HS2 Forecasting – not “the highest standards of evidence.”

This is from a letter by Bruce Weston of HS2 Action Alliance to the Department for Transport. Reproduced with permission

A Department for Transport spokesman told the Telegraph:

“Our modelling has been calculated using conservative assumptions and a well established approach to demand forecasting that is recognised across the transport industry, and that conforms to the highest standards of evidence.” Telegraph 3 December 2011

Your Department’s modelling is far from conforming to the ‘highest standards of evidence’ as the modelling is based on out of date forecasting factors. The version of Passenger Demand Forecasting Handbook used (4.1) is importantly out of date in regard to the income elasticity distance growth factors. These cause DfT’s model to overestimate long distance rail demand compared to the current version (5.0). The treatment of the distance term, ie its exclusion, has been confirmed by a major study conducted by Oxera and Arup. Your Department has refused to release the report from this study in response to an FOI request, but this particular result was presented to a transport economists group in February 2011.

In fact when Philip Hammond came to office in 2010 he inherited a draft Tag Unit (3.15.4d) that was to reduce these distance terms as a temporary measure [1] on the basis of an explicit recognition that the version 4.1 values are wrong. A full revision awaited implementing the outcome of the Oxera Arup work. The recommended maximum values in the draft guidance are lower than those used for HS2, and would have resulted in forecasting lower demand.

The draft guidance was due for adoption in April 2010. To date the draft has not been confirmed as guidance, nor has the version 5.0 approach been adopted, nor has the Oxera Arup research been published nor acted upon.

This falls well short of my concept of conforming to the ‘highest standards of evidence’.

[1] Unit says:
‘4.2.9. We agree that the PDFH 4.1 recommendations produced unfeasibly large elasticities over long distances. However, in light of the ongoing research described above we are reluctant to suggest
changes to our demand forecasting methodology that may be superseded within a matter of months. As
way of compromise we recommend that PDFH 4.1 elasticities continue to be used but that a maximum
limit is placed on the elasticity value, in line with most practitioners use. In the absence of further
evidence we suggest limits of 2.5 (to London) and 1.5 (from London). Should promoters wish to use the
PDFH 5.0 elasticities then they may do so as a sensitivity test to this core analysis.’

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2 comments to “HS2 Forecasting – not “the highest standards of evidence.””
  1. Pingback: STOP HS2 | Embarrassed DfT create spurious statistics

  2. Thanks Bruce! I am shocked to know that they are hiding correct information to dupe everyone! It’s not hard to know rightaway that this project is a waste of money and time. It’s just not worth the effort to save that 20+mins journey time from Birmingham to London (anot so demanding journey) by causing so much damage/disruption to people’s lives, wild lives and environment. Our country is in 1T deficit while the Government is cutting funding everywhere incl. NHS and Education. What exactly is their priority? Health vs Train?? What is wrong with them? I started to wonder if there is any under-the-table deals going on in there. We need public enquiry and proper review. I don’t trust them. Now knowing that they can’t even read reports!! Why exactly these people are running our country?

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