Transport plays a fundamental role in post-industrial society, despite the benefits to human welfare that a well-developed transport network can provide, there is a growing awareness of the potential inconveniences that can be attributed to its considerable growth in recent years (Bielli et al., 1998).Transport facilitates access to jobs, education, markets, leisure and other services, and has a key role in the economy (WHO, 2000). Many argue that the transport sector places a burden on the environment that far exceeds its carrying capacity, and the risk exists that ecological sustainability is seriously endangered by economic development (Bielli et al., 1998).
Transport firs became a significant source of air pollution after the problems of sooty smog from coal combustion had largely been solved in western European and North American cities. Since then, emissions from road, air, rail and water transport have been partly responsible for acid deposition, stratospheric ozone depletion and climate change (Colvile et al., 2000). The impact of a transport system on the environment varies according to the different transport modes involved (Bielli et al., 1998). Most recently, road traffic exhaust emissions have been the cause of much concern about the effects of urban air quality on human health and troposphere ozone production (Colvile et al., 2000).However, Urban travel consumes significant energy use and is a major contributor to harmful emission (Copper et al., 2001).
Accordingly, Transport accounts for 26% of global CO2 emissions and is one of the few industrial sectors where emissions are still growing (Chapman, 2007).Transport sector emissions grew 1412 million tones (31%) worldwide between 1990 and 2003 (ECMT, 2007). Transport share of CO2 emissions is gradually increase in all region of the world; its share of world emissions increased from 22% in 1999 to 24% in 2003 (ECMT, 2007).
The impact of transport on the global climate is not limited to vehicle emissions as the production and distributions of fuel from oil, a ‘wells to wheels’ approach, produces significant amounts of greenhouse gas in itself (Weiss et al., 2000). Elevated concentrations of GHG cause increased atmospheric heat retention, this creates higher global temperatures or what is more commonly known as global warming which suspected to cause adverse environmental consequences including coastal zones flooding and desertification (El-Fadel et