Which transport option is the healthiest?

Transport is the main contributor to air pollution in our cities, and how we move around in them can have huge consequences for how much air pollution we are exposed to. The Healthy Air Campaign teamed up with King’s College London, Camden Council and London cyclist, Vivienne Westwood, to see what travel options are the healthiest.

Our experiment

Six volunteers travelled from the same starting point (Lincoln’s Inn Fields) to the same end point (Castlehaven Community Centre) during a Friday afternoon rush hour in May. Four travelled the same direct route along busy Kingsway, Southampton Row, Eversholt Road and into Camden Town using different modes of transport: walking, cycling, bus and car. The other two walked and cycled an alternative route along quieter streets and a canal footpath. Each volunteer carried a personal air pollution monitor to record their exposure.

We used micro aethalometers* to measure the levels of black carbon (soot) that each volunteer was exposed to, as they travelled on their journey. These are ultrafine particles released by the burning of fossil fuels, such as in vehicle engines and, in particular, diesel vehicles. The micro aethalometers measured the levels of black carbon emitted by the passing traffic.

The results

If asked to think about the problem of air pollution in cities, you might picture pedestrians and cyclists wearing masks to protect themselves from breathing in harmful fumes. So you might be surprised that in our experiment the highest levels of air pollution were recorded by the person in the car, followed by the person travelling by bus. In fact, the car driver was exposed to more than twice the amount of air pollution as the person walking the same busy route, and almost eight times more pollution than the cyclist.

Air pollution video - cumulative air pollution

The reason for this is that the vehicles were travelling in a queue of traffic that produced a stream of air pollution from the vehicles directly in front. This air pollution was brought in through the ventilation systems and trapped within the vehicles, resulting in higher concentration levels.

Meanwhile, the pedestrian was walking to the side of the sources of air pollution and so was exposed to much lower concentration levels and, although taking longer, half the amount of air pollution as the person in the car. The cyclist sharing the same road as the car was most likely able to avoid the higher concentration levels of pollution by not always being directly behind the vehicle in front and because the air was able to circulate freely around them. The cyclist was 13 minutes quicker than the car, and was exposed to an eighth of the pollution.

The lowest pollution levels were experienced by the volunteers on the alternative quiet routes, away from busy road traffic. In particular, the person walking the quiet route was exposed to a third of the pollution as the person walking the busier route. For the cyclists, the difference was most noticeable in the average levels of pollution that were 30% lower for the quieter route.

More benefits to walking and cycling

Our real-world experiment shows that getting more people walking and cycling around our cities not only reduces air pollution but can help reduce how much pollution they are exposed to.

Taking quieter, alternative routes will help drastically reduce your exposure to air pollution, and can also be more pleasant experiences.

However, this is not a sustainable option. People shouldn’t feel the need to wear masks, or have to go out of their way to avoid air pollution. The Healthy Air Campaign is demanding drastic action. Sign up, and help us push the Government to take ambitious action to reduce air pollution.

*Many thanks to Air Monitors Ltd and City of London for loaning us the equipment.


23 Responses to Which transport option is the healthiest? – Video

  1. Mark says:

    Interesting, but could be clearer on the distinction between ambient pollution experienced and amount of pollution inhaled. I presume you are measuring the former, which fails to take into account the fact that cyclists and pedestrians will breathe harder and deeper and hence inhale more of the polluted air.

    I’d really like to see some detailed research taking this into account: for example, on my cycle commute is it worth a long detour to avoid an up-hill bus route section, on the basis I’d be encountering diesel particulates while breathing most heavily?

    • It’s been done, with somewhat different results. Cyclists are exposed to less ambient pollution, but may be inhaling more:

      But if the cycle route follows a less-traffic route (i.e. lower pollution) along a bikeway or greenway, that may lead to lower pollution inhaled.

    • Andrea Lee says:

      Yes the experiment looked at exposure and not respiration rates, which would also affect how much pollution a person breathes in. There are many factors that could influence this such as fitness levels, lung capacity, speed of travel, climatic conditions etc. So the experiment was a simple way of looking at what is a very complex situation.
      However, it’s generally accepted, as mentioned in Beth’s study, that the benefits from cycling do generally outweigh the risks and that a lot can be achieved from reducing your exposure where possible. The latter could be through ensuring that you are not cycling right by the exhaust pipe or by taking a quieter route. Incidentally, these alternative routes can sometimes be quicker because there’s less traffic getting in the way and less traffic lights to stop at.
      It would be hard to extrapolate from any study to give advice to a specific individual. What we really need is for serious action to tackle these emissions in the first place so that you don’t need to have to make the choice of a longer less polluted route or a potentially quicker route with higher pollution levels. Cleaning up the bus fleet and other polluting vehicles and getting more people walking and cycling will result in less pollution for all to breathe.
      If you are based in London then you might be interested in planning your cycle journey with this new website http://cityairapp.com/.

  2. Mark says:

    Thanks, Beth and Andrea, for your helpful replies! The cityairapp is intriguing but it doesn’t seem to have an adequate key or help for me to understand what it is actually telling me! Sorry if I’m being stupid, but I can’t find any explanation of what the slider bar is for or what the different colours mean?!

    • Andrea Lee says:

      Hi Mark. I think they are fair comments to bring up. I’ve passed them on to the people who run the site and they are going to work on them. In the meanwhile the map colouring is based on the combined air pollution index levels as used and explained here http://www.londonair.org.uk/london/asp/nowcast.asp and the slider is just to change the opacity of the mapping layer. Hope that helps!

  3. Hi to all, we, at Y4PT we’d like to launch our second worldwide HealthY
    MobilitY Challenge and we will be happy to replicate something similar?

    We’d like to hear from you all more , guys!!


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  5. Tony Browne says:

    I would like to know if your monitors are noticing metal pollutants like Barium, Aluminium, Barium and Cadmium, this is vitally important to the health of everyone on the planet. Please take the time to check this for our kids sake and please let me know the results.

    • Andrea Lee says:

      The monitors we used measured concentration levels of black carbon. This ultrafine particulate matter is produced from the combustion of fossil fuels (especially diesel), biofuels and biomass. The particles can carry a variety of toxic substances but the monitors was not capable of doing this. There are many toxic substances in the environment as you mention but we don’t have capacity to address them all. However, by focusing on particulate matter (PM) pollutants, in particular from road transport as the main source of pollution in most UK towns and cities, which do carry such toxic substances we are able to address overall the health impacts caused by air pollution overall.

  6. […] Pour en savoir plus, vous pouvez visionner cette vidéo et lire cet article (en anglais): ici […]

  7. Gangadhar says:


    I am curious if the car driver had set the air flow setting to recirculate the interior air? Will the results shown here change if the car was set to recirculate the internal air instead of taking in air from outside?


    • Andrea Lee says:

      Hi Gangadhar. How good the ventilation system is and how it is used is likely to affect the results. In the case of our small experiment we just asked the driver to keep the settings that they already had when they came to take part in the experiment because we were not going to have the capacity to explore all the options. As it is, he had the vents closed but the windows half open.

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  9. […] should I support measures to boost cycling?” sets out the case quite nicely. Studies such as this one by the Healthy Air Campaign show that it is drivers and their passengers that breathe the most […]

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  12. Joshua Taylor says:

    I realise this is an old report. The plots for cycling and bus flatline towards the end of the capture period. Are the sensors saturated?

    • Andrea Lee says:

      Hi Joshua. The graphs show the cumulative exposure levels so the flatline is simply the maximum of this.

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