Sustainable transport

Ideas, jargon, people

(a discursive personal glossary)

[Still very much under construction, last updated 29/12/09]


Active travel (aka Active transport

  • Jargon phrase to denote getting about by walking and cycling. See also sloth.

  • There is a good compendium of active travel research on the sustrans site.

Attitudes to car use

  • Oft-cited and relevant paper: Jillian Anable "complacent car addicts or aspiring environmentalists? Identifying travel behaviour segments using attitude theory" Transport policy volume 12 issue 1,

  • This paper categorised attitudes to car use among visitors to a National Trust property. The most striking thing about this paper, from my viewpoint, is simply that people's attitudes to car use vary. Yes, of course, totally obvious - except that it's easy to lose sight of. The 'air' (online comments, newspapers, pub philosophers etc) is filled with endless cartoonish rhetoric about oppressed motorists, greedy councils, lycra loutish pavement cyclists and all the rest of it. But when you actually go and ask people - not self-selected people - many of them say something like "well, actually I only drove here because I found that I sort of had to - I had no practical alternative. And actually, driving does have its disadvantages and I'd prefer to have more real choice about it". This is rather what I'd suspected and it's nice to have a piece of pukka research to cite at people.


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Carbon emissions

  • The following figures are in kg of CO2 per km of travel. (Taken from Hillman & Fawcett (2004) How we can save the planet, page 148. They attribute the data to a variety of respectable sources)

    • 0.07 - rail, underground
    • 0.08 - bus, express coach
    • 0.09 - bus, London
    • 0.11 - rail, Intercity
    • 0.14 - car, diesel
    • 0.16 - rail, other
    • 0.17 - bus, outside London
    • 0.20 - car, petrol

  • The figures for cars are 'driver only' but the fuel consumption does not rise much for the extra weight. So cars start to look better if you carry passengers

  • The public transport figures are 'per person' and take into account average occupancies. That is why underground rail and express coaches look so good - they are often full - whereas rural buses are less well occupied

  • The contribution of transport to total CO2 emissions is significant. According to figures from Defra it accounted for 28% of the total in 2007. (This had risen from 24% in 1990).

Carbon Monoxide (CO)

  • Highly poisonous gas produced by incomplete combustion of hydrocarbons. Despite this, it is not really one of the main negative effects of motorised traffic, for two reasons. First, it doesn't accumulate in the atmosphere because it gets pretty smartly oxidised to Carbon dioxide (which isn't poisonous in quite the same sense, but does, unfortunately, accumulate). Second, cars have been fitted with catalytic converters for quite some time and CO is one of the gases they clean up (CO2 is not).


  • Obviously, a terribly, terribly Good Thing. But also, as the word is often used, a piece of rhetorical nonsense.

  • It becomes nonsense when it is implied that 'choice' is a simple thing, exercised on a level playing field - as if you were choosing between the chocolate gateau and the cheesecake. More important choices are not like that because they occur in a complicated web of physical and social circumstances. In many everyday cases we find ourselves pushed, nudged and jostled (often in ways of which we are unaware) into semi-passive opting rather than informed and active choosing. And we may not like the consequences which follow.

  • This is relevent to sustainable transport because there is a strand of rhetoric which goes 'Well people have chosen the car, you know - they have voted with their left feet! You're just some kind of eco-fascist who wants to make life miserable'. Research shows otherwise. As to the constraints that people feel about transport choice, see attitudes to car use and as to making life miserable, see negative effects of motorised traffic.

  • See also freedom and modal agnosticism


  • Hah! I just put that in my list of negative effects because you expected it to be there. Actually, sustainable transport radicals can be pretty cool about congestion.

  • For one thing, living cities always have plenty of interesting stuff going on and lots of people competing for the action - that's the whole point of living in a city! So if it wasn't motorised congestion it would be bicycle congestion or jostling hordes of people on nothing but their own two feet. So a certain amount of urban congestion is inevitable and why not just learn to love it as a part of the tao of the universe? (or the glory of market forces in action - choose your own favourite metaphysical abstraction).

  • No? You think I'm being silly? Then you have to distinguish between reducing the amount of here-and-now traffic and reducing the absolute amount of traffic. A possible danger of some types of anti-congestion intervention is that they might not truly remove traffic congestion but merely smear it over times and places that were previously quiet.

  • What about the London Congestion Charge? That worked didn't it? The concensus is that it did (though even there a few cycling voices grumbled that enabling the motor traffic to move faster was not helpful), and on the whole I'd write a letter to the paper in favour of anything calling itself a 'congestion charge'. But I'd keep on reminding people that 'congestion' is a red herring. We don't want traffic congestion policies, we want traffic reduction policies.

Cycling demonstration towns (CDTs)

  • A super government wheeze to throw some money at various local authorities to help them make a focused effort to increase levels of cycling. I'd say a genuinely good idea, but the results are a bit mixed so far .

  • Here's the official report on how it went with the first batch .

  • the report is quite measured, but it seems the towns have varied in how committed they have been. The authors are quietly positive in tone, but I'm not sure that this might not be strategic and that they are not actually a bit disappointed. John Whitelegg (on page 3 of this) makes his opinions rather more clear about what happened to the CDT project in his home town of Lancaster, where the council just didn't get it.


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  • One of the negative effects of motorised traffic.

  • DfT's Road Casualties Great Britain: 2007.(The figures for 2007 only came out in mid-2008 so are the most recent available). Very interesting. For example: the largest difference between the casualty rate for the most deprived and least deprived areas was for pedestrians, from a rate of 70 casualties per 100,000 population in the most deprived areas to 21 casualties per 100,000 population in the least deprived areas. Quite possible that this is because 'the most deprived areas' might also have the most heavy flux of motor traffic?

  • [unfinished: lots more to be said here]


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Ek = 1/2 mv2

  • This is reason that if you, in pedestrian mode, get hit by a car at 30mph you'll probably live but if it hits you at 40mph you'll probably die. You'd never guess this from the tone of sheer self-righteousness with which people talk about speed cameras, when they are in driver mode.

    • Ek is the kinetic energy of a moving object - the amount of whumph it delivers
    • m is the mass of that object
    • v is the velocity it's travelling at

  • The important thing to note is that it is velocity-squared. Which means that a small increase in speed will deliver a bigger increase in whumph than you might expect.

Effective speed


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Faff factor

  • I coined this term to refer to the trivial-seeming work which can nonetheless put you off using one of the more sustainable modes. It is closely related to the more academic concept of social speed.

  • The FF could even be roughly quantified as: the ratio of time spent on travel-related activity which is necessary but static, to time spent actually moving to your destination. For example, urban walking has a very low faff factor; you just put your shoes on and go.

  • A high faff factor and the whole thing seems like too much trouble - if you want to promote a particular mode you want to keep the faff factor low. This is one of the reasons utility cycling advocates get upset about the promotion of helmets and hi-viz clothing - it increases the amount of stuff you have to buy, take with you and worry about, increases the general faff. (In support of this, note that there have been decreases in the rates of cycling in places where helmet laws have been introduced).

Filtered permeability

  • Jargon phrase. 'Permeability' refers to the ability of traffic to get to places in a city (nice image, I suppose, of a city taking up people like blotting paper). 'Filtered' is the idea that we should select those who are allowed to so permeate.

  • Here's a nice explanation of FP and why it is a Good Thing, by Steve Melia of UWE


  • Here's a chunk of argument worth quoting. It's from Stephen Joseph, director of the Campaign for Better Transport (aka Transport 2000). Unfortunately I have lost the full reference but it is from something called the blue book on transport and was directed at conservative party policy makers.

    • "... the motoring manifesto is really State planning masquerading as libertarianism. The argument runs: people want to drive cars, it is part of a fundamental freedom to move around, and any impediment or charge on this, beyond perhaps a ring-fenced contribution to pay for road building and maintenance, constrains that freedom. The truth is rather different: motoring, unlike other transport and economic activity, is not charged at the point of use. Once the tank has been filled and (sometimes) vehicle tax and insurance paid, people are free to use the roads as they like, at the times they like. Sometimes so many of them want to use the same stretch of road at the same time that congestion occurs. In all other areas of the economy, the price of scarce goods rises to reflect demand. Because there is no price for using roads, people queue. To deal with this unpriced excess demand, the State then steps in and centrally plans trunk roads using bureaucrat-generated forecasts of future traffic based on past trends. To build these roads, it then compulsorily purchases private property, after a public enquiry in which it is not possible (following a 1980 House of Lords ruling) to challenge the principle of the project and the forecasts underlying it, only the detailed routing and mitigation measures.

    • "Sound familiar? This process has several of the characteristics of Stalinist central planning which in other areas conservatives have taken steps to abolish. Like Stalinist central planning, it also doesn't work. [ ... ]

    • "The politics are also not as good on speeding traffic as they might look. The public is suspicious of speed cameras being used to raise money, but that is about the public's distrust of the State, not an opposition to cameras or to speed restraint. Huge majorities of the public - indeed of members of motoring organisations like the AA - support speed cameras, and not just in accident black spots but on residential streets, in villages and around schools. [ ... ]

    • "Much car use is not a choice, it's enforced by State decisions on road building and land use planning"

  • Gosh! Wonder what John Stuart Mill would say about all this?


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  • A possible negative effect of motorised traffic, this word was used by geographer John Adams in his 1996 paper Can technology save us? It seems he hasn't changed his mind about his rather depressing conclusions since then.

  • He uses the term 'hypermobility' to argue that although mobility is a good thing, beyond a certain point it might start to have gradually increasing negative consequences. He makes the point that although hypermobility doesn't prevent us having lives and making friends, it is not a direct substitution for the more local experiences we would otherwise have. If you travel outside your neighbourhood too much, if most of most people's lives start to be lived away from their immediate locality, it means that there no longer is a "locality" - the world becomes one of strangers and a world of strangers is a more dangerous one. Nor are "virtual communities" fully satisfying substitute for physical ones. You grow to know people online and you want to meet them face to face - so perhaps virtual communities generate even more long-distance travel.

  • Eventually, suggests Adams, we might get to the point where our increasing ability to travel anywhere-anytime results in a world that no-one would actually want to live in. A world where, amongst other things, democracy is impossible. Daft you say? Well read his paper! It's a disturbing argument and worth taking the time over.

  • I find it depressing because I cannot see that there is any limit on our desire for mobility. Obviously, it is better to be able to get about, travel a bit. Obviously, it's bad to be confined to your village or town all your life and never see the sea or visit a foreign country. And yet, if too much casual travel (and who decides what is "casual"?) is as problematic as Adams argues, where do we draw the line? And who draws it? There is no logical point at which increasing travel passes from "life-enhancing" to "life diminishing".

  • Therefore we are stuffed. Well maybe.


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Induced traffic

  • Jargon term that refers to the observation that if you build a new road, to relieve congestion somewhere else, it doesn't work. The new road fills up with extra journeys that were not previously being made. (The image often used is "like digging a ditch in a waterlogged field"). Some people find this pretty obvious, others are astonished and simply cannot believe such a thing is possible. The research shows it does indeed happen and even the Government's very own SACTRA have admitted that building more roads generates more traffic.

  • The increase is brought about by a zillion individual decisions. A new road renders inconvenient journeys more convenient - that's the whole point! So of course more journeys are made - they are more attractive.


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Land take

  • One of the negative effects of motorised traffic that isn't often mentioned. Surely it can't really be that big a deal?

  • Maybe, maybe not - there doesn't seem to be much work on it. Here's a 1994 paper by John Whitelegg. Some interesting points are:

    • the amount of tarmac needed by a vehicle is not just the bare space it takes up when stationary - it also requires at least two parking spaces, space between it and other vehicles and so on
    • faster speeds take up more space - bends and junctions have to be designed with wider radii
    • tarmac doesn't absorb rainwater very well - the run-off could have flooding and pollution consequences
    • tarmac does absorb heat better than vegetation, there might be urban heat island implcations

  • From John Adams: "In the first seven years of this century Britainís motor vehicle population has increased by more than 5 million. They all need somewhere to park. If one assumes that they are allocated a parking space each measured by the distance between parking meters they could all be accommodated in a new car park stretching from London to Edinburgh 60 lanes wide. But this provides only one space for each extra vehicle. Their owners will want parking places at the other ends of their journeys, plus wider roads to get them there."

  • See also parking.


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  • There are three basic measures of 'amount of travel'.

    • By Trip. Might be a bit difficult to define precisely, but the idea is straightforward enough. 'Number of trips' might seem crude, but it does appear to be useful in some circumstances. For example, you might say "There have been x number of trips made on our new tram system since it was built. Hooray!" and I might reply "But the number of car trips in your town has not gone down, so the total number of trips, by all modes, has increased and we can infer that there has been no net modal shift. So boooo!".

    • By Time. There is research to show that we keep the amount of time we spend on everyday travelling pretty consistent. I'll put in a reference when I find it, but I think it's something like a typical commute of 50 minutes has been the average for a long time (I think my source for this is the National Travel survey).

    • By Distance. So, we keep our travelling-time pretty consistent, but there has been both a shift to faster modes and infrastructural changes which mean that the distance we typically travel has been increasing for a long time (and with more distance, more negative effects).

  • Which measure you choose matters particularly with result to safety - there's a nice article with some actual figures here. Gives examples of how this actually works out in practice - though Gareth Rees uses the terms absolute and relative. In absolute cycling fatality terms the UK can look pretty good - and 'safer' than the Netherlands. In relative terms it is three times as dangerous.

Modal agnosticism

  • Jargon phrase for the idea that government shouldn't have a preference for the mode of transport used by individual citizens.

  • The latest (as at December 2009) UK transport minister seems to have reversed this policy, though the idea is still clung to by the Mayor of London, and others.

Modal hierarchy

  • Jargon phrase for the idea that government should have a preference for the mode of transport used by individual citizens. Modes should be favoured in the following order:

    • Walking
    • Cycling
    • Public transport
    • Driving

  • Mayer Hillman argues that cycling should be given a slight policy preference over walking (or at least I think he says this because I'm still trying to locate the paper where I think I read this). If I recall correctly, his line of thought is that because the bike is 3 to 5 times faster than walking and because our typical distances are already distorted by the assumption of car use, only cycling can compete effectively with driving (for the time being). I think this might be right - and more utility cycling will in any case also mean more utility walking.

Modal shift

  • Jargon phrase for a change the mode of transport used.

Motorised traffic, negative effects

Motorised traffic, positive effects

  • Well funnily enough, the main answer to this is also "carbon emissions" because, as things now stand, in many circumstances the most carbon-efficient solution is some form of transport powered by an internal combustion engine. A long distance coach, full of passengers, for example, would be better than a long distance train, modestly occupied. Even cars can be pretty good if they're full of people - certainly better than a rural bus with only two passengers.


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National travel survey

  • An ongoing public research project that interviews randomly selected members of the public (I was actually one of those randomly-selected people in 2006). A serious source of statistical information.


  • The developed country with easily the highest level of cycling ... [to be finished]


  • Traffic noise 'could harm children'. BBC news item. Not sure I've found the paper it refers to, but one of the researchers, Gary Evans, has also produced similar work in: Journal of the Acoustical Society of America (Vol. 109, March 2001). There's a short description here.

  • Evans is an environmental psychologist at Cornell and, although it's tangential to this glossary, has also done work on aircraft noise.


  • Refers to various combinations of oxygen and nitrogen, the two gases which make up most of the air. It takes some serious heating to make them combine - the sort that takes place in an internal combustion engine for example. They have quite nasty effects (respiratory irritant, possible carcingogen, precursor of acid rain, greenhouse gas) so they are one of the negative effects of motorised traffic.

  • Diesel engines are more efficient that petrol, because they use higher temperatures (bit of thermodynamics there), however the same higher temperatures mean they produce more NOx than petrol engines.

  • There's more about NOx chemistry in my Energy glossary


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One false move

  • [to be written]


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  • I try not to get too interested in this issue because with my surname I fear it might be nominative determinism coming to get me ... But it is relevent to land take and, despite the fact that parked cars often dominate the urban environment, is one of those features of the car culture that we all know about but somehow manage not to see in any real sense. American academic Donald Shoup is the sustainable guru here. (See also this comment on the costs of parking).

  • Managing parking can play a key part in travel planning.


  • Small particles of matter in the air, produced by burning of some sort (usually - see below) - and therefore of course one of the negative effects of motorised traffic.

  • Often classified and referred to by size: PM10s and PM2.5s - Particulate Matter 10 or 2.5 microns in diameter

  • PM10's can also be, it seems, produced from tyres - a type of vehicular pollution which has nothing to do with exhaust gases.

PM10, PM2.5

  • See Particulates


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Resource depletion

  • [to be written]

Retail vitality

  • A pretty self-evident term denoting the amount of shopping in a particular location. It is often assumed that reducing personal motor traffic in cities will reduce retail vitality - traders get up in arms about proposals to pedestrianise their high street. However, actual research shows that, on the contrary, keeping the car from the high street might even increase trade.

Risk compensation

  • [to be written]


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Shared space

  • [to be written]


  • I've chosen an entertaining word for something that is, IMHO, one of the worst negative effects of motorised traffic. Doctors are mad keen that we take more exercise. Going to the gym is horrid because it costs money, requires willpower, induces guilt and takes up valuable time. Playing a sport is great for some people, but strangely difficult for many people once they've left school. Whereas if you walk or cycle to work every day it doesn't take up time that you wouldn't have to spend commuting in some other way, it feels oddly painless and it's out-of-doors. Embedded exercise like this is the only thing that's going to work for large numbers of people.

  • So we want an environment that encourages walking-and-cycling - not one that makes driving the default option. You even get more exercise if you take the bus because you have a bit of a walk at either end of your journey.

  • Paper in the Lancet titled: Public health benefits of strategies to reduce greenhouse-gas emissions: urban land transport

  • IEEP paper titled: Unfit for Purpose: How Car Use Fuels Climate Change and Obesity.

Social atomisation

  • ... or, to put it crudely: people living on streets with heavy motor vehicle traffic are experiencing a considerable deterioration of their local social lives.

  • There has been some recent research on this in Bristol by Josh Hart, following on from much earlier stuff by Donald Appleyard in San Francisco.

  • See also hypermobility, a very closely related idea.

Social speed

  • The idea that, when comparing the speeds of different transport modes, the time factor should include all the ancillary but static activity. Say you travel x miles per year, how long does that take you? It takes you the amount of time you spend in the car doing the miles plus the amount of time it takes you to earn the money to pay for the car, its maintenance, fuel, insurance and tax, plus the oddments of time it takes to hunt for parking spaces, fill it with petrol, clean it and so on.

  • Here, (after the model of a famous passage by Ivan Illich, readily findable elsewhere on the net), is a typical calculation of the social speed of the private car, from Lynn Sloman's car sick:

    • "All in all, the typical British car driver in 2005 devoted three and a half of his sixteen waking hours to his car. For this time, he travels a little less than 10,000 miles a year. His average speed is less than eight miles an hour - roughly the same as the speed at which he could travel on a bicycle."

  • Considering 'social speed' alongside my notion of the faff factor there is a small puzzle. The static time associated with cycling is pretty visible - and if that time is too large it puts one off taking the bike. Whereas the static time associated with driving is largely invisible - so much so that we don't realise how much of our lives we have to devote to it. A big part of this is probably to do with sunk costs.

  • Also known as effective speed.


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Traffic, types of

  • Traffic is strictly a term that applies to any sort of flux of people - so it includes motorised traffic (boo! we want less of that) of course, but also hordes of pedestrians and cyclists (hooray! we want more of those). However, pedestrians and cyclists seem to have become what in known in linguistics as the marked form. That is to say, pedestrians en masse are referred to as 'foot traffic' as opposed to proper 'traffic' (the motorised stuff). Good idea to notice when people are doing this - reveals some assumptions.

  • Among motorised traffic there are further important distinctions. Buses of course, but they're usually counted as public transport. The big distinction amongst non-public vehicles is between the cars and the bigger vehicles - vans and lorries. The boos and hoorays become somewhat modified here. There are lots of reasons why it would be better to have fewer cars but it's the bigger vehicles that really put the cherry on it in terms of urban nastiness. The drivers of the bigger vehicles, although often highly skilled, have reduced visibility of small items like walkers and cyclists. They are responsible for a disproportionate number of walker/cyclist deaths, a disproportionate amount of noise and wear-and-tear in road surfaces. Do they make up for all this in terms of making-life-better by way of improved commerce and whatnot?

Travel planning

  • Although this sounds like it means organising your holidays, it is actually a useful bit of sustainable transport jargon. Big organisations generate traffic (employees, visitors) and they can influence how those people travel.

  • Planning permission (such as for an expansion of a factory or hospital) can be made contingent on an organisation reducing the amount of traffic it generates (a "section 106 agreement"). Employers have a battery of possible interventions to guide their employees and customers towards more sustainable travel choices and their particular choice of interventions is known as a 'Travel plan'.

  • Managing parking is an example of one set of such interventions. The pivotal issue is whether an employer allows free parking to be regarded as an automatic perk or finds a way to make visible the fact that it is a valuable priviledge. A surprising fact is that each parking space can cost hundreds of pounds per year to the employer who maintains it. Strategically it is a bad move to start charging for something which has hitherto been free, but the cost of maintaining parking space is such that there are employers who have been able to nudge people into car-sharing or taking the bus or bike by offering a "parking cash-out" - paying people to give up their space.

  • 'Travel planner' is now an official job title with its own trade association - ACT. From what I've read, it's potentially a very interesting job because every workplace is different and the need for manoeuvre and negotiation is considerable.


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Utility cycling, utility walking

  • Jargon terms for cycling or walking which is undertaken for practical purposes of commuting, shopping, visiting friends etc. The terms are used to make a distinction between everyday functional cycling/walking and such sports and leisure activites as mountain biking and hill walking.

  • It's the utility forms of walking and cycling which deliver the heavyweight health and wellbeing benefits. The health benefits are bigger than other forms of excertion because they happen every day (sport is jolly good of course, but it is, I'm afraid, really only for the sporty, whereas getting to work or school or the shops is for almost everyone). The 'well-being' benefits occur because utility walking or cycling, almost by definition, displaces car journeys and so helps to roll back the negative effects of motor traffic.

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