Introduction
The Chiltern Main Line has enjoyed something of a revival. It was hit hard by the Beeching Cuts, but new stations and track have been constructed/reinstated since the late '80s. Since Chiltern Railways took over after privatisation in the '90s, both it and the government have invested heavily in mainly the long distance aspect of their operations (London to Birmingham and latterly Oxford) meaning that the route now competes with the West Coast Main Line (WCML) and the Great Western Main Line (GWML).
Since HS2 was announced, critics of the project have often cited additional upgrades to the Chiltern Main Line as negating HS2. As a secondary main line between London and Birmingham (the same two cities as HS2 Phase 1 links), without any examination it seems as if this is slightly logical. Further examination of both projects shows how flawed a view this is.
Electrification
The Chiltern Main Line is one of the few InterCity routes in the UK to have no electrification. Electrification does have benefits. As a rule, electric trains accelerate more rapidly than diesel versions, which means that capacity is increased and journey times reduced. Given that the Chiltern Main Line is mainly a double track railway with a mixture of stopping and express services, this would be beneficial to the railway from a timetabling point of view. There are also the environmental positives to consider. The Taxpayer's Alliance explain that this, along with 26 other projects, would be a good replacement for HS2.
However, there are problems. Firstly, the branch to Aylesbury shares track with the London Underground which is 4th rail electrified. No main line railway in the UK is electrified in such a manner, and for good reason. 4th rail is only good for low-speed light rail operations (like the tube). 3rd rail electrification is off the table too. The Office of Rail Regulation (ORR) and the Department for Transport (DfT) have effectively ruled out any new stretches of 3rd rail electrification on safety grounds. Essentially, the work required to demonstrate that the risk of new third rail installations can be sufficiently mitigated, and that any additional risk compared to other traction solutions is more than offset by other benefits means that any new 3rd rail electrification is not going to happen. Additionally, if one electrified the Chiltern Main Line with 3rd rail, it would be 'out-of-place' with the rest of the rail network that it interacts with (the GWML at Oxford and Banbury and all electrification in Birmingham all has overhead electrification). One could switch from one to the other, but that would make the rolling stock and project needlessly expensive. Dual-power with both 4th rail and OHLE may be possible, but dual-power electrification of any section is expensive and wasteful. There may be engineering barriers (I don't know enough to comment properly).
One could argue that one should keep the London to Aylesbury line diesel (and only electrify the Chiltern Main Line proper), but, given that the Taxpayer's Alliance video I mentioned earlier was filmed at Stoke Mandeville (on the London to Aylesbury line), they cannot really put the Chiltern Main Line electrification argument forward without explaining how this problem will be addressed.
Additional Tracks?
Although the Chiltern Main Line has been almost completely re-doubled, it is still not in the state it was in prior to rationalisation. Several stations used to have passing loops and other sections used to be 4 track for some distance. In order from London, these are:
- Wembley Stadium (passing loops)
- South Ruislip to West Ruislip (4 track)
- Denham (passing loops)
- Gerrards Cross (passing loops)
- Beaconsfield (passing loops)
- High Wycombe (passing loops)
- Princes Risborough (passing loops)
- Lapworth to Tyseley (4 track)
Some of these would increase capacity. The 4 track sections are especially useful because it allows trains to overtake while not making the slower train stop.
Why These Improvements do not Negate HS2
Let's say that we managed to carry out all these improvements. Why does this mean HS2 is still required?
Although I said that electrification increases capacity, it doesn't do it by that much. It certainly wouldn't mean that the Chiltern Main Line could take anything like the number of additional services that HS2 will take when fully completed. Passing loops don't create as much capacity because the slower trains require paths into and out of the loops, and they are stationary for at least 5 minutes at the loop. Additional capacity created would likely be used up to provide additional stopping services to the underserved commuter stations between London and Banbury, or between Dorridge, Stratford-upon-Avon, and Solihull into Birmingham.
These improvements only take into account Phase 1 (London to Birmingham) and not Phase 2 (Birmingham to Manchester/Leeds etc.). HS2 is often accused of being London-centric, so any ideas of alternative schemes to solve the problems that HS2 tries to solve fall into that narrative and are thus partially useless.
Finally, this fundamentally misunderstands what HS2 is. These improvement plans assume HS2 is about making journeys between London and Birmingham faster. It is not. HS2 is about creating additional capacity for the places where there is no additional capacity available. Electrifying and improving the Chiltern Main Line will not be of any benefit to the main capacity problems that HS2 will solve (listed and explored in detail
here). Improving the Chiltern Main Line must be done in addition to HS2, not instead of it. That is a problem that the 26 other projects outlined by the Taxpayer's Alliance also share. Few of them even address the problems that HS2 solves, and the ones that do only look at one of the problems and do not solve it as comprehensively as HS2. Merry Christmas.