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Transport: Carbon Emissions

Volume 472: debated on Tuesday 4 March 2008

To ask the Secretary of State for Transport what estimate she has made of the carbon dioxide emissions per passenger mile from travel by (a) road, (b) air and (c) rail. (190548)

DEFRA's Company Reporting Guidelines published in 2007, available at

enable existing data sources, such as car mileage and fuel consumption, to be converted into illustrative carbon dioxide equivalent data. Using the guidelines to determine average carbon dioxide emissions per passenger km and converting to passenger mile produces the following results:

Carbon dioxide emissions per passenger mile: (kg)



Average petrol car


Average diesel car



Long haul flights


Short haul flights


Domestic flights



National rail


For road, the factors used in the guidelines are estimated average values for the UK car fleet, travelling on average trips in the UK, per vehicle mile. This has been divided by an average car occupancy rate of 1.6 passengers to derive the average emissions per passenger mile figure given in the table.

The rail estimate is for national rail and refers to an average emission factor for diesel and electric trains.

For aviation, the emission factor is an aggregate representation of the typical emissions from illustrative types of aircraft for the three types of air services. Actual emissions will vary significantly according to the type of aircraft in use, the load, cabin class, etc. An uplift of 9 per cent. has been applied to account for non-direct routes, circling and congestion. This is in line with the evidence from the Intergovernmental Panel on Climate Change (1999).

DEFRA are currently updating the conversion factors and revised figures are due to be published soon.