And, by the way, there’s also …

Assessing the annoyance caused by HS2 noise, part 5

This is the final blog in this short series on how I think HS2 Ltd should improve how it is proposing to estimate the annoyance that noise from HS2 will cause.

I explained in my blog How annoying is that? (posted 18 Oct 2012) that a noise threshold should be chosen for any noise parameters at the level that will just cause annoyance to the selected proportion of the population. I explained in my blog A summit that is far too high (posted 26 Oct 2012) that the threshold that had been specified by HS2 Ltd for the peak noise level of a single train pass-by did not appear to satisfy this requirement.

So what about the threshold that has been chosen for the equivalent continuous sound level parameter, LAeq,16hr?

This threshold level is specified as 50 dB for the 16-hour “daytime” period in paragraph 14.3.26 on page 153 of the document HS2 London to West Midlands EIA Scope and Methodology Report. This choice dates back to the HS2 London to the West Midlands: Appraisal of Sustainability (refer to paragraph 6.1.7 on page 49 of Appendix 5), where is was justified (in paragraph 6.1.6), as follows:

“The World Health Organisation, in its 1999 Noise Guidelines report in 2000 on states ‘to protect the majority of people from being moderately annoyed during the daytime, the outdoor sound level should not exceed 50 dB LAeq.’”

The Appraisal of Sustainability does not tell us where to find the quotation in the World Health Organisation’s Guidelines for Community Noise (here), but I can tell you that it is in Section 4.3.1 on page 43. HS2 Ltd may have hoped that nobody searched out the source because the full quotation from the World Health Organisation (WHO) is:

“To protect the majority of people from being seriously annoyed during the daytime, the sound pressure level on balconies, terraces and outdoor living areas should not exceed 55 dB LAeq for a steady, continuous noise. To protect the majority of people from being moderately annoyed during the daytime, the outdoor sound pressure level should not exceed 50 dB LAeq. These values are based on annoyance studies, but most countries in Europe have adopted 40 dB LAeq as the maximum allowable level for new developments (Gottlob 1995). Indeed, the lower value should be considered the maximum allowable sound pressure level for all new developments whenever feasible.”

I’m not sure, reading this, that the WHO feels that 50 dB provides an adequate annoyance threshold.

It seems reasonable to expect that HS2 Ltd would pay regard to the advice of the Department for Transport (DfT), as set out in the DfT’s Transport Analysis Guidance (WebTAG). Paragraph 1.4.8 on page 6 of Unit 3.3.2 of this document says:

“It is also important to be aware that the annoyance response function is uncertain at low noise levels (especially over large distances). Consequently, it is recommended that appraisal is undertaken for noise above a cut-off level below which only a small percentage of the population would be annoyed. Research conducted by the Department suggests a positive willingness to pay to avoid transport related noise from 45dB LAeq,18hr, and this level is used as the cut-off for both annoyance and valuation calculations.”

I also feel that in setting the threshold HS2 Ltd has failed to take due account of the very tranquil nature of many of the areas through which HS2 will pass; a failure that I mentioned this in my blog It used to be really quiet ‘round here (posted 12 Oct 2011). In this respect, HS2 Ltd appears to have forgotten its own aspiration in paragraph 8.5.2 on page 53 of Appendix 5 of HS2 London to the West Midlands: Appraisal of Sustainability:

“A mitigation strategy that takes into account the relative importance of different factors affecting relative tranquillity, as identified in the CPRE/NU study and mapping, could help to reduce the potential impacts.”

There is no evidence that such a strategy is being employed in the way that the threshold level has been selected and, accordingly, how impacts will be assessed.

I suggest that it essential, in the light of these comments that HS2 Ltd reviews the equivalent continuous sound level parameter threshold choice, and provides a properly documented and evidenced justification for this choice.

There is one further matter that I feel that I ought to refer to at this juncture, although with not much expectation of a successful outcome. This matter is whether the application of A-weighting to the sound parameters is appropriate for noise from very high speed trains. I discussed this issue in my blog A weighty matter (posted 26 Jun 2011) and said there that this weighting network, which is the result of research in the 1930s, had been in widespread use since the 1950s; it is for this reason that I doubt that my comments will overcome the professional inertia that has kept its use ubiquitous.

However, in my blog I quoted extensively from an excellent review paper that doubts the efficacy of using A-weighting in applications like high speed train noise and was able to demonstrate support for this view from no less an authority than the WHO. I am concerned, in particular, that the attenuation of low frequencies inherent in the use of A-weighting will under represent the contribution that aerodynamic noise will make to noise nuisance. I think that HS2 Ltd should look at this, but fear that it will be ignored.

So it has taken me five blogs to set out, hopefully in an approachable and understandable fashion, where I think that HS2 Ltd is going wrong on its approach to estimating the annoyance that HS2 noise will cause. I have been attempting for some time to get HS2 Ltd to take part in a dialogue on these, and other, noise issues, but with no success whatsoever. Comments made about HS2 Ltd noise methodology, by me and others (including professional acousticians), in response to the public consultation last year and the recent EIA Scope and Methodology consultation have been either ignored by HS2 or have received only perfunctory and incomplete responses.

In its document Review of HS2 London to West Midlands Appraisal of Sustainability HS2 Ltd confirms that it is “aware of the concern communities that are alongside the proposed route for HS2 have regarding noise” (in paragraph 7.2.2 on page 26). It appears to me that the best way of addressing that concerns would be to talk to those communities freely, openly and honestly about the issues. Unfortunately, that does not appear to be the way that HS2 Ltd goes about its business.


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