Should the war on obesity be a key objective of transport policy?

Posted: September 24, 2011 | Author: | Filed under: Education, justice, health, Public transport | Tags: , , , , , , , , | 24 Comments

I know people who have the option of driving but instead take the train so they can improve their physical fitness. It takes longer than driving, but since they’re going to work anyway, walking to the station is an easy way to exercise. It makes good sense; I’ve walked or cycled to work at various times for the same reason.

However it’s one thing to make a private choice to use public transport in order to exercise – it’s another thing altogether to elevate the war on obesity and other health issues, as a matter of public policy, to the status of a key goal of the transport system. That’s what organisations like the Planning Institute and the National Transport Commission propose, but it’s not self-evident to me that it’s a good idea. It’s worth thinking about it further.

There’s a paradox here. The very point of public transport is to extend personal mobility. At the end of the nineteenth century when everyone other than the very wealthy walked, the arrival of trams and trains greatly enriched people’s lives by overcoming the limitations of walking. Now they could travel further to better jobs or better houses, take the family to the beach on Sunday, or visit friends and relatives in more distant suburbs. The whole point of public transport was to travel faster than walking so people could travel further in the same time.

The panoply of exercise-related issues like obesity are not a transport problem, they’re a social problem. They’re a result of eating more and of expending less effort in all aspects of life, not just in the way we travel. It’s true we are much more likely today to drive than walk, cycle or use public transport, but the avoidance of effort is true of almost everything we do.

Most of us work in jobs that don’t involve anything even remotely like the level of physical effort expended by the average worker of a few generations ago. If we did, Occ Health and Safety would have a fit. On the home front, we’ve had “labour saving” devices like refrigerators, stoves, washing machines and vacuum cleaners for generations. Television and home delivered newspapers mean we don’t even need to go out to get information and entertainment.

Consider the giant strides we’ve made in avoiding exertion over the last twenty years. Computers have eliminated the effort of going to the bank, the booking office, the travel agent or the bookshop. We blow leaves rather than rake them, we use power tools to drive nails and screws, we answer the phone without getting out of our seat, and we cook meals without having to prepare them. We control our air conditioners, central heating, TVs and sound systems with remotes. Climate control means our bodies don’t even consume much energy to keep warm – many children barely know what it means to shiver.

The decline of effort pervades all aspects of our lives, not just how we travel. For better or worse, it’s one of the ways we define progress. So transport – and that essentially means the car – is only one part of the health problem.

And in fact it’s a relatively small part, because the main cause of obesity is what we eat, not how little we exercise. It’s likely to be far more effective to target food than public transport.

Lennert Veerman, Senior Research Fellow at Queensland University’s School of Population Health, points to a recent study which argues the main force driving the obesity pandemic is an increase in consumption. He says the 1970s was:

When the food supply started to change radically. The supply of refined carbohydrates and fat increased and more food was mass prepared rather than cooked at home. The era of easily available, cheap, tasty, highly promoted, energy-dense foods had begun. This view of the causes of the rise in obesity prevalence suggests the likely solutions lie in the area of the supply and promotion of food. And research supports that notion.

He says if governments are serious about tackling obesity their priority should be food. They should tax unhealthy food, limit advertising and restrict availability in schools. He also says healthy food should be subsidised. Read the rest of this entry »

Is inner city living the solution to obesity?

Posted: July 13, 2011 | Author: | Filed under: Education, justice, health | Tags: , , , , , , , | 11 Comments

How much exercise is needed to burn off food?

It’s often pointed out that residents of the inner city, on average, are less obese than residents of the outer suburbs. Since the inner city is denser, more walkable and has much better public transport access than any other part of the metropolitan area, the conclusion seems obvious to many – a key strategy to address obesity should be to encourage higher dwelling densities and better public transport in the suburbs, especially the newer, fringe areas.

The flaw in this thinking is it fails to observe that the inner city – defined roughly as the area within 5 km of the CBD – is a different world. Relative to the suburbs, the inner city has an emphatic over-representation of younger, well educated and affluent residents with fewer dependents. The proportion of the population made up of young singles is three times that of the metropolitan area as a whole and there are twice as many young couples without children.

These are the sorts of people who on average are slimmer because they’re younger, who are of an age where appearance is enormously important, and who are well educated enough to know about nutrition and eschew fast food. They can afford to buy high quality fruit and vegetables and pay for gym memberships. Because they’re more affluent, they have fewer children on average and hence less need for a car.

They live in smaller dwellings so they can be near the CBD and take advantage of its enormous and unparalleled concentration of high-paying professional jobs, its matchless endowment of cultural attractions and its huge and diverse range of social and entertainment opportunities. There’s no other concentration of activity within the metropolitan area that comes even close to the richness of what the inner city offers.

Because they live at higher density, driving is too hard for many trips – roads are congested and parking costs range from expensive to impossible. So residents often walk or use public transport instead. That’s O.K., because they happen to live in that transit-rich, small and unique geographical area where every train line and tram line in the entire metropolitan area – the result of 130 years of construction and at least one spectacular land boom – converges.

So population density and access to public transport are not the underlying forces driving this group’s superior average BMI. Rather, it’s a combination of the small but highly specialised group who can afford to live there, on the one hand, and the special characteristics of the area, particularly the presence of the CBD, on the other.

It’s pie in the sky to imagine the sheer scale and complexity of the highly specialised attributes offered by the inner city could be replicated in the suburbs – much less the outer suburbs – within the foreseeable future. The inner city is focussed on the CBD and in almost every city in the world, the number of jobs in the city centre is an order of magnitude larger than any suburban centre (Atlanta is possibly the sole exception). In Australia, the centre offers the cream of corporate jobs.

The importance of proximity to the CBD in explaining the special character of the inner city is demonstrated by the fact walking’s share of work trips plummets from 13% in the inner city to just 2% immediately one locates in the adjacent inner suburbs. This share is only marginally better than the outer suburbs.

Will building at higher densities and providing better public transport in the outer suburbs significantly lower the incidence of obesity? Not likely. Even if all outer suburban dwellings were townhouses, the incentive to walk is much lower if there’s no CBD, cultural precinct, river, beach, historic buildings, hundreds of cafes, and hundreds of thousands of jobs to walk to. Perhaps most importantly, the outer suburbs don’t have the constraints on driving and parking that often make walking or public transport a superior alternative in the inner city. Read the rest of this entry »

Is it healthy to assume correlation means causation?

Posted: July 11, 2011 | Author: | Filed under: Cars & traffic, Education, justice, health | Tags: , , , , , , , | 4 Comments

Association of obesity trend in the US with vehicles miles travelled (left) and with Justin Wolfer's age (right)

The link between the physical environment and health outcomes like obesity is fraught. The Victorian Legislative Council’s Environment and Planning References Committee should bear this in mind as it goes about its new inquiry into the contribution of environmental design to public health.

The Committee might want to start with the first chart in the accompanying exhibit, which comes from a recent issue of The Economist and purports to show that obesity has increased in the US in line with the increase in miles driven over the last 15 years. The chart is based on work done by researchers at the University of Illinois who found “a striking correlation between these two variables – but with a large time lag……This near-perfect correlation (99.6%) permits predictions about obesity rates”.

Expatriate Australian economist and Wharton business school Assoc Professor, Justin Wolfers, points out the folly of this claim. It is, in his words, a “nonsensical correlation”:

When you see a variable that follows a simple trend, almost any other trending variable will fit it: miles driven, my age, the Canadian population, total deaths, food prices, cumulative rainfall, whatever.

To demonstrate his point, Professor Wolfers prepared the second chart showing an even better correlation between changes in obesity over the period and changes in his age – he didn’t even need to resort to a time lag to get such a good fit! He acknowledges The Economist offered the customary caveat that correlation does not equal causation but this chart, he says, is so completely unconvincing as to warrant a different warning: “Not persuasive enough that you should bother reading this article” (in the interests of balance, here’s The Economist’s subsequent response to Professor Wolfer’s charge).

This exchange highlights a problem with much of the research that purports to show the physical environment — particularly density and/or public transport access —  has a strong effect on health-related variables like obesity. There’s plenty of evidence of correlation but not much evidence of causation. There’s no doubt obesity is inversely related to both density and access to public transport, but if it turns out these aren’t the underlying drivers of obesity then the economic cost of misdirected policies could potentially be significant.

There are special reasons why it’s hard to establish causation when dealing with real life infrastructure projects and transport/land use programs. These British epidemiologists reviewed 77 international studies examining the effectiveness of policy interventions to reduce car use. They concluded the evidence base is weak, finding only 12 were methodologically strong – and they mainly involved relatively small-scale initiatives like providing better information about travel options or direct financial incentives to reduce driving (incidentally, only half of those 12 actually worked i.e. reduced car use). Read the rest of this entry »

Does concern for the environment drive public transport patronage growth?

Posted: June 27, 2011 | Author: | Filed under: Public transport | Tags: , , , , , , , , , | 7 Comments

Factors affecting public transport patronage growth, 2002-07, Melbourne (DoT)

According to a recent paper, research by the Victorian Department of Transport (DoT) suggests concern for the environment and a healthy lifestyle is a key driver of the recent surge in public transport patronage in Melbourne.

DoT initially concluded that the primary drivers of growth over the period 2002-07 were population growth, higher petrol prices and growth in CBD jobs (see exhibit). Neither traffic congestion nor public transport service quality appeared to play a significant role.

However a large proportion of the patronage increase on trains – equivalent to about 40,000 extra daily passengers – was not explained by the variables and/or the elasticities that DoT assumed in its modelling. This unexplained increase is labelled “Other factors” on the exhibit.

Some research undertaken by Dot and Metlink suggested it might possibly relate to attitudinal factors. Of the top eight reasons given by respondents for reducing their vehicle use, environmental concerns and health & fitness ranked equal second behind petrol prices, but ahead of parking costs.

DoT subsequently undertook a telephone survey of 1500 Melburnians aged over 16 years, asking them about their attitudes to travel options and their existing travel patterns. Using cluster analysis, the researchers identified six main “attitudinal segments”:

Public transport lifestylers (19%) – “Using public transport as much as possible is just the right thing to do. Apart from being a part of my basic day to day life, it has the advantage of being better for the environment when compared to other transport modes”

Public transport works for me (17%) – “I value the time I spend on public transport. I get things out of using public transport that I wouldn’t with other modes”

Public transport rejecters (18%) – “I wouldn’t use public transport even if it was free”

Car works for me (16%) – “Car is the most convenient and useful way for me to get around. It’s not that I have a big problem with public transport; it’s just that it doesn’t suit me as much”

Agnostics (15%) – “I’m just not all that interested in the matter of how I get around. Some people are car people and some like public transport, but I’m not overly fussed either way. If you changed the public transport system, I probably wouldn’t even notice”

Convertibles (15%) – “I use my car mainly but am actually pretty open to using public transport more….but it will need to improve before I do”

Thus according to this research, nearly a fifth of Melburnians are now Public transport lifestylers who “align themselves with public transport due to a strong belief in environmental and sustainability issues, as well as a desire to live a healthy lifestyle”. What’s surprising is that all six segments have almost no (significant) relationship with age, gender, income, education or distance from the CBD e.g. the large Lifestylers segment is not just made up of inner city Greens voters.

While respondents in this segment don’t necessarily all use public transport, the paper concludes that “the results strongly point to attitudinal change having played a significant role in recent patronage growth”.

I’d like to, but I don’t buy the implication that this attitude is a major independent driver of patronage growth. My interpretation is that there’s a cluster of people who have green attitudes and not surprisingly also have a positive attitude to public transport. But I don’t think they’d use public transport in significantly greater numbers if it took longer or was more expensive than the alternatives. They’d use public transport for the same reasons most people do – because for some trips it’s cheaper and/or faster than the alternatives. Read the rest of this entry »

Is commuting (very) bad for you?

Posted: September 8, 2010 | Author: | Filed under: Cars & traffic | Tags: , , , , | 6 Comments

Let me say from the outset that I’ve long been sceptical about some of the methods used by Richard Florida, celebrated author of The Rise of the Creative Class. And I’m not the only one – this review of his book by Edward Glaeser is written with a velvet glove but packs an iron fist.

So it’s not surprising I’m unimpressed by Commuting is very bad for you, written by Florida for last month’s issue of The Atlantic. He gets it completely wrong and provides a lesson in the dangers of only seeing what you want to see.

Florida seizes on a survey of 173,581 working Americans which he claims shows that those with longer commutes suffer higher levels of back pain, higher cholesterol and higher obesity. It also shows, he says, that commuting takes a toll on emotional health and happiness – those who commute more worry more, experience less enjoyment and feel less well-rested.

Commuting by car is so bad it’s up there with smoking:

“commuting is a health and psychological hazard, not to mention the carnage and wasted time on our over-clogged roads. It’s time to put commuting right beside smoking and obesity on the list of priorities for improving the health and well-being of Americans”.

The trouble is the data he cites doesn’t support these conclusions. A proper reading of the two tables from his article (I’ve reproduced them above) indicates there’s very little relationship between commute time and health. Read the rest of this entry »

London in the time of cholera

Posted: June 24, 2010 | Author: | Filed under: Education, justice, health, Infrastructure | Tags: , , , , , , , , | 2 Comments

I’ve just read The Ghost Map by Steven Johnson. This extraordinary book, which nominally chronicles the campaign of physician Dr John Snow to persuade Victorian England that cholera was caused by contaminated water rather than noxious odours, also takes the reader on long and fascinating asides into topics like how living at density selected for alcohol-tolerant genes.

Deaths from cholera, Victorian London

As this article points out, large cities in all parts of the world used to be very dangerous places where the very proximity of humans directly led to disease and death.

I already knew the basics of John Snow’s battle with the established order and his famous map of Broad Street from TV programs and the odd book, like Mathew Kneale’s excellent novel about a Victorian hydraulic engineer, Sweet Thames.

But the particular value of Stevenson’s take on London’s cholera epidemic is the attention it gives to the broader circumstances of the times and the way he burrows deeply into the underlying social, medical and technological issues.

He talks, for example, about how humans living at close quarters historically addressed their vulnerability to polluted water by drinking alcohol instead (notwithstanding it is itself poisonous and addictive). Nothing new about that perhaps, but what is interesting is how the desire to live at higher density gradually selected for genes that could tolerate alcohol: Read the rest of this entry »