Investment in HSR is expensive. The key benefits are typically time savings for business and leisure travel, more comfortable journeys with the ability to use the time spent travelling and increased rail capacity. Most successful applications of high speed rail seem to arise when there is both a need for more rail capacity and a commercial need for higher speeds. It seems difficult to justify building a new line solely for purposes of increased speed unless traffic volumes are very large, but when a new line is to be built, the marginal cost of higher speed may be justified; conversely the benefits of higher speed may help to make the case for more capacity. It follows from the above that appraisal of HSR will need to include assessment of the released capacity benefits for freight, local and regional passenger services and the changes in service levels on the conventional lines. It also follows that the case for HSR is often heavily dependent both on future economic growth and on the assumption that demand for long distance passenger and freight transport will continue to increase. If long run economic recession, or environmental constraints prevent this from occurring then far less new HSR will be justified than in a „business as usual‟ scenario. Already the current recession will have at least delayed the case for some new lines, although increased government spending to reflate the economy may have the opposite effect.
It is important to consider network effects. The benefits of a high speed line may be maximised by locating it where it may carry traffic to a wide number of destinations using existing tracks beyond the end of the high speed line, whilst extensions to an existing network lead to greater benefits than isolated new lines by attracting increased traffic to the network as a whole. Obviously this implies technical compatibility between HSR and existing rail as a prime requirement.
High speed rail is more successful at competing with air than car, and there is evidence for the widely quoted 3 hour rail journey time threshold (although this evidence predates the increased security and congestion at airports which is believed to have increased this threshold). Where rail journey times can be brought close to or below 3 hours HSR can be expected to take a major share of origin-destination aviation markets.
Of the measured external benefits of HSR investment, reduced congestion is the most significant. Relief of road congestion is, however, unlikely to be a major part of the case for high speed rail except where chronic congestion is spread throughout the day along much of the route. Relief of airport capacity through transfer of domestic legs from air to rail is potentially more important where capacity is scarce and expansion is difficult, costly and has a serious environmental impact, as in the case of Heathrow. However, according to the HS2 study, even if HS2 served Heathrow directly, the number of slots released by diversion of domestic traffic from air to rail would be relatively small (HS2 Ltd, 2009).
Environmental benefits are unlikely to be a significant part of the case for high speed rail when all relevant factors are considered, but nor are they a strong argument against it provided that high load factors can be achieved and the infrastructure itself can be accommodated without excessive environmental damage. Regarding global warming, key factors are the extent to which the scheme diverts traffic from air, as opposed to conventional rail, and the source of primary energy used to generate the electricity.
The issue of wider economic benefits remains one of the hardest to tackle; such benefits could be significant, particularly if the route is heavily used for commuting, but vary significantly from case to case, so an in depth study of each case is required.
The breakeven volume of passengers to justify a new high speed line is very variable, ranging from 3m to 17m in the first year of operation under possible assumptions examined, but typically even under favourable conditions at least 9m passengers per annum will be needed. Whilst it appears that all the French high speed lines comfortably exceeded this volume, it is clear that some proposals are being developed where traffic is very much less dense (the Madrid-Seville line, for instance, is still only at around the 5m level). The most important variable in determining the breakeven volume is the construction cost, which varies enormously according to circumstances.
Photo Credit: jamesjustin
