IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group III: Mitigation of Climate Change Land use and transport planning

Energy use for urban transport is determined by a number of factors, including the location of employment and residential locations. In recent decades, most cities have been increasing their dependence on the automobile and decreasing dependence on public transport. In some cases increasing motorization is the result of deliberate planning – what became known as ‘predict and provide’ (The Royal Commission on Transport and the Environment, 1994; Goodwin, 1999). This planning and programming process played a central role in developed countries during the second half of the 20th century. In many developing countries, the process of motorization and road building is less organized, but is generally following the same motorization path, often at an accelerated rate.

Income plays a central role in explaining motorization. But cities of similar wealth often have very different rates of motorizsation. Mode shares vary dramatically across cities, even within single countries. The share of trips by walking, cycling and public transport is 50% or higher in most Asian, African and Latin American cities, and even in Japan and Western Europe (Figure 5.17). Coordination of land use and transport planning is key to maintaining these high mode shares.

Kenworthy and Laube (1999) pointed out that high urban densities are associated with lower levels of car ownership and car use and higher levels of transit use. These densities are decreasing almost everywhere. Perhaps the most important strategy and highest priority to slow motorization is to strengthen local institutions, particularly in urban areas (Sperling and Salon, 2002).

Figure 5.17

Figure 5.17: Modal split for the cities represented in the Millennium Cities Database for Sustainable Transport by region

Source: Kenworthy & Laube, 2002.

Some Asian cities with strong governments, especially Hong Kong, Singapore and Shanghai are actively and effectively pursuing strategies to slow motorization by providing high quality public transport and coordinating land use and transport planning (Cullinane, 2002; Willoughby, 2001; Cameron et al., 2004; Sperling and Salon, 2002).

There are many other examples of successfully integrated land use and transport planning, including Stockholm and Portland, Oregon (USA) (Abbott, 2002; Lundqvist, 2003). They mostly couple mixed-use and compact land use development with better public transport access to minimize auto dependence. The effectiveness of these initiatives in reducing sprawl is the subject of debate, especially in the USA (Song and Knaap, 2004; Gordon and Richardson, 1997; Ewing, 1997). There are several arguments that the settlement pattern is largely determined, so changes in land use are marginal, or that travel behaviour may be more susceptible to policy interventions than land-use preferences (Richardson and Bae, 2004). Ewing and Cervero (2001) found that typical elasticity of vehicle-km travelled with respect to local density is –0.05, while Pickrell (1999) noted that reduction in auto use become significant only at densities of 4000 people or more per square kilometre – densities rarely observed in US suburbs, but often reached elsewhere (Newman and Kenworthy, 1999). Coordinated transport and land-use methods might have greater benefits in the developing world where dense mixed land use prevails and car ownership rate is low. Curitiba is a prime example of coordinated citywide transport and land-use planning (Gilat and Sussman, 2003; Cervero, 1998).

The effectiveness of policies in shifting passengers from cars to buses and rails is uncertain. The literature on elasticity with respect to other prices (cross price elasticity) is not abundant and likely to vary according to the context (Hensher, 2001). The Transport Research Laboratory guide showed several cross price elasticity estimates with considerable variance in preceding studies (TRL, 2004). Goodwin (1992) gave an average cross elasticity of public transport demand with respect to petrol prices of +0.34. Jong and Gunn (2001) also gave an average cross elasticity of public transport trips with respect to fuel price and car time of +0.33 and +0.27 in the short term and +0.07 and +0.15 in the long term.

The literature on mode shifts from cars to new rail services is also limited. A monitoring study of Manchester indicated that about 11% of the passengers on the new light rail would have otherwise used their cars for their trips (Mackett and Edwards, 1998), while a Japanese study of four domestic rails and monorails showed that 10–30% of passengers on these modes were diverted from car mode. The majority of the passengers were transferred from alternative bus and rail routes (Japanese Ministry of Land, Infrastructure and Transport and Institute of Highway Economics, 2004). The Transport Research Laboratory guide (2004) contained international evidence of diversion rates from car to new urban rail ranging from 5–30%. These diversion rates are partly related to car mode share, in the sense that car share is so high in the USA and Australia that ridership on new rail systems is more likely to come from cars in those countries (Booz Allen & Hamilton 1999, cited in Transport Research Laboratory, 2004). It is also known that patronage of metros for cities in the developing world has been drawn almost exclusively from existing public transport users or through generation effects (Fouracre et al., 2003).

The literature suggests that in general, single policies or initiatives tend to have a rather modest effect on the motorization process. The key to restraining motorization is to cluster a number of initiatives and policies, including improved transit service, improved facilities for NMT (Non-motorized transport) and market and regulatory instruments to restrain car ownership and use (Sperling and Salon, 2002). Various pricing and regulatory instruments are addressed below.

Investment appraisal is an important issue in transport planning and policy. The most widely applied appraisal technique in transport is cost benefit analysis (CBA) (Nijkamp et al., 2003). In CBA, the cost of CO2 emissions can be indirectly included in the vehicle operating cost or directly counted at an estimated price, but some form of robustness testing is useful in the latter case. Alternatively, the amount of CO2 emissions is listed on an appraisal summary table of Multi-Criteria Analysis (MCA) as a part of non-monetized benefits and costs (Mackie and Nellthorp, 2001; Grant-Muller et al., 2001; Forkenbrock and Weisbrod, 2001; Japanese Study Group on Road Investment Evaluation, 2000). To the extent that the cost of CO2 emissions has a relatively important weight in these assessments, investments in unnecessarily carbon-intensive projects might be avoided. Strategic CBA can further make transport planning and policy carbon-efficient by extending CBA to cover multi-modal investment alternatives, while Strategic Environmental Assessment (SEA) can accomplish it by including multi-sector elements. (ECMT, 2000; ECMT, 2004b).