Achieving Low Carbon City Transport Systems: a Case Study Based on London

Achieving Low Carbon City Transport Systems: a Case Study Based on London


M Tight, H Watters, ITS, University of Leeds, UK; A Bristow, University of Loughborough, UK


This paper describes the use of National Travel Survey diary data and a carbon calculator to estimate carbon emissions from personal transport for London. The model is used to assess the effectiveness of policy levers to reduce carbon emissions.


Transport is currently responsible for around a quarter of the UK?s total anthropogenic CO2 emissions and this proportion is projected to increase. The transport sector will undoubtedly need to play a significant role in achieving carbon reductions if the Government is to meet its ambitious long term goal of a 60% reduction by 2050. This paper reports on a research project which aims to examine the effects of personal transport activity in a major city on emissions of carbon. One of the key challenges facing policy makers is how to translate national policy towards carbon reduction to a more local level, in particular how best can such policy be implemented at a city level in order to bring about real reductions. Urban areas are often both concentrations of climate vulnerability as well as major consumers of carbon, while the concentration of activity in such relatively small areas gives a high potential for the development of innovative solutions, perhaps more so than elsewhere. The focus of this study is on personal travel in London and it provides a unique insight into the role that cities play in generating carbon emissions from transport and the kinds of policy instruments which could be used to effectively promote change in the ways that households choose to use the transport options available to them.

The paper starts with a discussion of the issues involved in defining the scope of travel associated with London and how carbon emissions were allocated. The difficulties of allocation when considering a finite geographical area such as a city are considerable, in particular how to identify and allocate emissions from the large number of work, shopping and leisure trips into the city from outside and those which are made by people from within the city outside of the boundaries. Consideration is also given to the issue, crucial for cities such as London, of how best to include the emissions from the large number of tourist related trips made by those from outside of the city.

The key tool used in this research was a computer based carbon calculator developed to investigate household carbon emissions from their personal transport activity using travel diary information. In this research the calculator was adapted so that household travel diary information obtained from the UK National Travel Survey (NTS) could be used, giving access to large sample sizes, even where a sub-region of the country is considered. The use of diary data in this manner is novel and that collected through the NTS is highly detailed and sufficient to supply a good enough overview of transport activity to permit the modelling of carbon emissions. Building up a picture of carbon emissions from travel associated with London has been done in two key stages. Firstly, the emissions patterns of households living within the greater London area have been estimated from their travel data. This includes carbon emitted from travel wholly within the London area and also from travel to destinations outside of London. For the latter travel an estimate of the carbon emissions for only the element of travel within the London area has been made. In this stage the spatial disaggregation of the data means it has also been possible to explore differences in emissions characteristics between households living in inner and outer London. The second stage of analysis considered the emissions of carbon within the London area caused by travel from households who live outside of London, but who travel into the area. As before, only the element of travel within the London area is used to estimate carbon emissions.

Between them these two elements give an overall estimate, for the sample, of carbon emissions associated with personal travel occurring in London. The paper continues by examining the range of policy levers which could be used to reduce carbon emissions from transport associated with London and using the carbon calculator software models how effective they could be in terms of moving London towards a more sustainable transport system. Consideration is given to the effectiveness of both national and London based policy levers and also their relative effectiveness in promoting more sustainable travel amongst different groups of households. The paper concludes that the use of travel diary data in this way provides an insight into the travel patterns of Londoners and hence their susceptibility to policy levers to reduce their carbon emissions. The approach is readily transferable to other cities or regions.


Association for European Transport