The co-benefits for health of investing in active transportation

Amid growing concerns about the effect of increasing levels of obesity and physical inactivity, climate change, population growth, increased traffic congestion and declining oil supplies, many sectors are now promoting active transportation as an alternative to driving motor vehicles.¹ While the outcomes sought range from improved health and traffic management through to environmental protection and the mitigation of climate change, promoting active transportation is increasingly recognised as a way to advance multiple agendas.

Active transportation includes travel by foot, bicycle and other non-motorised means (e.g. foot-powered scooters)² and it often forms part of a trip chain for public transport users.³ A number of reviews emphasise the importance of active transportation from health, economic, social, environmental and traffic management perspectives.^4–11 They highlight environmental interventions that would facilitate a shift from motor vehicle-dependent suburbs to communities accessible by active modes, supported by high quality public transport (Box 1).

Despite this evidence, there remains some distance between theory and practice. This paper seeks to contribute to the debate by discussing the health benefits and co-benefits of investing in policies and interventions to increase active transportation.

Box 1. 

Building the habitual use of active transport into daily routines is one means to increase physical activity.^2,5,10 Yet active transportation has rapidly declined in most developed countries over the past 3 decades.^12–17

Globally, physical inactivity ranks second only to tobacco as a behavioural risk factor contributing to the burden of disease,¹⁸ and is a major risk factor for numerous chronic diseases and their determinants (e.g. cardiovascular disease, diabetes, colon and breast cancer and mental health).¹⁹ Physical inactivity globally causes about 1.9 million deaths each year,¹⁸ and in Australia alone over 13 000 deaths each year.²⁰ Worldwide 60% of adults²¹ and approximately half of Australian adults are insufficiently active to benefit their health.²² Furthermore, physical inactivity and sedentary behaviour are independent risk factors for obesity.¹⁹ Globally, an estimated 20 million children and 1.3 billion adults are either overweight or obese,²³ as are two-thirds of men, one-half of women²⁴ and one-fifth of children in Australia.²⁵

The societal benefits of even a modest increase in those who are physically active could be large. For example, a five-percentage point increase in the proportion of people doing 30 minutes each day of moderate activity could save around 600 Australian lives per year, with significant savings to the health system.²⁶ A longitudinal study of Scandinavian adults found that, after adjustment, mortality rates in workers who cycled to work were 28% lower than others.²⁷ Similarly, a Chinese study found a 20–50% lower risk of premature mortality in women who regularly exercised or cycled for transportation.²⁸ A British study identified that children who walked or cycled to school were fitter than those who travelled by bus or car, with fitness 30% higher in boys who cycled and seven-fold higher in girls.²⁹

Increasing physical activity levels is also an essential component of interventions required to combat obesity.²¹ A recent study of walking, cycling and obesity levels in Europe, North America and Australia found an inverse relationship between population active transportation and obesity levels, providing additional support for the benefits of promoting active transportation.³⁰

Other health benefits would follow if vehicle miles travelled could be reduced. Motor vehicle transportation reduces air quality and contributes to the risk of respiratory diseases (e.g. asthma) and a range of chronic diseases, including cardiovascular disease.^31,32 In Australia, 1% of the burden of disease and injury is attributed to urban air pollution.²⁰

Urban air pollution varies by location, with particulate matter accumulating at traffic lights where flows are interrupted and vehicles idle. Pollution is, therefore, concentrated near major transport arteries, which are heavily trafficked and often congested.³³ Studies emphasise that those living on or near busy roads (within 300 metres) are exposed to significantly higher levels of pollutants.^34,35 Transport mode choice also influences pollutant exposure. Counter intuitively, vehicle drivers and their passengers may inhale up to 18 times more air pollution than those outside the vehicle,^36,37 even compared with cyclists on busy streets.³⁸

Beyond these significant health impacts, promoting active transportation confers numerous other social, environmental and economic benefits.

Pedestrian and cycling-friendly neighbourhood designs can facilitate incidental contacts between neighbours and appear to foster social capital (i.e. social networks, norms and trust).^39,40 Numerous studies show positive associations between social capital and physical and mental health, and health promoting behaviours.^41–43 Social capital may promote positive social norms while simultaneously controlling antisocial behaviours that can fuel feelings of insecurity.⁴²

Increased pedestrian traffic also has the potential to influence neighbourhood safety by generating natural surveillance. Jane Jacobs asserted that urban environments with diverse land-uses would increase public safety and minimise fear by creating lively streets, monitored by local business proprietors and residents.⁴⁴ Although greater pedestrian numbers can increase public nuisance crimes (e.g. littering, drug sales), pedestrian traffic appears protective against serious personal crime, which typically occurs when pedestrians (and, therefore, surveillance) are scarce.⁴⁵

The provision of walkable neighbourhoods, with frequent accessible public transport is also an important strategy to limit ‘transport poverty’ (e.g. households without access to public transport).⁴⁴ It also prevents marginalisation of other vulnerable subgroups with restricted mobility (e.g. children, older people and people with disabilities).^46,47

Motorised travel is dependent on oil and is responsible for almost half the world’s oil use.¹ Over-reliance on fossil fuels is a concern because of its impact on greenhouse emissions⁴⁸ and because it is a diminishing energy source. Globally, there is a need to diversify how populations are mobilised⁴⁹ to mitigate declining oil supplies. While a shift to energy efficient vehicles is one part of the solution, a more comprehensive approach is required that also involves reducing vehicle miles travelled and increasing the transport choices available to people.

Motor vehicle travel can be detrimental to environmental health.¹ In 2004, it was estimated that around 17% of carbon dioxide emissions associated with global energy use were from road transport.⁴⁸ Transport emissions are rising faster than emissions from other sectors and are projected to be 80% higher than current levels by 2030.⁴⁸ Moreover, personal motor vehicles are said to consume more energy and emit more greenhouse gas emissions per passenger-kilometre than other rail and road transport modes.⁴⁸ Vehicle-generated greenhouse gas emissions are key contributors to global warming and climate change, making them important drivers for action.

Ewing and colleagues recently lamented the futility of global warming solutions that do not curb vehicle miles travelled.⁵⁰ Citing the United States of America (USA) policy to prioritise increasing fuel efficient cars and reducing fuel’s carbon content, they argued this policy overlooks vehicle miles travelled, the most important contributor to emissions.⁵⁰ They estimated that if 60% of new US housing growth occurred in transit-oriented developments, about 85 million metric tonnes of CO₂ could be saved annually by 2030.⁵⁰ Thus, while restraining personal vehicle ownership and use need to be policy priorities,⁴⁸ this can only succeed if land use and transportation investments in pedestrian, cycling and transit infrastructure are prioritised.

Another compelling reason for curbing vehicle miles travelled is traffic congestion. Internationally, traffic congestion is a growing concern, given that over half the world’s population already lives in cities; by 2030, it is predicted that the urbanised population will reach five billion.⁵¹ Given the link between traffic congestion and air pollution, the rapid motorisation and urbanisation of developing countries are troubling. For example, between 2000 and 2020, Chinese emissions of carbon hydroxide, dioxide (CO₂) and monoxide, sulphur dioxide, volatile organic compounds, and nitrous oxide are predicted to rise up to 20-fold.⁵²

From a health perspective there are economic benefits associated with investing in active transportation. In Australia, recent estimates indicate the direct and indirect costs to the Australian economy are $13.8 billion for physical inactivity,⁵³ and the direct costs $21 billion for obesity and overweight.⁵⁴ The annual costs of obesity and physical inactivity will continue to grow if current levels continue unabated.^55–58

In New Zealand (NZ), Woodward modelled the impact on the health budget of a 5% increase in bicycle trips of less than 7 km (equivalent to levels in 1980).¹⁷ After accounting for additional costs associated with cycling injuries and fatalities, he estimated the annual net health savings amounted to $200 million, or around 1.6% of NZ’s annual health budget. A comparable impact in Australia would save around $1.7 billion on Australia’s 2007–08 health expenditure.⁵⁹

Changes to neighbourhood design could also produce benefits for the local micro-economy. Increasing population densities and boosting local pedestrian and cycling traffic flows can increase the economic viability of cafes and corner stores, and improve access to jobs and services without increasing congestion or vehicle emissions.⁶

As depicted, investment in active transportation has the potential to produce substantial co-benefits across multiple sectors,⁶⁰ including health.^61,62 When benefits across multiple policy areas are considered concurrently, the term co-benefits is used. For example, the City of London’s congestion tax not only reduced traffic by 30%, and CO₂, NO_x (refers to NO and NO₂) and large particulate emissions by 16–20%, it also increased walking and cycling.⁶³

Yet to date, relatively few studies have quantified the co-benefits of different approaches to changing modes of transport and the impacts on CO₂ and health.⁶⁴ Using Comparative Risk Assessment methods, Woodcock and colleagues estimated the effect of alternative transportation scenarios on health and carbon emissions, compared with business-as-usual.⁶⁴ Table 1 summarises the results for London, indicating the co-benefits that could be derived from implementing strategies that increased both lower-emission motor vehicle use and active transportation (i.e. a two-fold increase in distances walked and an eight-fold increase in distances cycled from a very low base). Compared with a strategy focused solely on lower emission vehicle use, a combined intervention would almost double reductions in greenhouse emissions in London and would substantially reduce premature deaths and years of life lost to disability.

Table 1.  Anticipated environmental and public health impacts of different land transportation strategies to reduce greenhouse gas emissions in London (adapted from Woodcock et al. 2009)⁶⁴

Nevertheless, to have an impact, active transportation requires land-use planning and infrastructure investment that creates pedestrian and cycling-friendly communities.^62,65 Numerous studies now point to the importance of the built environment as a determinant of active transportation.^2,3 Moreover, studies have recently begun to demonstrate the effectiveness of infrastructure investments in changing behaviour,⁶² and their cost effectiveness as a public health^66,67 or transport and health⁶⁸ intervention. Ignoring the implementation of complementary strategies (e.g. congestion pricing, increased transit use) or co-benefits, Ewing and colleagues⁶⁵ recently estimated that a change in land-use planning in the USA (from urban sprawl to compact development) could reduce vehicle miles travelled by 20–40% and transportation greenhouse emissions by 7–10% by 2050.

However few studies have comprehensively considered the co-benefits of land-use and transportation planning, including the co-benefits of strategies required to avoid negative impacts. For example, despite the benefits of compact urban development, strategies may be required to mitigate heat island effects (e.g. urban tree plantings, building living and lighter roofs) that could beneficially affect health. Moreover, in economic analyses, consideration of co-benefits is embryonic,⁶⁸ yet this approach could substantially increase benefit-cost ratios associated with infrastructure investment.⁶⁷ Together these are fruitful lines of future enquiry for multidisciplinary research teams that could provide evidence to help prioritise strategies.

As societies confront the economic, social and environmental effects of climate change, population growth traffic congestion and the burden of chronic disease, there is a unique opportunity to view the benefits of active transportation through a multi-sector lens. This paper shows that by taking a co-benefits approach to transport policy-reform, there is an opportunity to minimise carbon emissions and improve health. Studying the co-benefits of policy-options however is at the nascent stage. There are enormous opportunities to extend this approach to examine the co-benefits of active transportation encompassing broader perspectives e.g. reducing traffic congestion to achieve broader societal objectives related to socially and environmentally sustainable communities.

More multidisciplinary research is required that informs ‘joined-up’ policy solutions that cut across multiple policy agendas. The language of co-benefits is useful as it helps breaks down policy silos and presents additive (rather than discrete) benefits that could be incorporated in economic analyses to assess cost-effective strategies. Moreover, it could inform debate and facilitate assessment of policy alternatives to optimise outcomes for the community. Thus, articulating co-benefits should be at the forefront of future policy-reform discussions. An active transportation intervention not only tackles climate change, it could also deliver powerful co-benefits related to preventive health, social capital, traffic congestion and the economy.