Climate Change Information Sheet 26
New transportation technologies and policies
- The transport sector is a major and rapidly growing source of greenhouse gas emissions. Fossil-fuel combustion in vehicles and transport equipment accounted for about one-fifth of global carbon dioxide emissions in 1990. Transportation's global fuel consumption rose by 50% between 1973 and 1990, largely because of higher incomes and steady or declining fuel costs. Without new measures to slow the growth in emissions, the use of fossil fuel for transportation is expected to increase by another 35130% by the year 2025. Transportation also contributes to local and regional pollution problems through its emissions of carbon monoxide, lead, sulfur oxides (SOx) and nitrogen oxides (NOx).
- Automobiles are the transport sector's largest consumer of petroleum and its largest source of carbon dioxide emissions. The developed world has the highest per-capita ownership of private cars today; developing countries currently claim a mere 10% of the world's cars, but are expected to account for most of the future growth in automobile use.
- New technologies can increase the efficiency of automobiles and reduce emissions per kilometer traveled. New materials and designs can reduce a vehicle's mass and increase the efficiency at which it converts energy, thus lowering the amount of energy required to move it. With improved transmission designs, engines can operate closer to their optimal speed and load conditions. Technological improvements in combustion-engine technology and in petroleum formulations have already started to reduce per-vehicle emissions of both greenhouse gases and conventional pollutants. The energy intensity of these engines can probably still be improved by 1530% using current technology. More dramatic improvements could be achieved by, for example, adopting hybrid cars that use a combination of fuel-fired engines and electric motors.
- Switching to less carbon-intensive fuels can also reduce carbon dioxide emissions. The feasibility of operating vehicles on fuels other than gasoline has been demonstrated in many countries. Alternative transport fuels include compressed natural gas, ethanol, methanol, and electricity derived from non-fossil sources. Compressed natural gas has been used successfully in fleet vehicles for a number of years in the US, Europe, and New Zealand. Brazil has a programme to promote the use of cars fueled by ethanol derived from sugar cane and other biomass. Such programmes can offer long-term global climate benefits in tandem with immediate improvements in local air quality.
- Renewable energy technologies are becoming more and more competitive. Renewable energy could one day offer cost-effective alternatives to petroleum-based fuels. Electricity derived from hydroelectric, solar photovoltaics, wind systems, and hydrogen fuel cells can power the movement of people and goods with almost zero greenhouse gas emissions. The combustion of liquid fuels derived from sustainably grown biomass does emit carbon, but an equal amount of carbon is recaptured by the vegetation grown to make new biomass. The use of renewable fuels in the transport sector can help to reduce new CO2 emissions while delivering the degree of personal mobility that people desire.
- Emissions can be further cut through changes in maintenance and operating practices. Many vehicles are not adequately maintained due to high costs or to the limited local availability of spare parts. In some areas, maintenance may simply be a low priority for drivers and vehicle owners. Recent studies suggest that an average vehicle's fuel consumption can be reduced by as much as 210% just through regular engine tune-ups.
- Policies to reduce road traffic congestion can save both emissions and costs. The energy intensity of transport and the amount of congestion on the roads are strongly influenced by the average occupancy rate for passenger vehicles. Computerized routing systems for trucks can save money and fuel by optimizing payloads and minimizing time spent in traffic; some studies indicate that it is already technically possible to reduce energy use per tonne-kilometer by 2530%. Similarly, measures to improve general traffic control and restrict the use of motor vehicles have reduced energy use in some areas by as much as 2040%.
- Urban planners can encourage low-emissions transport. Convincing people to switch from automobiles to buses or trains can reduce primary energy use per passenger-seat-kilometer by 3070%. A vital part of encouraging this transition is providing safe and efficient public transport systems. Cities can also promote walking, bicycling, and car pooling by limiting automobile access to certain roads, increasing the fees for public parking, and converting existing roads into bicycle lanes, bus-access roads, or "High Occupancy Vehicle" (HOV) lanes during peak hours. The introduction of computerized traffic-light control systems, more informative signs, and improved network designs, especially in urban areas with a high density of vehicles during peak travel hours, can also boost efficiency. In the short term, the greatest potential that urban planning has for affecting transport is in rapidly developing cities where cars are still in limited use.
- Policies to reduce air traffic congestion can cut emissions while improving safety. Present flight patterns seek to reduce fuel consumption and other in-flight costs. Nevertheless, crowding at airports leads to long holding times at many destinations and contributes to higher-than-necessary fuel emissions. Advances in booking systems, policies to increase seat occupancy rates, and efforts to discourage simultaneous, partly-filled flights on the same route could further reduce congestion, minimize landing delays, and decrease emissions. Additional aviation fuel taxes could also play a role in promoting energy efficiency.
- Policies to accelerate the rate of capital stock turnover in automobile and aircraft fleets may be the quickest way to reduce the short-term rate of emissions growth. This is especially true for developed countries, where large fleets with many older vehicles are already in place. Rewards can be offered for retiring older vehicles and airplanes that do not meet current national emissions standards, or small environmental "user fees" can be imposed, with the fees proportional to the vehicle's energy consumption. Fuel-efficiency standards for autos and aircraft are vital to reducing the energy intensity of transport over the longer term, but they affect only the newest vehicles.
- The appropriate mix of policies will vary from city to city and country to country. In addition, measures to reduce emissions in the transport sector can take years or even decades to show their full results. But if carried out with care, climate-friendly transport policies can play a major role in promoting economic development while minimizing the local costs of traffic congestion, road accidents, and air pollution.
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