Over half of the world's population live in cities, and rapid urbanisation is only expected to increase in the coming years. By 2050, large cities in the USA, China and India are predicted to see their populations increase by 33 per cent, 38 per cent and 96 per cent respectively. Population growth in cities means increasing demands on transport systems.
What health gains could be achieved if cities shifted from private car use to cycling and walking? What if a "compact city" model was promoted, where distances to shops and facilities, including public transport, are shorter and within walking distance?
The University of Melbourne is leading the study, which has some revealing results.
The proposed could achieve "significant reductions" in non-communicable diseases such as cardiovascular disease and diabetes -- as well as increasing physical activity and reducing pollution. Importantly, in cities with high levels of private car use such as Melbourne, researchers say that promoting walking and cycling must be matched by improvements to infrastructure that separate motorised transport to protect cyclists and pedestrians from road injuries.
Sprawling residential developments in the USA, Australia and New Zealand limit the ability of people to walk or cycle in their daily commute and make public transport expensive to deliver. Private car use has increased dramatically in Brazil, China and India leading to declines in physical activity, increases in air pollution and increased rates of road death and serious injury, all of which combine to increase overall levels of chronic disease and injury.
"With the world's population estimated to reach 10 billion people by 2050, and three quarters of this population living in cities, city planning must be part of a comprehensive solution to tackling adverse health outcomes," says University of Melbourne's Professor Billie Giles-Corti.
City planning was key to cutting infectious disease outbreaks in the 19th century through improved sanitation, housing and separating residential and industrial areas. Today, Professor Giles-Corti says, there is a real opportunity for city planning to reduce non-communicable diseases and road trauma and to promote health and wellbeing more broadly.
Encouraging walking, cycling and public transport use -- while reducing private car use -- is the goal. Ways to do this identified in the study include having shops and services within walking distance, a mix of employment and housing across the city, reducing the availability and increasing the cost of parking, infrastructure that supports safe walking and bicycling, open spaces, reducing distance to public transport, and making neighbourhoods safe, attractive and convenient for public transport.
"We concluded that focusing on walking and cycling infrastructure alone is critical but not enough -- to create cities that promote health needs joined-up policies and input across multiple sectors: land use, transport, housing, economic development, urban design, health and community services, and public safety," adds Professor Giles-Corti.
Professor Mark Stevenson from the University of Melbourne designed a 'compact cities model' where land-use density was increased by 30 per cent, average distance to public transport reduced by 30 per cent, and diversity of land-use increased by 30 per cent. They also factored in a 10 per cent shift from private cars to either cycling or walking -- a target similar to that of policies in many European cities such as Zurich.
These targets were selected on the basis that they are pragmatic in most cities -- for instance in Melbourne approximately 14 per cent of private motorised vehicle trips are for trips of less than 5km so a shift from car to active commuting (walking combined with public transport) for example would be feasible.
The model was applied to six cities: Melbourne, London, Boston, Sao Paulo, Copenhagen and Delhi. Health gains were predicted in all cities, with the greatest effect on reducing rates of cardiovascular disease. In addition, all cities saw increases in physical activity and reductions in air pollution from transport emissions.
In Melbourne, the model led to an estimated reduction of 19 per cent in the burden of cardiovascular disease and 14 per cent in the burden of type 2 diabetes. The model also predicted an increase in road traffic incidents for cyclists and pedestrians -- an increase of approximately 6 per cent in Melbourne (257 additional road injuries and 10 deaths per year). However, separating pedestrian and cycling from cars was found to offset the increased road injuries and deaths.
"The effect of interventions that encourage cycling and walking was particularly evident in highly motorised cities such as Melbourne, London and Boston, and underscores the importance of transport policies, pricing and regulation that encourage active transport via cycling, walking and public transport while discouraging private car use," says Professor Stevenson.
"These changes also need to be matched by improved pedestrian and cycling infrastructure to protect cyclists and pedestrians. Our study shows that these changes at city level could lead to real health gains."
Several cities have made progress in increasing walking and cycling including London, Stockholm and Bogota -- for instance, motor vehicle traffic volumes across London decreased by 7 per cent between 2004 and 2014 and cycling has increased, despite a growing population. But the researchers warn that much more should be done to improve the health of cities.
"City planning policies can affect health, both positively and negatively. Sadly, it is clear that many city leaders around the world are not applying the lessons of research to make cities as healthy as possible," says Professor James Sallis from the University of California.
"A continuing challenge is to improve the communication of this evidence to city leaders and find incentives for them to seek out and apply the evidence. A major incentive is that designing cities for health and active transport, rather than automobile-dependence, also makes the cities more environmentally sustainable helping cities to achieve the UN's Sustainable Development Goals."
Peter Newman, Professor of Sustainability at Curtin University calls the study "a powerful new statement" on the need for cities to reduce automobile dependence.
"The evidence has been mounting for some time that suburbs built around the car are not healthy and the health profession have been quite slow at reaching the need to stop urban sprawl, but I welcome it," he says. "Cities which are walkable are more wealthy, as well as being more healthy and using less fuel. We show that car use and GDP per capita are now decoupling".
"The days of urban sprawl are over. We must regenerate our cities and ban any further outward sprawl."
Jago Dodson, Professor of Urban Policy and Director at the Centre for Urban Research says the study shows a clear need for improved urban policy to ensure cities are healthy and sustainable.
"The era of car-based urban transport policy has been a failure for both the health of urban dwellers and for the amenity and liveablity of cities," he says. "This research signals the need for a complete reversal of current Australian urban transport policy to take the resources wasted in building infrastructure for cars and dedicate them to public transport, accompanied by walking and cycling infrastructure".
"Moreover a rethink of our transport planning institutions is needed -- Australia's transport agencies were designed for the automobile age, they need to be reconfigured for the new era of sustainable and active transport."