Q. Is high-speed rail better in CO2 terms than the alternatives? Don’t higher speeds mean more energy consumption?

Yes, to both. High-speed rail does perform better than the alternatives. The Eddington Transport Study estimated that the potential carbon savings from a high speed line between London and Scotland might be 0.5 million tonnes per annum, which would be valued at £3.2 billion over 60 years.

A conventional speed rail service would not achieve this transfer. It’s worth the additional energy from high-speed (which adds about 30% to the energy cost) in order to take this market share from the environmentally inferior air sector (Eurostar produces one tenth of the carbon, per passenger journey, as does air). And it’s important not to forget that there is an important resource benefit from higher speeds: it means that the fleet requirement for a given capacity is reduced, compared with a lower speed option.

Q.Could high-speed rail make a difference to existing airport expansion plans?

Research by Greengauge21 in The Impact of High Speed Rail on Heathrow Airport shows that connecting Heathrow into the HS1 and the north-south network would encourage a passenger transfer from both domestic and short-haul European flights to surface transport. This could complement the role of the airport in the wider economy and enhance its effectiveness as a hub airport by freeing capacity for valuable long-haul flights.

Q. Wouldn’t carbon emissions be reduced even lower if we just restricted air use and didn’t bother with high-speed rail?

No. If you examine those charged with looking at the implications of climate change, such as the 2006 report, Living within a carbon budget, from the Tyndall Centre, you will see that, as a means of meeting carbon reduction targets, they advocate investment in capacity in faster rail services. Our response on climate change still needs to sustain a viable and vibrant economy for all of the obvious reasons, and now also because of the need to invest in more energy efficient ways of living.

Transport is a problem sector in carbon terms, and much of the policy response has to be to try to restrain demand. Rail, as generally the most benign mode, has to contribute proportionately more, within this demand management framework. Careful design from the outset, such as has been employed in Japan, which has ensured that energy costs/passenger have not increased as high-speed trains have got progressively faster (from 200km/h to 360km/h), should help minimise carbon emissions.

Q. How can a high-speed rail network, as opposed to conventional-speed, electrically-powered rail, be described as ‘environmentally benign’?

Because we have a rapidly expanding domestic air market that would be cut back in response to passengers switching to rail. But there is a wider and very important reason why high-speed rail is the most sustainable of transport investments.

Nearly all transport projects have the effect of encouraging a more dispersed pattern of land use development. Even urban transit schemes such as light rail, while benefiting the city centre generally, also stimulate demand and development on the urban periphery. Nearly all major road schemes have this effect of encouraging new buildings (business parks, retail centres, logistics centres, leisure centres, etc) in edge-city locations and on previously undeveloped land. Yet, crucial to achieving a reduced carbon footprint are the reinvigoration of cities and the creation of lifestyles that are not car dependent.

High speed rail uniquely will stimulate development in city centres, helping the process of renaissance that has already started in some cities. In so doing, high-speed rail can reduce pressures to develop in the countryside. It is because of this intrinsic relationship with cities and their development, that high-speed rail can be rightly seen as environmentally most benign, a means of taking pressure off sensitive and overheated parts of the country, fully congruent with sustainability objectives.