Some of the most promising opportunities for GHG mitigation in the transport sector are linked to the growing need for action to address a wider range of concerns about the sectors social and environmental impacts. Several studies have evaluated environmental and social externalities associated with road transport (IPCC, 1996; ECMT, 1997; OECD, 1997a). Some have explored the effects of internalizing those costs through fuel taxes and other measures (EC, 1996; Michaelis, 1996b; ECMT, 1997). However, transport fuel taxes have proved very unpopular in some countries, especially where they are seen as revenue-raising measures (MVA, 1995), and may be an inefficient means of internalizing environmental costs other than those associated with carbon dioxide (CO2) emissions. Charges on road users, including parking fees in many towns and tolls, especially on motorways, have been accepted where they are earmarked to cover the costs of road provision (Michaelis, 1997a). Several studies have explored the potential for adjusting the way existing road taxes, license fees, and insurance premiums are levied, and have found potential emissions reductions in the region of 10% in OECD countries (Wenzel, 1995; Michaelis, 1996b).
While it may be possible to adjust the price incentives in the transport sector, overcoming the many forms of inertia and lock-in is more difficult. Effective mitigation strategies would entail combinations of measures, just as the status quo is currently maintained by a combination of forces (IPCC, 1996). Often, the best opportunities for such concerted action arise at a local level, where the negative impacts of transport are most keenly felt (Michaelis, 1997a). There are several positive experiences of change, such as a Scottish example where a public consultation process led to a large shift in local government spending towards public transport (Macaulay et al., 1993), initiatives to introduce toll rings around Norwegian cities, and the comprehensive transport strategies in Singapore (Ang, 1993), Curitiba (Rabinovitch, 1993), and other cities (IPCC, 1996).
Achieving the promise of new technology may depend on international co-operation to develop larger markets for low-GHG-emission vehicles through fiscal and regulatory measures and public purchasing. During high oil price periods, car importing countries have imposed restrictions and incentives on car importers to discourage the use of more energy-intensive cars. Agricultural surpluses and foreign exchange shortages have been important stimuli for technology development in the past, in particular in the case of the Brazilian ethanol programme.
While several studies have found that people living in denser and more compact cities rely less on cars (Armstrong, 1993), energy savings alone are unlikely to motivate the shift away from suburban sprawl to compact cities advocated by Newman and Kenworthy (1990). However, there is a growing concern to reverse the decline in the environment and in communities in city centres by moving away from zoning and car-based transport, and towards multi-function, high-density pedestrian zones. There is a considerable opportunity for GHG mitigation in linking to this concern. In particular, there is scope where infrastructure is developing rapidly to implement planning measures that encourage more sustainable transport patterns, avoiding the pollution, congestion, higher accident rates, and GHG emissions associated with cars.
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