A Report on the Research Methods of UK Transport

Published 27 Feb 2017

1.1 Purpose
The purpose of this report is to critically assess and analyse the approach and methodology in determining the comparative environmental burdens of high-speed rail and short haul air travel for regional domestic journeys.

1.2 Scope
This report compares the two modes of transport for specific journeys between the main domestic flight routes in the UK, namely between London and: Manchester, Leeds, Newcastle, Edinburgh and Glasgow.

1.3 Data, sources, and methods applied

An assessment of current environmental burdens for each route, per passenger carried, based on average load factors-33% average seat occupancy for rail routes, and typically 65 – 75% for air routes. The future changes in these environmental burdens were also considered. This is because there will be a planned upgrade and fleet changes in future years.
“Greenhouse” gas emissions were measured to determine CO2 emissions, per passenger in kilometers (Km). Other atmospheric emissions to determine the SO2, NOx, CO, PM10 content were considered. Emissions from surface access were investigated. The noise level and its burden to the environment and also the determination of “Land-take” and its impact to the environment such as habitat loss, fragmentation and community severances were considered also as a yard stick for carrying out this report.

1.4 Limitations
Certain limitations were encountered in this report. Future changes in average load factors have not been considered. This is because it is beyond the scope of this study and lack of relevant data.


2.1 Greenhouse Gas Emissions
It can be argued that short-haul air journeys have lighter CO2 emissions, per passenger (Km), than high-speed rail. Domestic aircraft have emission of 200 – 300gCO2/passenger km compared to around 40g CO2/passenger km for high–speed rail.

Atmospheric Pollutants (SO2, Nox, Co, Pm10 And VOC5)
High–speed rail journeys have a higher SO2 emission, per passenger (km), than domestic air. This is due to the fact that there is a high SO2 emission from the UK electricity generating mix – coal fired generation. The SO2 emission from high-speed trains is projected to fall significantly in future years.

Domestic aircraft have higher emissions of ground level CO, NOx and VOCs, per passenger (km), than high-speed rail and are higher on shorter trips, because of emissions from take – off and landing. The only exception to this, was the analysis of high-speed diesel trains in the London-Edinburgh route. These diesel trains have a higher emission but will be passed out in the next few years. Future emissions of CO, NOx and VOCs will be lower for high-speed electric trains due to changes in electricity generation mix.

Emissions of PM10, per passenger km are broadly similar for both modes of transportation. Emissions of PM10 for both modes will reduce significantly in future years (2006 and beyond) due to reductions in the emissions from the electricity generation mix for rail and from modern aircraft.

Emission from surface access may also be important but for lack of data, it is not possible to access surface emissions for high-speed rail and domestic aircraft, though surface emissions are likely to favour rail over air.


The noise burden for both modes of transportation and for both existing and additional journeys is extremely site and route specific but aircraft in use on domestic routes may have a small advantage in terms of absolute noise burden but this does not mean that it has a higher noise impact. Background noise levels determine the relative burden of a regional journey. On route by route basis, therefore, it is not possible to ascertain that one mode of transportation has a lower noise burden than the other.


“Land-take” have a number of potential environmental impacts but it is not possible to compare the relative “Land-take” for both modes of transportation.


Unlike plane and cars, high-speed rail avoids the pollution externally because the electricity that powers the train is considered the “transportation sector.”

In comparing the effect on the environment of high-speed rail and short-haul air travel for regional domestic journeys, we conclude that high-speed rail has a lower external pollution than short-haul air travel.

High-speed rail therefore has a comparative advantage on the environment with regards to environmental pollution than short-haul air travel.


  • ATAG, (2006),
  • Bass, Frank M. (1969), “The Effect of Air Transport and High-Speed Rail on Environment,” Boston: Mcgrawhill Press, January 1975.
  • Levinson, David (2006), “The Full Cost of Intercity Travel”, A Comparison of Air, Highway and High Speed Rail. Chicago Press, February 2006.
  • Watkiss, R. Jones, D. Rhodes, A Hardy, C. Handley, C. Walker, Published July 2001.
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