The difference in disruption
According to the government’s Response to the House of Lords Economic Affairs Committee HS2 report, “upgrading the existing railway is extremely disruptive to existing rail services compared with building a new line”.
[HS2: Government Response to the House of Lords Economic Affairs Committee, July 2015]
[…] Lord [Andrew] Adonis described the £9bn West Coast Main Line upgrade completed in 2008 as “performing open heart surgery on a moving patient”.
In July 2009, it was Andrew Adonis who announced a “£1 billion” upgrade of an existing main line — Great Western electrification. But the earlier West Coast Route Modernisation (WCRM) was primarily about renewal of worn-out assets, not an upgrade.
Altogether, Network Rail is spending £5 billion on modernising the Western route, but its renewals-to-enhancements split is not clear. The Great Western’s upgrade element must surely be higher, because there is no overhead line equipment being “renewed”.
Andrew Adonis has never explained why upgrading the Great Western is “the right thing for the country”, but upgrading the West Coast line is “open heart surgery”.
Furthermore, the HS2 high speed rail scheme depends on upgrades to the existing West Coast line (for example, to strengthen power supply for ‘classic compatible’ trains).
Claims about the extent of disruption caused by upgrading the existing railway are best treated with caution. During West Coast modernisation, miles of worn running rails were replaced by new rails of heavier profile (so the track was ‘upgraded’). Had they been replaced on a like-for-like basis (i.e., renewal without upgrade), the disruption involved would have been essentially the same.