The demand for improvement and expansion in the transport infrastructure is a derived demand which generally reflects the level of economic activity of a country. Current transport trends for OECD countries indicate that both freight and passenger traffic are likely to grow steadily as has been the case during the last few decades. According to a recent estimate, the annual worldwide increase in the vehicular fleet has averaged 10 million cars and 5 million buses and trucks. If the trend continues, a billion vehicles will use the world's roads by 2030 (Walsh, 1990). Similarly, the railway passenger and freight transport has also increased substantially. The former USSR and the eastern Europe have dominated railway freight accounting for more than 50% of the total world's rail freight (Tolba, 1992).

The adequacy of ports in terms of depth, ease of entry and standards of facilities pose certain constraints for effective development of transportation by ship. Until the last decade, there have been 2,448 ports in the world of which 1059 were in developing countries (Llyods, 1987; Tolba, 1992).

Transport by air is growing very rapidly in all parts of the world and along with it there is an unprecedented progress in expansion and construction of airports (Meyers, 1988). Between 1972 and 1990, the number of passenger - kilometer of air travel has more than tripled. The freight has increased from 5940 million tons in 1978 to 53450 million tons in 1988 (Tolba, 1992) and this trend is expected to continue. Therefore, it seems likely that air transportation will eventually surpass railways as a mass passenger carrier and the congestion problems in the air corridors will become a major problem. The demand for fast and reliable distribution of goods, increasing pace of containerization, increasing value of transported goods and fast emerging need for `just in time' services will continue to increase the reliance on air transportation. The manifold environmental problems associated with transport infrastructure often counter the economic benefits derived from them (Table 1).

Table 1. Selected environmental effects of principal transport modes.

• Air Transportation And Environmental Concerns
   
• Threats To Wildlife Conservation Associated With The Air Transportation
   
• Proposal For Airport Project In Mizorum
   
• Background Of The Proposed Airport Project
   
• Project Profile
   
• Environmental Impact Assessment Studies Of The Proposed Project
   
• Scope Of Work