From mid 2025 document:
Instead of high-speed rail
Northern transport schemes that will work
As No10 transport adviser, the author repeatedly asked for evidence
that the WCML would soon be full, but was never given any. Avanti
West Coast runs 48 trains every weekday from Manchester to London,
providing just over 27,000 seats in this direction each weekday. The
Office of Rail and Road, the regulator, says that in 2023/4 there were
3.4 million rail journeys between Manchester and Camden (the London
borough in which Euston, the WCML terminus, sits.) That is an average
of 9,300 per day.
...
...
Thus across the average day only about a third of the service’s current
seating capacity from Manchester to London is used. At 2 per cent growth
per year, it would take 53 years, not the claimed 12, to fill it. Of course,
more passengers will join at intermediate stops (though Manchester is by
far the busiest); some trains will be busier than others; there are slightly
fewer trains at weekends; and about 4,700 of the 27,000 seats are first
class, though first class passengers are also included in the 9,300 daily
total.
The figures clearly do not, however, support any claim that the WCML
is full, or nearly full, or is going to be full any time soon. Indeed, some
services on the line have recently been reduced (the number of fast trains
from London to Birmingham has been cut by about a third since 2019,
for instance.)
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An analysis based on Office of Rail and Road figures for 2023/24, the WCML is not at full passenger seating capacity. On average, only about one-third of the current seating capacity on services from Manchester to London is utilized. The figures provided suggest it would take 53 years, at a 2 percent annual growth rate, to fill the current capacity between Manchester and London. More information is available on the Office of Rail and Road website.