The potential of the railway to reduce greenhouse gas emissions

摘要

Concerns about Climate Change have led to a need to reduceGreenhouse Gas (GHG) emissions significantly, and the transportsector is not excluded from this. To meet emissions reductiontargets it is likely that consideration will need to be givento changing individual travel behaviour, which may includeencouraging modal shift towards modes with a lower environmentalimpact.Carbon dioxide (CO_2) forms the bulk of GHG emissionsfrom the transport sector. Operationally, electric trains typicallyproduce less CO_2 per passenger km travelled than cars orshort-haul aeroplanes. In theory, therefore, the railway can offera relatively high level of environmental performance, makingit a good target for modal shift.However, it is important to take a holistic view and notethat emissions from a transport system stem from more thanthe movement of passengers or freight between two points.Emissions from the construction and maintenance of bothvehicles and infrastructure are potentially significant andanalysis of the whole life-cycle should be undertaken.Sources of electricity generation are a key variable whendetermining the emissions from electric trains. Additionally,the load factors attained by the different modes of transporthave a big effect on the environmental impact per passenger.It is also important to challenge the assumption that a shift inpassengers from road or air to rail will automatically lead to areduction in car journeys or flights.A simple illustrative model is used to demonstrate the possibilityof a net reduction in emissions if a new railway is builtand modal shift from road and air occurs. Building on a basicconsideration of operational emissions the model is expandedto include wider life-cycle impacts and it is shown that the railwaymay retain an environmental advantage. The illustrativemodel is then used to examine the possible effects of some ofthe other influencing factors.Reference is made to ways of maximising the potential benefits,and a discussion is included on how to encourage modalshift of passengers from road and air. Very brief reference isalso made to freight transport (for which the railway also has apotential advantage over road transport).