The agenda for cities of the future is to have more sustainable transport options available so that a city can indeed reduce its traffic whilst reducing its greenhouse gases 50 percent by 2050 (the global agenda set through the International Panel on Climate Change). For many cities the reduction of car use is not yet on the agenda apart from seeing it as an obviously good thing to do. Unfortunately for most cities traffic growth has been continuous and appears to be unstoppable.  To reduce a city’s ecological footprint and enhance the liveability of the city it will be necessary to manage the growth of cars and trucks and their associated fossil fuel consumption.

The variations in private transport fuel use across 84 cities shows that there is a very large difference in how cities use cars and petroleum fuels. Through a number of studies it has been shown that these variations have little to do with climate, culture or politics, and even income is very poorly correlated, but they have a lot to do with the physical planning decisions that are made in those cities – see especially our ‘Sustainability and Cities’ Newman and Kenworthy, 1999. There is debate about the relative importance of urban planning parameters though within the profession there is increasing awareness that sustainable transport will only happen if there is an emphasis on urban form and density; infrastructure priorities especially the relative commitment to public transport compared to cars; and, street planning especially the provision for pedestrians and cyclists as part of sustainable mobility management.

Urban Form and Density Planning

The view of New York City's skyline from the Empire State building.
New York City was named one of the most walkable metropolitans in
the U.S. by George Washington University due to its high density. Photo
credit: Aurelien Guichard via Flickr. 

The density of a city determines how close to urban activities most people can be. Very high density city centres mean that most destinations can be reached with a short walk or they can have highly effective public transport opportunities due to the concentration of people near stations. If densities are reduced but are focussed along corridors it is still feasible to have a good transit system. If however low densities are the dominant feature of a city then most activity needs to be based around cars as they alone can enable people to reach their destinations in a reasonable time. Public transport finds it hard to be competitive as there are just not enough people to justify reasonable services. Most low density cities are now trying to increase their densities to reduce their car dependence.

Density is a major tool available to planners in cities. It is best used where a city has good transit or wants to build transit as the resulting Transit Oriented Developments (TODs) are found to reduce car use per capita among its residents by half and to save households around 20% of their household income as they have on average one less car (often none). TODs are thus an affordable housing strategy as well. In the U.S., according to a 2007 study by Reid Ewing, “shifting 60 percent of new growth to compact patterns would save 85 million metric tons of CO2 annually by 2030.” TODs reduce ecological footprint in cities and undermine the kind of car-based sprawl that eats into the green agenda of cities. Thus this strategy of TODs can enable a city to put in place a clear urban growth boundary and to build a green wall for agriculture, recreation, biodiversity and the other natural systems of the green agenda. Cairo’s green belt is one attempt to do this.

If cities are dense, as in many developing cities, but they do not have adequate public transport and they allow too much traffic to develop in their streets, then they can easily develop dysfunctional transport systems. However their density will always enable them to provide viable public transport solutions if they invest in them, whereas low density cities are always struggling to provide any other options. High density means easier non-car based access but it can also mean much greater congestion whenever vehicles are used. If the vehicles in these confined spaces are poorly maintained diesel engines then very serious air pollution can result so cities need to be very serious about managing the source of such emissions.

Infrastructure Priorities--Especially Transit Planning

The relative speed of transit to traffic measures how effective public transport is in competing with the car. The best European and Asian cities for transit have the highest ratio of transit to traffic speeds and have achieved this invariably with fast rail systems. Rail systems are faster in every city in the sample by 10-20 kph over bus systems that rarely average over 20 to 25 kph. Busways can be quicker than traffic in car saturated cities but in lower density car dependent cities it is important to use the extra speed of rail to establish an advantage over cars in traffic. This is one of the key reasons why railways are being built in over 100 US cities and in many other cities modern rail is now seen as the solution for reversing the trend to the private car. The trend to electric urban rail is now called a global megatrend. Rail is also important as it has a density-inducing effect around stations which can help to provide the focussed centres so critical to overcoming car dependence and they are electric which reduces oil vulnerability.

Many cities in the world are unable to make transit politics work effectively. While major US cities such as New York and Chicago are dense and walkable, and their mayors have been lauded for their green plans and for signing onto the Mayor’s Climate Change Initiative, the mass transit systems for these cities continue to experience budget cuts. The city of Seattle, whose mayor is credited with initiating the US Mayor’s Climate Change Initiative, has struggled to implement any type of rail system. And while the State of California is a global leader on some state initiatives it has not yet developed a plan for how its heavy oil-using cities will wean themselves off their cars.

Yet across the world cities are building modern electric rail systems at vastly increasing rates as they solve the simultaneous problems of fuel security, decarbonising the economy for climate change, reducing traffic congestion sustainably, and creating productive city centres. The trend to fast electric rail in cities is now being called a Mega Trend. Chinese cities have moved from their road building phase to building fast modern rail across the nation. China is committed to building 120,000 km of new rail by 2020. Investment will rise from 155 billion Yuan (US$22b) per year in 2006 to 1000 billion per year by 2009 (US$143b), with around 6 million jobs involved; the projects are part of their response to the economic downturn. Beijing now has the world’s biggest Metro.

In Delhi the city has built a modern electric metro rail system which has developed considerable pride in their community and belief in their future. The 250km rail system is being built in various stages and will enable 60% of the city to be within 15 minutes walking distance of a station.

In Perth, Australia a 172 km modern electric rail system has been built over the past 20 years with stunning success in terms of patronage and the development of TODs; the newest section runs 80 kms to the south and has attracted 50,000 passengers a day where the bus system carried just 14,000 a day – the difference is that the train has a top speed of 130 kph and averages 90 kph so the trip takes just 48 minutes instead of over an hour by car. London, especially with its congestion tax which is recycled into the transit system, and Paris have both shown European leadership in managing the car.

While greening buildings, looking to renewable fuel sources, and creating more walkable communities are critical pieces of the sustainable city, investing in viable, accessible transit systems for cities is the most important component for them to become resilient to waning oil sources and in minimizing the impact of urban areas on climate change. Transit not just saves oil it helps restructure a city so that it can begin the exponential reduction in oil and car use so necessary for the future.

The opportunities for making major changes in a city if quality transit is a priority can be imagined but their extent is often not seen to be more than a mere slowing of traffic growth. We suggest it is possible to imagine an exponential decline in car use in cities that could lead to 50% less passenger kms driven in cars. The key mechanism is a quantitative leap in the quality of public transport whilst fuel prices continue to climb, accompanied by an associated change in land use patterns. This is due to a phenomenon called Transit Leverage whereby one pass km of transit use replaces between 3 and 7 pass kms in a car due to more direct travel (especially in trains), trip chaining (doing various other things like shopping or service visits associated with a commute), giving up one car in a household (a common occurrence that reduces many solo trips) and eventually changes in where people live as they prefer to live or work nearer transit.

Street Planning and Mobility Management


If cities build freeways then car dependence quickly follows. This is because the extra speed of freeways means that the city can quickly spread outwards into lower density land uses as the freeway rapidly becomes the preferred option. If on the other hand a city does not build freeways but prefers to emphasise transit it can enable its streets to become an important part of the sustainable transport system. Streets can be designed to favour pedestrians and cyclists and wherever this is done, cities invariably become surprised at how much more attractive and business-friendly it becomes – see the many projects and publications from Jan Gehl.

Sustainable mobility management is about “streets not roads”, whereby the streets are used for a multiplicity of purposes, not just maximising vehicle flow. The emphasis is on achieving efficiency by maximising people movement, not car movement and on achieving a high level of amenity and safety for all street users. This policy also picks up on the concept of integration of transport facilities as public space. One of the ways that US and European cities are approaching this is through what are called ‘Complete Streets’ or in the UK ‘Naked Streets’. This new movement aims to create streets where mobility is managed to favour public transport, walking and cycling in streets as well as traffic which is reduced in capacity somewhat, mainly through reduced speed. The policy often includes removing all large signs for drivers which means they automatically slow down; in Kensington High Road in London the traffic accident rate has halved.

Building freeways does not help either the brown agenda or the green agenda. It will not help a city save fuel as each lane rapidly fills leading to similar levels of congestion that were found before the road was built. Indeed studies have shown that there is little benefit for cities when they build freeways in terms of congestion and as that is the main reason for building them it does seem a waste. Data from Texas Transportation Institute show there is no overall correlation between delay per driver and the number of lanes of major roads built per head of population for the 20 biggest cities in the USA.

Thus for urban planners the choices for a more sustainable city are quite stark though politically they are much harder as the allure of building more road capacity remains very high. Many cities that have confronted the provision of a freeway have been global leaders in this move towards more sustainable transportation. In Copenhagen and Zurich, in Portland, Vancouver and Toronto, all had to face the cathartic experience of a controversial freeway. After a political confrontation the freeway options were dropped. They decided instead to provide other greener options and hence the building of light rail lines, cycleways, traffic calming and associated urban villages began to occur. All these cities had citizen groups that pushed visions for a different, less car-oriented city and a political process was worked through to achieve their innovations. Similar movements are active in Australia.

Freeways have blighted the centres of many cities and today there are cities that are trying to remove them. San Francisco removed the Embarcadero Freeway from its blighted waterfront district in the 1990’s after the Loma Prieta earthquake. It took three ballots before consensus was reached but the freeway has been rebuilt as a friendlier tree-lined boulevard involving pedestrian and cycle spaces. As in all cases where traffic capacity is reduced the city has not found it difficult to ensure adequate transport as most of the traffic just disappears. Regeneration of the land uses in the area has followed this change of transportation philosophy.

Seoul in Korea has removed a large freeway from its centre that had been built over a major river. The freeway had become controversial because of its blighting impacts on the built environment as well as the river. After a mayoral contest where the vision for a different kind of city was tested politically the newly elected mayor began a five year program that saw:

  • The freeway dismantled
  • The start of a rehabilitation process for the river
  • The restoration of an historical bridge over the river
  • Restoration and rehabilitation of the river foreshores as a public park
  • Restoration of adjacent buildings
  • Extension of the underground rail system to help replace the traffic

The project has been very symbolic for the city as the river was a spiritual source of life for the city. Now other car saturated Asian cities are planning to replace their central city freeways (

What these projects have shown is that we should as David Burwell from People for Public Spaces says ‘think of transportation as public space’. Freeways thus, from this perspective, become very unfriendly solutions as they are not good public spaces. However boulevards with space for cars, cyclists, pedestrians, a busway or LRT, all packaged in good design and with associated land uses that creates attractions for everyone – these are the gathering spaces that make green cities good cities. In the UK the Demos Institute has shown how public transport helps create good public spaces that help define a city. The change of awareness amongst traffic engineers of this new paradigm for transportation planning is gathering momentum. Andy Wiley-Schwartz says that ‘Road engineers are realising that they are in the community development business and not just in the facilities development business’. He calls this the ‘slow road ‘movement. In essence it means that urban planners are asserting their role over traffic engineers or at least making an integrated approach rather than one that reduces city function down to vehicle movement.

With this changed approach to city planning the small scale systems of pedestrian movement and cycling become much more important. Pedestrian strategies enable each centre in a city to be given priority to the most fundamental of human interactions, the walking-based face-to-face contact, that gives human life to a city and in the process reduces ecological footprint.

Cycle strategies can go across the city with greenways that improve the green agenda as well as lowering energy use. Enough demonstrations now exist to show that pedestrian strategies and bicycle strategies work dramatically to improve city economies and to help create a Resilient City. The work of Jan Gehl in Copenhagen followed by pedestrian strategies in all Australian cities, London, New York and San Francisco, the work of Enrique Penelosa in Bogota, the dramatic changes in Paris with the Velib bicycle scheme and the growing awareness that it works in developing cities as well, are all testament to this new approach to cities.