Public transport offers alternative modes of transport to the private motor car. Public transport, including trains, trams and buses, can relieve traffic congestion and reduce air pollution from road transport. The use of public transport must be encouraged if a sustainable transport policy is to be developed.
Railways are efficient forms of transport that use existing tracks, and therefore use less land than roads. One commuter train may hold hundreds of passengers which may otherwise have travelled to work by car. Although trains can reduce road congestion, it is important to remember that they still contribute to air pollution both directly and indirectly. Diesel engines produce a large amount of particulates. Electric trains do not release air pollutants directly, but their electricity produced "upstream" by power stations can contribute to acid rain and global warming if they use fossil fuels.
Buses are generally recognised as an environmentally friendly form of transport, particularly in relation to the number of car journeys needed to carry the same number of passengers. A bus uses less fuel per person carried, and hence less fuel than the number of cars needed to replace it. However, buses do contribute to air quality problems, particularly in cities. Buses in the UK are mainly powered by diesel engines, with a handful of alternative fuels under trial. Improvements in the emission performance of buses are likely to be needed in the future.
There has been a resurgence in the use of transport such as trams and light railway, which have a lower environmental impact than buses. Trams use smaller vehicles and tighter rail tracks than conventional trains, which enables them to be constructed within existing built-up areas. They also run at a lower cost than trains, and they can easily be expanded to accommodate increases in passengers.
An example of a successful light rail transport scheme is the Metrolink, developed in Manchester in 1991. Sections of the Metrolink run parallel to other vehicles in the existing road network. Since its successful instalment, additional extensions have been developed or planned to surrounding suburbs.
Public transport should form part of a wider integrated sustainable transport strategy. However, the cost and convenience of use of public transport needs to be lowered to encourage people to use this as an alternative to personal vehicles.