Tuesday, June 8, 2010

Debate: "Does high density development make travel more sustainable?"

Two experts on transport planning, Peter Headicar and Marcial Echenique, tell us what they think about the role of spatial planning in encouraging more sustainable travel. 

Peter Headicar and Marcial Echenique.
Peter Headicar and Marcial Echenique. 

Our experts tackled two questions. Can land use planning make travel more sustainable and does high density, mixed use development encourage sustainable travel? This is the first debate that we have hosted on Sustainable Cities - read the views of Marcial and Peter, make up your mind and have your say.

Peter Headicar is reader in transport planning at Oxford Brookes University and Marcial Echenique is head of architecture and professor of land use and transport studies at the University of Cambridge. This article summarises the discussion at a debate which took place in January 2010.

Can land use planning help make travel more sustainable?

Planning for sustainable travel

CO2  emissions from household cars by trip length and journey purpose (GB 2002-2006 average). Medium-distance journeys are responsible for the greatest proportion of CO2 emissions (click to see a bigger image).

Yes - Peter Headicar

Land use can have a major effect on how and why people travel. The location of your home in relation to your office, the shops or your children’s school has a direct influence on the choices you have about what mode of transport you use and how far you travel. For example, when the shops are just around the corner, you can chose to walk rather than taking the car. So it should be possible to use land use planning to encourage more sustainable travel.

Unfortunately, in the UK the influence of land use planning on reducing car use is limited by weak transport policies. Too often driving is the cheapest and easiest option. People often feel that streets are unsafe for walking or cycling, train fares are too expensive and bus services are slow and inconvenient. Transport policies have been improving but will need to change a lot more in future to cope with worsening congestion, climate change and higher oil prices.

In addition most spatial planning is focused at the local level which makes it difficult to have a big impact on car use. The focus on urban form within settlements and using site travel plans to reduce driving ignores questions about the relationship of different types of land use to their wider contexts. What really matters is the strategic location of development and the balance of jobs, houses and other land uses within and between whole towns and cities at the sub-regional level. It’s the longer journeys between towns, of between 5 and 25 miles, that are responsible for a much greater proportion of overall car mileage and hence CO2 emissions.
Although the effects of spatial planning on travel may be limited at the moment, that doesn’t mean we should relinquish the current and future benefits which it does offer. Land use patterns change very slowly. Our decisions now will have an influence for decades or even centuries to come. Working on the precautionary principle, we should continue to foster a pattern of land use that will support more sustainable travel in the future. By contrast lower density, more dispersed patterns will make sustainable transport policies impossible to implement.

To raise awareness of the links between spatial planning and travel, emphasising the strategic dimension, the Commission for Integrated Transport has recently published a web-based guide, www.plan4sustainabletravel.org. The website helps local planning authorities identify and promote the right type of development in the right location to reduce the need to travel and reduce car mileage.
The ReVISIONS programme – designing cities of the future. Land use planning should be used to determine what sustainable infrastructure and technologies are practical where, but not to try and influence travel patterns.

No - Marcial Echenique

Land use planning has very little effect on how people travel – what really matters are cost and convenience.
Current land use and transport policies try to improve environmental sustainability by reducing the need to travel (e.g. by promoting compact cities and mixed use, high density development) and persuading people to walk, cycle or use public transport. However, in reality socio-economic trends such as rising incomes and a shift from manufacturing to service industries have a much greater effect on travel patterns.
To make travel more environmentally sustainable, we should focus instead on technological improvements. Efficiency in cars is improving rapidly and further gains can be achieved with the introduction of hybrids and electrical cars. Spatial planning is important to determine which technologies are practical where. For example, combined heat and power is better for compact urban areas whereas solar power or ground source heat pumps work better at lower densities. This is the direction our research (the ReVISIONS programme, Regional Visions of Integrated Sustainable Infrastructure Optimised for Neighbourhoods) is heading.

Does higher density urban development encourage more sustainable travel?

Population density and annual distance travelled (NTS, 2002-06). At higher densities people don’t drive so far but travel further by bus and train (click to see a bigger version).

Yes - Peter Headicar

We should use spatial planning to make travel more environmentally sustainable by concentrating growth in and around major urban settlements with higher density development. People who live in towns and cities don’t have so far to travel between their homes, schools, jobs and shops. They have more choice about what mode of transport they want to use. For example, they can choose to use public transport that is nearby or to walk between places that are close together.

Data on travel patterns in the UK provides clear evidence of the links between density, accessibility and travel. At higher densities (especially over 30 people per hectare) the average annual distance travelled per person falls, particularly distance travelled by car. The distance travelled by public transport increases. Areas with very good levels of accessibility to public transport have lower levels of car use and higher proportions of public transport, walking and cycling.
Alternative patterns for future urban growth. Market led dispersal gives people more living space and increases economic competitiveness.

No - Marcial Echenique

The received wisdom is that high density, mixed use developments using brownfield sites are more environmentally sustainable because they reduce people’s need to travel. But this is simply not the case. Recent evidence shows that in developed countries doubling the population density only reduces the distance travelled by car per person by 5 to 10%. This conclusion from SOLUTIONS research (www.suburbansolutions.ac.uk) has been confirmed in a comprehensive study by the US Academy of Science.
Concentrating growth in urban centres damages economic growth and quality of life. High density cities are overcrowded and expensive. Because there is more travel by car in the same space (as there is double the population) there is more congestion, more energy use and more CO2 emissions. Because travel takes longer it costs more. People travel shorter distances and the economy suffers.

By contrast, in lower density places where travel is easy, people have better access to a wider selection of jobs, homes, shops and services. Businesses have a larger market area for their goods – there’s more competition, lower prices and greater prosperity.

If we want to build successful, prosperous places, we have to let people live where they want. We should stop forcing people into flats built on brownfield land – in places where people don’t actually want to live and where there is little economic growth. Take development the south of England for example – employment is growing in the west and south whereas new homes are being built to the east in places such as the Thames Gateway. Instead, we should promote low density, dispersed development where there is a quick, efficient flow of goods and people.