The sustainable transport movement, part of the environmental movement, has gradually gained in force over the last decade and a half, and has in the process started to shift the emphasis in public spending and actions away from building and supply, to management and demand. The values of respect for the environment and prudent use of natural resources are central, with varying degrees of urgency expressed by different actors and interests. That said, it is still very much a minority movement and most actual expenditures in the sector are determined by criteria other than sustainability.
What is clear is that sustainable transportation mainly refers to human behavior, not to technology. In that sense, a behavioral approach considers not only a set of non-polluting and human scaled green transport choices, regardless of the means and technology used, but also a set of reinforcers both individual and social to promote these choices.
The term Sustainable transport, also commonly referred to as Sustainable Transportation or Sustainable Mobility, has no formal definition, but is a logical follow-on from the earlier term Sustainable Development whose origins in turn were the 1987 Our Common Future (1987, World Commission on Environment and Development of the United Nations). Thus it is often defined in words such as this: “Sustainable transportation is about meeting or helping meet the mobility needs of the present without compromising the ability of future generations to meet their needs.”
The term is also used to describe all forms of transport which minimize fuel consumption and emissions of carbon dioxide and pollutants. It can refer to public transport, car sharing, walking and cycling as well as technology such as electric and hybrid cars and biodiesel and Personal Rapid Transit and other green transport. The term has been adopted by the British and Australian national and local governments, and both the phrase and the concepts have now spread around the world.
One early and often cited definition offered back in 1994 by the Organization for Economic Cooperation and Development (OECD) defined sustainable transport as: "Transportation that does not endanger public health or ecosystems and meets mobility needs consistent with (a) use of renewable resources at below their rates of regeneration and (b) use of non-renewable resources at below the rates of development of renewable substitutes". This provided a conservative benchmark view of what sustainable transport is all about which is still often put forward in the public debate.
The Canadian Centre for Sustainable Transportation defines a sustainable transportation system as one that:
The New Zealand Ministry for the Environment offers a practical definition of transport that is 'more sustainable' (but still falls short of being truly sustainable in the long term). This definition extends the scope of sustainable transport to include the layout of cities and the balance of transport investments, and defines it in terms which more accessible to business, communities and government:
A shorter definition by the Sustran network does a good job in one paragraph of summarizing the consensus view from the vantage of transport activists and many NGOs:
The World Business Council for Sustainable Development uses the term "sustainable mobility", and defines this as "the ability to meet the needs of society to move freely, gain access, communicate, trade, and establish relationships without sacrificing other essential human or ecological values today or in the future.
This definition encompasses the following dimensions:
The automotive and energy industries increasingly use the term "Sustainable Mobility" to describe and promote their technology developments, primarily in the areas of new motive and engine technologies and advances. The impact of these advances, however, requires at least one or two decades to make a perceptible difference in terms of sustainability, and may not have benefits for the groups of people who benefit most from sustainable transportation policies.
In general the phrase is used to encourage more attention to green transport options such as improved provision for cycling, walking, public spaces, rail and other forms of public transport, together with measures to reduce car use, especially in central areas. It can also cover “movement substitutes” such as telework, telecommuting and smart growth redevelopments which improve the mix of activities and reduce the need for motorized transport.
Sustainable transport, with its focus on people, differs from Transportation Demand Management, which is a complementary effort to manage transportation systems in ways that reduce the impacts of single occupancy commuter travel and improve the provision of other transport choices.
Yet the cities that have invested most heavily in car-based physical transportation infrastructures are now experiencing the most unsustainable levels of traffic and resource use. This pattern is observable globally; an average U.S. urban dweller uses 24 times more energy annually for private transport as a Chinese urban resident, and around five times as much as a resident of a European city of equal economic prosperity. Within the United States, residents of sprawling cities make more frequent and longer car trips, while residents of traditional urban neighbourhoods make a similar number of trips, but travel shorter distances and walk, cycle and use transit more often.
Cities with overbuilt roadways have experienced unintended consequences, linked to radical drops in public transport, walking, and cycling. In many cases, streets became void of “life.” Stores, schools, government centers and libraries moved away from central cities, and residents who did not flee to the suburbs experienced a much reduced quality of public space and of public services. As schools were closed their mega-school replacements in outlying areas generated additional traffic; the number of cars on US roads between 7:15 and 8:15 a.m. increases 30% during the school year.
One of the first international organizations to have a closer look at the links between transport and sustainability from the vantage of government policy was a small international working group led by Peter Wiederkehr at the OECD in 1994, that agreed that a new policy approach is needed which places environmental criteria up front along with other policy goals. Recognizing this need, the OECD initiated in 1994 an international project to define and chart a path towards Environmentally Sustainable Transport (EST) The overall objectives of the EST project are to provide an understanding of EST, its implications and requirements, and to develop methods and guidelines towards its realization. The core of the EST approach was to develop long-term scenarios and identify instruments and strategies capable of achieving it. To this end the OECD organized with the Government of Canada the 1996 International Conference: Towards Sustainable Transportation in Vancouver, Canada. One result of this were the 1996 Vancouver Principles towards Sustainable Transportation. (The OECD project shut down its operation in July 2004, though the members of the original working group continue to communicate and collaborate at the specific project and policy level under the leadership of the Austrian Federal Ministry of the Environment.)
As governments increasingly recognise sustainability as a core guiding principle, the need for more sustainable transport systems has been officially recognised in the transport strategies of the United Kingdom and of New Zealand.
Sustainable transport policies have their greatest impact at the city level. Outside Western Europe, cities which have consistently included sustainability as a key consideration in transport and land use planning include Curitiba, Brazil, Portland, Oregon and Vancouver, Canada.
Many other cities throughout the world have recognised the need to link sustainability and transport policies, for example by joining Cities for Climate Protection
Sustainable transport is fundamentally a grassroots movement, albeit one which is now recognised as of citywide, national and international significance.
Whereas it started as a movement driven by environmental concerns, over these last years there has been increased emphasis on social equity and fairness issues, and in particular the need to ensure proper access and services for lower income groups and people with mobility limitations, including the fast growing population of older citizens. Many of the people exposed to the most vehicle noise, pollution and safety risk have been those who do not own, or cannot drive cars, and those for whom the cost of car ownership causes a severe financial burden.