This chapter assesses what is known about measures already being taken or that might be taken to improve the fuel efficiency of aviation through changes in aircraft operations and changes in the way air traffic is managed against a background of continuing growth in air transport activity. The objective of such improvement in fuel efficiency is to reduce the amount of fuel consumed for a given demand for air transportation-which would have the effect of reducing emissions.
The existing air navigation system and its subsystems suffer from technical, operational, political, procedural, economic, social, and implementation shortcomings. The International Civil Aviation Organization (ICAO), national airworthiness authorities, regional bodies, and private-sector stakeholders have identified the need for radical improvement of the air traffic management system to accommodate the continuing growth of aviation and to promote efficient airspace use. Implementation of a new concept for air traffic management that includes enhanced communications, navigation, and surveillance in support of an improved air traffic management system has already begun. Communications, navigation, and surveillance/air traffic management (CNS/ATM) systems benefit the air transportation sector by reducing delays, increasing the capacity of existing infrastructure, and improving operational efficiency. This system results in fuel savings, hence reduced emissions for a given demand.
Several studies associated with the implementation of CNS/ ATM systems have been carried out. Although some of these studies provide results in terms of cost/benefit and associated fuel savings and do not specifically address environmental benefits, there is an obvious correlation with reductions in gaseous emissions. These studies suggest that improvements in air traffic management could help to improve overall fuel efficiency by 6-12%.
Other strategies that exist for mitigating the environmental impact of emissions from aviation could achieve environmental benefits through reduced fuel burn. These strategies include: optimizing aircraft speed, reducing additional weight, increasing the load factor, reducing nonessential fuel on board, limiting the use of auxiliary power units, and reducing taxiing. Airlines are already under strong pressure to optimize these parameters, largely because of economic considerations and requirement within the industry to minimize operational costs. The potential reduction in fuel burn by further optimization of these operational measures is in the range of 2-6%.
To answer the question of whether emissions reductions could be achieved by substituting the use of air transport by other modes, several studies have compared fuel burn and carbon dioxide emissions from different modes of transport. The amount of carbon dioxide emitted per passenger-km for the different modes of transport is very dependent on the distance travelled; the type of aircraft, train, or car; the load factor; and the source of energy used. Substitution of rail and coach for air travel could result in the reduction of emissions per passenger-km. However, the potential reduction would be achieved only for passengers travelling relatively short distances and only on high-density routes that have rail or coach links. Finally, substituting other transport modes for air transport could have environmental impacts on, for example, local air quality and noise exposure (which are outside the scope of this report).
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