Your Guide to Sustainable Travel

As you may already know, Lisa and I are currently living and working in Portugal. Last week we arrived here by bus. I love to get it in contact with the local population in other countries, to get to know other cultures and to taste the local cuisine. Traveling is always rewarding.

We try to make our Western lifestyle as sustainable as possible. The question of sustainable travel comes up again and again. How can we design our travels to make them as sustainable and environmentally conscious as possible? Should we fly, go by train, bus, or just not go away at all?

Without spending several hours researching the various travels, it’s difficult to know what would be the most sustainable travel option for a planned trip. I know that some of you have the same questions running through your heads. Therefore I went through various studies and measurement methods to compare different travel options and to find out how sustainable travel works.

In this article you’ll find a ranking of the most sustainable travel modes and learn why flying is sometimes more ecological as traveling by train and in what way an electric bike has a similar ecological impact as walking.

Here the results of my research to how to travel more sustainably.

What is Sustainable Travel?

To know how we can compare the different travel modes that exist, we need to define the concept of sustainable travel.

The term sustainable travel is often used as a term for the journey as a. It is especially used for the destination and residence selection this includes promoting the cultural and economic development of the visited region without consciously or unconsciously destroying the local nature and wildlife. In this article, we focus on the travel mode itself. We observe the following points.

Infrastructure Costs - Road

Life Cycle Assessment: Life cycle assessment analyses all environmental impacts, in a product’s life cycle as comprehensively as possible. These include the manufacturing of the vehicles, maintenance, operation, fuel production and the impact of the infrastructure needed for the travel mode. In the example of trains, this includes the stations and tracks or roads for walking, cycling or driving by car.

  • Fuel production
  • Infrastructure
  • Maintenance
  • Manufacturing
  • Operation

For similar comparisons often only the more widely known CO2 footprint is used, which greatly affects the results of such comparison, as the high infrastructure and production costs are not included in that metric.

Energy consumption: For the above steps, we use the specific energy consumption of vehicles for comparison.

Greenhouse Gas Emissions: In addition, we want to know what travel modes cause how many greenhouse gas emissions. This is a summary of the gasses, which are blamed for climate change along with the toxic gasses harmful to humans.

These metrics are compared based on per passenger-mile-traveled. This spreads the environmental impact of an aircraft of a low-cost airline, on much more people than that of a car in which only one person sits, for example.

Ranking of the Most Sustainable Travel Modes

7. Car

Traveling by car is on the last place. This applies to various car models with cars having an average passenger number of 1.38. The life cycle assessment of cars can be improved when the ride is shared with friends or through platforms such as BlaBlaCar. Another option is hitchhiking.

6. Plane

Flying performs comparatively better than I would have thought prior to my research. The rather low infrastructure and maintenance costs of flying bring it very close to traveling by train. In comparison to certain more energy intensive trains flying can even have a better eco-balance as the train.

Contrary to many other areas as a rule of thumb when flying not the more expensive option is more ecological but the cheaper option. Low-cost airlines fill their flights and put obstacles for additional bags (less total weight to take off). By the increased number of passengers, the environmental impact per passenger-mile-travelled is highly reduced. An economy class flight is also more ecological as a business class flight, for example, because one passenger uses up less space on the plane.


5. Train

Traveling by train for itself is very energy efficiency, the high infrastructure costs set it back on our ranking, though. This could, however, change in the near future when less energy-intensive materials are used for the train travel infrastructure.

4. Full Hybrid Car

A hybrid or electric car filled with passengers has a better eco-balance as plane or train travel. A road trip with the family or friends is more sustainable in this context. This may also be the case for other energy-efficient cars.


3. Bus

Full buses have a very low life-cycle assessment by their high number of passengers and thus very low environmental impact per passenger. Since the passenger load for tour buses/coaches is often fairly high, I put traveling by bus in the third place. Lisa and I have made our trip from Switzerland to Portugal with a bus. We travel with Eurolines buses.

However, the life cycle assessment for public buses that regularly drive looks different. They often have very few to no passengers in off-peak times and still continue their routes. In comparison, public buses rank lower than trains and planes.

2. Bike / Electric Bike

Regular bikes and electric bikes are far ahead on the list and have almost the same life cycle assessment. The exciting thing here is that the two vehicles even have almost the same life cycle assessment as walking regarding greenhouse gasses. This is because the energy used and the elimination of greenhouse gasses by humans while running is higher per mile than when cycling. This even negates the environmental impact of bikes manufacturing. Therefore the difference is almost negligible.

1. Walking

Not surprisingly, walking has the lowest life cycle assessment. Why not go on a longer journey on foot? I have never experienced this myself, but in regards to this ranking, I would love to try it out once.

The list of the most sustainable travel types is mainly based on the MIT research by Shreya Dave and the Institute of transportation studies research by Mikhail V. Chester. Here, the detailed results of Shreya Dave for those of you who want to know more about the details :-).

energy usage kj pmt
greenhouse gas emissions in kg gge pmt

/ PMT = per passenger-mile-traveled

BART, MUNI, and Green Line refer to three train systems used in the United States.

Depending on which study one chooses, the results of such a ranking could look different. For the reasons referred to in “What is Sustainable Travel?” I chose these studies as references using the life cycle assessment measuring method.

How Many Trips are Still Sustainable?

This is a question which’s answer would be good to know, but unfortunately, I still can’t answer it here. To know how many and how far trips are still sustainable would require a lot of answers. We need to know how much more greenhouse gasses would our planet can support, how many more toxins our cities and bodies could endure and how many more inexhaustible energy sources with consequential damage to the environment we could extract from the Earth.

There are different people and organizations that came to different results. We might not know the exact answers to these questions but we know that we can’t go on as we have been going on so far and that we must change something if we want the next generations to experience a liveable planet.
Therefore it is up to us, both in our everyday lives and on holidays to make our travels more sustainable.

How will you implement the knowledge gained from this article in your travel behavior?

Let us know in the comments.

This research brought me a lot of clarity and I hope that I have served you on your journey as well.


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