speed, number of stops
  • Number of passengers (occupancy)

With these accurate numbers you could calculate your ecological impact (carbon footprint) for traveling by train. I doubt that the Deutsche Bahn for instance is able to provide you with all these data. And even if they could, it's getting more complex. For example - if a train uses electricity - how do you know how the electricity was produced? It's a huge difference on the ecological impact if the train is powered by coal power plants or by renewable energy sources.

All you get is always some vague estimations. Let's have a look at flights. This is a very hot topic and a lot of sites on the internet offer some sort of calculators. Let's compare some.

One-way-flight Berlin (TXL) to Tel Aviv (TLV) - ca. 3,000km

The numbers above already tell you a lot about the "objective" nature of this issue.

Have a look at this one. This one allows you to adjust more parameters, for example type of plane and overall occupancy of the plane. Maybe a better resource. But still no full objective resource to estimate your travel impacts.

Well, I hope this is enough to answer your question and explained why I said "No" in the beginning. Calculating carbon footprints takes a lot of time for research or else you will only get very rough - sometimes unusable - estimates.


Posted 2013-01-30T08:59:00.770

Reputation: 1 127

2I would suggest changing 'Energy' to 'Fuel' in the Type and Quantity categories of your list, then adding another entry: Energy required to process and deliver the Fuel. Another thing to consider is: How much energy went into the production and upkeep of the vehicle system itself? Such as the train and rails; plane, airports, control towers; automobile and roadways; etc. As you point out, there are far to many variables to be able to accurately calculate the "complete answer taking everything into account". – Prymaldark – 2013-01-30T12:03:18.130

When considering energy, don't forget to consider the electrofacility type - carbon reactors producing most CO2, water energy means destroying immense areas of landscape, usually mountain forests, while nuclear reactors have only moderate impact (water warming) when handled correctly and not in extreme-danger zone such as Fokushima (often earthquakes and tsunamis) – Danubian Sailor – 2013-01-31T05:43:37.870

1EnergyNumbers: LCA database are like a universal database of carbon footprints, but they are not that. The questioner explicitly wants a very specific answer, and there's no reasonable way for such a thing to exist (exactly how many people will be on the train, what mix of electricity sources will be in use at that moment, etc). – Móż – 2013-08-11T22:52:23.810

1You write: "There is nothing like an universe database on carbon footprints or similar" - but there are things just like that. That's exactly what LCA databases are. – EnergyNumbers – 2013-02-01T19:23:41.153

@Prymaldark, Why should we consider the production and maintanence cost of the road but not its utilization? Do you count the cost of building a railroad per trip? Your trip actually changes that balance. You may decided that building the railroad is too costly and prefer the plain whereas actually even 3% loaded railroad can be more energy-efficient than plain. And, if you choose to travel by train you reduce the railroad footprint. Why not to account this? – Val – 2014-02-08T00:31:33.370


While this doesn't fully answer the question in terms of ecological impact, David MacKay provides a good chart of the energy use of various modes of transport, here.

I'll extract some figures from it (they're approximate, from me reading off the vertical axis). They refer to typical occupancy unless otherwise stated.

Note that, as pointed out by a commenter here, the first two figures are far too high - this may be a problem with reading off the very bottom of a linear y-axis scale. The others should be considered as approximate (but useful) estimates, rather than accurate results.

  • Cycling: 2 kWh per passenger km
  • Walking: 4 kWh per passenger km
  • Tram: 10 kWh per passenger km
  • Electric train: 15 kWh per passenger km (2 if full)
  • Bus: 31 kWh per passenger km (6 if full)
  • Turboprop aircraft (full): 39 kWh per passenger km
  • Boeing 747: 52 kWh per passenger km (42 if full)
  • Car (single occupant): 80 kWh per passenger km (20 if full)
  • Range Rover: 112 kWh per passenger km
  • Helicopter or private jet: 150 kWh per passenger km


Posted 2013-01-30T08:59:00.770

Reputation: 2 962

1You have to be very careful with that book: the author is very skillful at arranging the underlying assumptions to give the numbers he wants. These aren't necessarily the numbers that best reflect reality. – EnergyNumbers – 2014-01-16T12:07:14.613

@JackRyan oh, I don't have the time to go through the whole book, and this problem is endemic in it. So this is just a quick caveat: some of this book's significant assumptions are invalid, and so the numbers should be used with extreme caution. – EnergyNumbers – 2014-01-16T15:13:30.610

1@EnergyNumbers hmmm, well I think style of answer adds a significant amount of value and context- any chance you could provide a similar list but one whose assumptions you think are more appropriate? – Jack Ryan – 2014-01-16T16:00:29.353

The first two lines (Cycling: 2 kWh per passenger km, Walking: 4 kWh per passenger km) are totally wrong, and don't even match basic reality checks: the cycling figure is out by a factor of about 30. So how accurate are the other figures? – andy256 – 2014-10-30T00:09:00.943

@andy256 hmm, I take your point about the first two. Note that these numbers are from me reading off the y-axis of the graph in the link; it may be that the points have been moved slightly for legibility, since their correct positions would probably have been right on top of the x-axis. As to the accuracy of the others: Most likely low accuracy, but useful in a ballpark sense. The book that they come from is all about approximate-but-useful estimates. – Flyto – 2014-10-31T13:50:20.557


Yes, there are such databases. These are Lifecycle Cost Assessment (LCA) databases.

They are very difficult and expensive to build, and expensive to maintain. And they exist. You'll need to do a web search for LCA database and your region, but they are out there.

The EU has several, for different purposes. Here's the LCA database from the EU Joint Research Centre. And this is a US one from NREL.

Note that it's rather difficult for air travel, because of the high uncertainties around the multipliers that should be applied to aviation emissions.

And for public transport generally, there's the rather vexing question of whether you should use short-run marginal cost, or long-run average cost. If it's a journey you are going to make frequently, then it's definitely average cost. If it's a one-off trip, and the provider has historically shown very few changes in supply in response to changes in demand, then maybe, just maybe, short-run marginal cost is relevant (but there are plenty of experts who'd disagree with me on that point, so take it with a large pinch of salt).


Posted 2013-01-30T08:59:00.770

Reputation: 11 313