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Long solo car trips as bad as air travel for climate: study

Air travel has the biggest impact on the climate per trip, but travelling long distances alone by car could be just as bad…

Travelling long distances alone by car could be just as bad for the environment as air travel, the study showed. Flickr/kap4001

Air travel has the biggest impact on the climate per trip, but travelling long distances alone by car could be just as bad for one’s carbon footprint, a new study has found.

The study was conducted by researchers at the International Institute for Applied Systems Analysis (IIASA) and the Centre for International Climate and Environmental Research - Oslo (CICERO) and published in the journal Environmental Science and Technology.

The researchers compared the climate impacts of different forms of transport for a travel distance of between 500km and 1000km, typical of business or holidays trips.

The researchers calculated the carbon impacts of various forms of transport by considering vehicle occupancy, fuel efficiency and climate impact over time.

Jens Borken-Kleefeld, Research Scholar on Mitigation of Air Pollution and Greenhouse Gases at IIASA and co-author of the study, said the formula was globally applicable.

“We took the example of Europe because we come from here and we understand the transport systems here, but the chemical and physical mechanism works the same,” he said.

“If you want to adapt the study to Australia, I think you have to choose the right aircraft – this isn’t a big deal because there’s only two air companies globally, so it’s either Boeing or Airbus that you’re flying. The trickier variable is the amount of pollution that’s coming out from the engines.”

Air vs car

Aviation was shown to have the biggest climate impact per person per distance travelled.

Its climate impact was shown to double when “short-term climate forcers” such as condensation trails that form behind travelling aircraft, thin wispy clouds called cirrus clouds and ozone were taken into consideration.

Graph showing a transport mode’s climate impact over time and distance is lessened with both higher occupancy rates and fuel efficiency. ACS Publications

The study showed that even a couple of passengers in a small diesel car could leave a smaller carbon footprint than the average coach or train, which are shown to have the least climate impact on the whole.

“Here we differentiate load factors so that if you look at the diagram you can read that, ‘OK, this is the number of passengers in my car, this is my climate impact’,” Dr Borken-Kleefeld said.

“Now you can compare it and see what would be the equivalent if I travelled on train or if I took the aircraft?”

Dr Borken-Kleefeld said his study’s conclusions could be useful for transport policy-makers.

Local conditions

Cameron Gordon, transport economist from the University of Canberra, thought the results were “generally transferable” to an Australian context, but the method to obtain them was “all too simple to get a more definite measure of emissions based on travel choices in a particular city or region or country.”

Professor Gordon, who was not involved in the study, said it would be difficult “transferring the results from Germany, which has a certain road network, and of course no maximum speeds on their autobahns [highways] – which would be worse for emissions, per mile travelled by car – to the kind of conditions we have here, with lower speeds and longer distances.”

Dr. Borken-Kleefeld agreed, but pointed out that key to the climate impact from car travel is the fuel economy.

“Hence transferring our findings to Australian cars means adjusting for the local fuel economy, and then you can essentially read off the result,” he said.

Jago Dodson, Director of the Urban Research Program at Griffith University, said that the study was easily applicable to the Australian context.

“Our vehicle-emissions profiles would not be completely different to those in Germany, and it would give you some indication of the relative carbon impact of the different modes of travel between say, Sydney and Melbourne or Sydney and Brisbane,” said Associate Professor Dodson, who was not involved in the study.

“Where the study might be of interest in Australia would be around debates about the high-speed rail project, or the potential for constructing high-speed rail links between Sydney and Melbourne,” he said.

“What the study does indicate is there’s a fairly substantial climate impact saving from switching away from aircraft to trains or diesel coaches, so certainly this could be used as a starting point for further consideration for a high-speed rail option.”

Join the conversation

21 Comments sorted by

  1. John Kelmar

    Small Business Consultant

    I would go even further and suggest that we progress further and faster with alternative fuels for cars, such as solar, water, atomic, etc, which are less harmful to the atmosphere.

    Unfortunately those that tried this many years ago found that their work was stymied by the petrol companies who were keen on profits over economy and pollution. Governments have jumped on this bandwagon by imposing taxes on petrol and other fuels, so are less inclined to pursue alternative fuel sources.

    1. Ben Neill

      Mobile/Web Applications Developer

      In reply to John Kelmar

      I think other than governments that have nationalised oil, they mostly don't care, as whatever replaces petrol will be taxed similarly.

  2. Nick Fisher

    Programmer & Analyst, pt student

    I would be interested to know if this comparison includes the total life cycle emissions associated with the infrastructure needed for the different modes (Chester and Horvath from UC Berkeley published a very interesting paper on this in 2009).

    1. James McIntosh

      logged in via LinkedIn

      In reply to Nick Fisher

      One catch with transferring these conclusions to Australia is that greenhouse emissions our electricity is considerably higher than in Germany. Assuming equal energy efficiency and passenger loading, a Victorian train would generate roughly double the GHG emissions per passenger kilometre that a German train would generate. Other mainland states would be somewhere in between.

      Also, the car emissions seem a bit high in the graph. Assuming a fuel consumption of 8 litres per 100 km, which would…

      Read more
    1. Tim Benham

      Student of Statistics

      In reply to Gavin Moodie

      Especially if you sail. In terms of GHG virtue.I think ballooning would have to be up there too, so to speak,

  3. John Holmes

    Agronomist - semi retired consultant

    Thanks for this. As the house rattles from the roar of aircraft taking off from Perth Airport to service the mining industry in the early morning, I have often thought that it is time that a good independent study be published re the total impact of Fly In - Fly out. Sound seems to travels better in the still air just about dawn. The number of takeoffs is not getting less.

    Issues such as the social disruptions in the families of the workers, lack of development in the North West etc which would also benefit the locals there, and the issues of energy hence CO2 emissions etc.

    Also the of the disruptions to the city via sound, traffic etc. A few impinging on the many, is it not?

  4. Chris O'Neill

    Retired Way Before 70

    "Long solo car trips as bad as air travel for climate"

    I remember many years ago calculating the relative economy of air transport vs car transport and came to the conclusion that they were the same with a fully loaded plane compared with a smallish car with driver and one passenger.

    So a driver by himself is definitely worse than a fully loaded plane.

  5. John Doyle


    The quality of the emissions is also a consideration.
    I have heard that the small particulate matter dimensions of diesel emissions is as bad for our health as is cigarette smoke. I believe in Germany there are much stricter controls on diesel emissions than we have here.
    I can't quote any studies though.
    I believe planes dump fuel prior to landing and much of it gets into urban areas.

    1. John Holmes

      Agronomist - semi retired consultant

      In reply to John Doyle

      Been plenty of discussion re diesel particulates of the size about 10 microns or less that can cause problems in lungs, hence the higher emission controls in the EU. Shades of the original emission controls and how long did it take to be implemented.

      I have seen damage on grape vine leaves that was blamed on herbicide drift, but was from oil droplets from both RAAF and commercial aircraft. Both WA and in Vic. This would seem to be escaping oil losses during routine working. Just look at the oil spots in old car parks in the parking bays under the engine bay. However I hope that aircraft are serviced better that the standard middle aged to elderly car. Dumping fuel on landing, not likely unless there is a problem. Too expensive.

    2. Will Hunt


      In reply to John Doyle

      FYI Airbus A380,
      Max. take-off weight- 562 tonnes
      Max fuel load - 254 tonnes
      Max. Landing weight- 391 tonnes
      Bit of a problem here if the pilot needs to go back because he has forgotten his smokes.

  6. Will Hunt


    At a time when we can communicate visually & verbally with virtually anyone on the planet from the office, when we can take take a liesurely road trip and watching the Tour de France, or the footy from the comfort of your lounge room, send detailed plans to someone, enter into a contract, buy stuff online, you name it, there has never been less reason to travel as there is today- and yet, the Airlines and roads have never been busier.
    Am I missing something?

    1. Liam J

      logged in via email

      In reply to Will Hunt

      Yes Will, I think you're forgetting that we travel because we can, not because we need to, it is a function of our appetites & privelidge. Airport departure lounges are perfect place to observe us preen and rank ourselves and others based on level of consumption we can afford, much more visually appealing than a traffic jam. Nobody will mention the 6th great extinction despite it being highly pertinent to the tremendous activity all around.

      Whether by fossil fueled wheel or wing, the human voluntary extinction movement appears unstoppable, and the difference between hyperconsumption & hyperconsumption+ is significant only in niche advertising campaigns.

    2. Will Hunt


      In reply to Liam J

      Yes.. I knew there was something.
      Felt it in my water
      Thank you for that!

    3. James Jenkin

      EFL Teacher Trainer

      In reply to Liam J

      Will and Liam, I think you're underestimating the positive effects of personal interaction across countries and cultures.

      You could equally say we don't need to interact face-to-face with anyone at all - in our street, at work, at the pub - because we could sit at home and skype them.

    4. Liam J

      logged in via email

      In reply to James Jenkin

      Bizarrely false strawman, i'm all for material rather than symbolic interaction.

      And these 'positive effects of [kerosene-enabled] personal interaction' - they fix much carbon? result in reduced pollution? or just make fb friends to sorta justify the next hyperconsuming trip?

  7. Mike Swinbourne

    logged in via Facebook

    Gerard Dean must be on holidays. I expected him to be all over this article.

    1. Gerard Dean

      Managing Director

      In reply to Mike Swinbourne

      Ha Ha,

      I have actually been preparing my Tiger Tank for a model engineering show.

      Thanks for the compliment Mr Swinbourne


  8. Gerard Dean

    Managing Director

    Boy is this line going to be pasted into many future comments on the Mighty Conversation.

    "According to Matteo Gagliardi, Editor, The Converstation, 'Air travel has the biggest impact on the climate per trip'

    It is the perfect complement to that old truism - If you choose to believe in Climate Change and the need to stop burning fossil fuels, then you choose to burn JetA1 fossil fuel to fly to Europe for a holiday, you have chosen to be a rolled gold, card carrying climate change hypocrite'

    A note to fellow commentators, this includes Mr Swinbourne. Why not check out the new UK Conversation site. It is virtually identical to the Aussie one, and as a bonus, our login and passwords allow you to comment on the articles.

    There are few comments, and the ones that are there are serious minded and boring. I suggest they need some Aussie Conversation commentators to spice their lives up.

    Gerard Dean
    Glen Iris

  9. ian cheong

    logged in via email

    Another study as good as it's computer model of climate impact. Airport heat islands have a significant impact on airport-based weather station measurements too.