A literature review of the environmental effects and externalities of the transport sector and the concerns in sustainable transport planning is presented in this paper. The relation between air pollution and transport, considering that transport is an important air pollution emitter, is initially analyzed. The causal relationship between per capita GDP and individual consumption for transport, annual growth of global GDP and CO2 emissions and changes in CO2 emissions from fuel combustion by the various transport modes is then explained. Furthermore, energy consumption of transport modes for the EU countries is illustrated, as well as the relation between traffic flow and noise emissions and the implications of transport infrastructure to the landscape and environmental aesthetics. The increase in passenger mobility has caused traffic congestion, constituting an effect which is also quantified. Furthermore, the impact of accidents in terms of injuries, impairments and fatalities is a global social and public health issue. Moreover, the transport policies and the impact on economic and urban development, health, environmental protection and energy, focusing also on possible conflicts and convergence between safety and environmental policies are discussed. Finally, transport sector externalities, quantification in monetary units and possible effects of eventual internalization of these external costs are presented.