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WHO report urges greater attention to improved land use, rapid transit, cycling and walking to achieve health co-benefits from transport GHG emissions mitigation

Urban density is one of the most important determinants of car use and transport-related energy consumption in cities. Source: WHO report. Click to enlarge.

Among strategies to reduce CO2 emissions in the transport sector, a shift to active transport (walking and cycling) and rapid transit/public transport combined with improved land use can yield much greater immediate health “co-benefits” than improving fuel and vehicle efficiencies, according to a new WHO (World Health Organization) report.

These strategies need more systematic study by the Intergovernmental Panel on Climate Change (IPCC)i in the assessment of transport mitigation measures, according to the report, Health co-benefits of climate change mitigation - Transport sector, released this week during the United Nations Framework on Climate Change Conference of the Parties (COP-17) in Durban, South Africa.

The report reviewed more than 300 studies on health outcomes from different types of land transport systems in a “scoping exercise” designed to identify those mitigation measures most closely associated with specific health co-benefits or risks.

The review is the latest product of WHO’s Health in the Green Economy initiative, which is considering available evidence on health impacts from climate mitigation strategies for key economic sectors, as reviewed by the UN’s Intergovernmental Panel on Climate Change.

The IPCC’s global assessment of mitigation options for the transport sector places the greatest emphasis on the mitigation potential of improving carbon efficiencies for private vehicles and fuels. In contrast, the WHO review found a stronger, and more positive, association with health benefits from rapid transit and dedicated walking/cycling systems—measures which are covered by IPCC, but not as systematically and with little note of health issues.

We have looked at the IPCC assessment through the lens of public health and come up with quite a different reading. Public/rapid transport and safe cycling and walking are the prototype of a transport system that is good for health; it so happens that these are good for climate too.

—Dr. Carlos Dora of WHO’s Department of Public Health and Environment

Among the other key messages of the report:

  • Potential health gains of a shift from private motorized transport to walking, cycling and rapid transit/public transport include reduced cardiovascular and respiratory disease from air pollution, less traffic injury and less noise-related stress. In addition, large benefits are expected from increased physical activity, which can prevent some cancers, type 2 diabetes, heart disease and other obesity-related risks. Improved mobility for women, children, elderly and the poor, who have less access to private vehicles, enhances health equity.

  • Shifting from gasoline to diesel vehicles could increase emissions of health-damaging small particulates (PM10, PM2.5). IPCC’s assessment finds diesel vehicles have potential to reduce transport’s CO2 emissions. However, diesel engines typically emit higher concentrations of small particulates. In Europe, large shifts to diesel vehicles over the last decade are regarded as a cause of stable (but not lower) urban PM10 levels—despite the introduction of cleaner diesel technologies.

  • Transport-related health risks now cause the deaths of millions of people annually. For example, WHO estimates that urban air pollution (much of it transport-generated) kills some 1.3 million people annually. Additionally, traffic injuries kill another 1.3 million people every year, mostly in low- and middle-income countries. Some 3.2 million deaths annually are due to physical inactivity.

Overarching goals of healthy transport include: (a) reduced deaths and disease generally from transport-generated air, noise, and water pollution; (b) reduced exposures of disadvantaged groups to excessive transport-related injuries and health risks; (c) safer and more efficient access, especially for vulnerable groups, to jobs, schools, services and social opportunities; (d) increased physical activity, including through safe walking and bicycling; (e) reduced climate change emissions from transport that contribute to future, as well as present-day, health impacts.

—Health co-benefits of climate change mitigation—Transport sector

These goals can be achieved via four main strategies, according to the report:

  1. Compact land-use systems that increase density and diversity of uses.

  2. Investments in, and prioritization of, transport networks for pedestrians and cyclists.

  3. Investments in, and prioritization of, transport networks for rapid transit/public transport.

  4. Transport engineering and traffic-calming measures that protect vulnerable road users from motorized transport’s hazards.

The report highlighted a number of policy tools to support health-oriented strategies:

  • Health impact assessment that identifies and addresses health co-benefits and risks at the planning stage, as well as measures to improve health and reduce health inequities.

  • Strengthened land-use/transport planning, codes and enforcement; for example, ensuring universal access to safe cycling and pedestrian routes and to rapid transit/public transport for basic routines.

  • Development and monitoring of healthy transport performance criteria and indicators, including better indicators for active travel/physical activity; use of non-motorized modes and public transport; air/noise pollution exposures; pedestrian injuries; and mobility/access.

  • Economic evaluation and assessment methods that fully account for the health co-benefits of walking, cycling and rapid transit/public transport use.




Has anyone noticed that the 11 cities with the least population density are all in USA followed by cities located in Canada and Australia?

This strangely correlates almost exactly with per capita pollution emissions where those three countries also excel.

Lower population density = higher (per capita) pollution emissions?

Is there a way to reverse that equation?


The energy graph is stunning.

The US average use is ~3X(3 times) Europe. Europe is ~3X China.

How is Atlanta ~2X LA? With Dallas/Ft. Worth a 100 miles across, good thing it's kept off the graph.

The US can't point fingers at China coal when we use ~9 times more energy per person every day.


Kelly....that is really something that most Americans do not want to see or hear about because it they could go from hero to zero with regards to efficient use of energy and pollution emissions. I guess that it was OK as long as they could get ultra cheap crude oil and other very low cost energy sources. When Oil went from about $1/barrel to $100+/barrel it made their city sprawl very costly.

I watched a recent documentary on Detroit City last night and the many square miles of abandoned houses, streets and services has a third world look to it. Who would have guessed that a large USA prosperous city could deteriorate that much.


I saw a strange but high potential 28-ft wide city/suburban multi unit electrified bus, running on high legs on rails. Two lanes of cars drive under it, as you would under a covered bridge. Theses buses never have to face traffic jams, they just drive over them. Being as wide as a jumbo jet, they can take a huge number of passengers on their high second level deck. An excellent future solution for very large cities like Beijing, and many others.

Making double use of the same city street space is a new idea.


These reports from IPCC are meaningful only to IPCC devotes. Less and less everyday.


Even Judith Curry imagines a "post-IPCC" world:



And there is this harsh realism:


fred schumacher

This push for high density habitation ignores the reality of human nature and our evolutionary history. If people actually wanted to live in such close proximity, they would do it. When given the opportunity and capability to spread out, they chose to do so.

The fact that there is only one high density metro in the U.S., New York City, is an indication of the reality that we are tropical savanna animals, accustomed over thousands of years to life in small, widely dispersed family groups. That high density cities do exist at higher rates in other parts of the world is a function of poverty, high population, and lack of space.


Fred....the automobiles and the acquired love of driving did it. It was a good solution until everybody had a car and started to drive to work with it. Huge daily traffic jams became common place. Driving downtown to work is becoming to be a costly and almost impossible time consuming task in many cities, spread out over very wide spaces. Compact city cores with XXX thousands of jobs but fewer living places created the need to travel long distances every day.

There are many solutions but they will all cost a lot to implement. Many more high speed suburban e-trains and subways would help. Re-distributing city cores (jobs) to many other smaller cities along existing highways and e-trains routes would also help. Building more high rise apartments in city cores, closer to where jobs are. Build Korean style factory cities where people live and work and study is also very effective.

Nick Lyons

@fred schumacher: Hmm.

This push for high density habitation ignores the reality of human nature and our evolutionary history.

The part about human evolution ignores the most recent part, when agriculture was invented, some tens of thousands of years ago (granted that's a blink in the history of mankind). Civilization is all about the economic and cultural benefits of cities. The sad fact is that agriculture begat cities and cities begat technology and technology begat the human population explosion such that there's way too many of us now to go back to anything like hunter-gathering. Innocence is lost, Eden is no more, you can't go home again. City life is the future for most of humanity, whether we long for the savannah or not. Sad but true.

Disclaimer: I live in Alaska, on the edge of a vast wilderness.


I would say evolutionary history shows the oposite. Humans are social animals, we find strength and comfort in numbers. In the past people actually did want to live in such close proximity but as the land could not support large numbers of hunter-gatherers they could only live in small closeknit groups. As soon as they found ways to grow more food on less land they started collecting together into towns and then cities.

fred schumacher

Research by Robin Dunbar and others has shown that the maximum number of people humans can maintain direct relationships with is about 150. That is the size of a village, a military company, a Hutterite colony.

Since the dawn of our species, anatomically modern humans, about 200,000 years ago, we have been undergoing the process of population explosion. After the invention of language, that process speeded up. We colonized the globe extremely rapidly. We invented agriculture as a necessity, a result of population exceeding the foraging carrying capacity of the land.

As Cesare Marchetti and Yakov Zahavi have shown, humans choose to budget about an hour and a quarter a day to travel, irrespective of the mode of travel. In ancient Imperial Rome, it was possible to walk from any part of the city to the Forum and back in one hour. As mode of travel increased in speed, humans could disperse to greater distances, but the travel time remained constant.

In the early 1950s, over half the jobs and retail in Minneapolis, Minnesota were downtown, which was served by a hub and spoke trolley system. Today, jobs and retail are isotropic, spread all over the Twin Cities metro area. Today's downtown Minneapolis only provides about 3% of retail.

Real estate change is an expensive way to solve a transportation problem. Making cities denser creates the need for increasing levels of formal social control. Our home community in northern Minnesota has no police in our nearest market town and only one county deputy to cover 3,000 square miles. There are more bears than people. Social control is self-regulating.

Burnsville, a Twin Cities suburb where one of my sons lives, is the same size as Manhattan, has the same area in city parks, but has 60,000 population versus 1.3 million. In addition, one-third of its area is lakes and undeveloped land allowed to remain wild. The other day, my granddaughters and I watched a buck and doe walk through the woods behind their house, followed by three wild turkeys, which came up to the sunroom windows.

Burnsville has very little concrete, compared to Manhattan. The parks have wild areas which are not manicured. Yes it is a low density community by urban standards, but it is tremendously dense compared to a rural area. However, it provides the benefits of space with concentration, and that is why it exists and why humans prefer to live that way, if they have the opportunity to do so. Attempting to squeeze people into super-dense concrete jungles is not the way humans naturally desire to live.


This is nothing new.

That same graph was also shown in the UK's Urban Task Force report "Towards and Urban Renaissance", produced in 1999, as part of an evidence base that underpinned government planning policies in the UK for bringing development back to the centre.

In principle I agree with the logic of higher density, mixed use development and good public transport but it has to be good quality and respond to people's needs for living, working and travelling.

In the UK however, planning policy has only led to 'tick box' development with an oversupply of poorly designed homes dominated by shoe box flats and a lack of decent sized family housing, simply as a way to respond to density targets than real housing needs. Maximum parking standards, instead of reducing car ownership and use has just forced more cars to be badly parked on narrow resiential streets, thus having the opposite effect of reducing vehicle dominance.

By all means higher density and mixed use are great but unlike traditional easy sprawl development, careful thought is needed for responsive policies which encourage high quality, well designed developments. As part of this process, we must realise that for travel, this can at best reduce and not replace the need for car travel. Mixing development, doesn't automatically make work a 5 minute walk round the corner, nor does it encourage friends to live closer, if they are 50 miles away, as they will be living there for there own reasons, and public transport, no matter how much investment you throw at it, will not cater for all journeys. So lets be aspirational but realistic instead of pushing ideological utopias onto people who will reject them.

Hence, people's needs to travel by car, as well as by active and public modes must be part of the solution.


The advent of near-zero cost, zero-pollution sources of energy will change some migration. People able to live sustainably, comfortably off-grid will move away from urban density to cleaner, more pristine natural areas. No longer tethered by wires, people will choose to live where they find the habitat comfortable and rewarding. An excellent evolutionary step, expanding independence while maintaining connection to the larger world.

These people will choose to live in the countryside, deserts, remote seashores, jungles, etc., making monthly or bi-weekly trips to small centers for supplies. Once again the promise of "Life, Liberty and the Pursuit of Happiness" rings possible.


Add a heat to electricity thermionic converter, a Star Trek food distributor and a matter creator/transporter and Reel$$ would be happy.


We have most of those things now. For hundreds of years people chose to live in the countryside. Up until 1930s 90% of North Americas lived on farms. Before the AGWs tried to take over the world, environmentalists were people who favored moving back to farms.

With world population projected to shrink as prosperity grows - this CAN and probably will happen. People who elect to live in the city will. Those who can telecommute or don't mind driving, will live in the rural landscape and be all the happier for it.


Many people live in the suburbs and never know many of their neighbors. That is the way they seem to like it. They do not like commuting nor traffic, but that seems to go with the package.


Detroit City is certainly in the forefront. Built for 2+ million people not so long ago, more than half have already moved out. The accelerated emigration is not caused by a preference to live in the country side but for the lack of local jobs. Over 100,000 houses are abandoned and being demolished. Complete neighborhoods will be turned into urban farms. One or two thousand lots/houses will become one farm with one house and one family employed as farm keepers at minimum salary?

This is a lot like back to the future? Farm owners will live in castles and farm keepers will do the work with survival pay.


The exodus from Detroit didn't start with a lack of jobs. There were plenty of jobs through the 1970's. It started with crime, and the Coleman Young administration which used it to conduct ethnic cleansing.


Sorry to disappoint E-P but jobs left Detroit (about one year) before people, which is normal.

From 1900 to 1950, Detroit population and jobs grew by over 600%.

The end of 1950 was the peak population with 1,849,568 and it has been dropping steadily since to a low of just below 700,000 at the end of 2010. The latest estimates are 655,000 for 2011, 575,000 for 2012, 500,000 for 2013.

Jobs have followed about the same decrease as the population with about a one year delay. Jobs went from 735,000 in 1970 to a low of 270,000 in 2010.

Factories and people have been moving out of Detroit City for the last 61 years. If over 50% of Detroit land area is converted to urban farms (and it may very well happen), the population could drop another 50% or so. Historians will have something to write about. How can a 2,000,000 people prosperous city drop to 350,000 without a Tsunami or a major Earth quake? I don't know how effective was the Coleman Young Administration but the current population is 78% African, 12% white, 8% Hispanic and 2% Others.


There was a major earthquake. It was called the 1967 riots, and there were aftershocks for decades on "Devil's Night".


Would the success or expansion/growth rate of a major city core be closely linked to its population? People and jobs will move out or in at an accelerated rate when the inherent quality of the residents changes. We are currently seeing similar effects in many quarters of our large city but nobody dares saying it.


Harvey, I do believe you just grasped HBD (human biodiversity).


We have looked at the IPCC assessment through the lens of public health and come up with quite a different reading. Public/rapid transport and safe cycling and walking are the prototype of a transport system that is good for health; it so happens that these are good for climate too. luxury apartments london

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