Gladiatorial games, part 26

(… continued from Gladiatorial games, part 25, posted on 30 Apr 2016).

I mentioned in part 24 of this blog series that Doug Sharps, expert witness on acoustics for the HS2 Action Alliance, had raised some issues with the HS2 Select Committee that his professional colleague Rick Methold, put up by Chiltern District Council, had not covered, and that there were two in particular that I wished to review. Having examined the first of these in the preceding two parts of this series, I will now take a look at the second (see footnote 1).

This second issue is the threshold levels that HS2 Ltd has specified for the significant observed adverse effect level (SOAEL) and, more specifically, the relationship of those threshold values to the lowest observed adverse effect level (LOAEL) values.

By way of a reminder, the value specified for SOAEL is important to affected residents because one of the “noise policy aims” of the Noise Policy Statement for England (NPSE) is to “avoid significant adverse impacts on health and quality of life”. By definition, this means avoiding exposing residents to noise levels that exceed SOAEL. However, before we get too excited about this prospect, the gilt is decidedly removed from the gingerbread by the accompanying caveat “while also taking into account the guiding principles of sustainable development”, which basically means you don’t have to avoid it if it is too difficult, or it costs too much. Notwithstanding, SOAEL is important because the NPSE regards noise that is below the SOAEL, but above the LOAEL, thresholds as “adverse” and the NPSE aim then is only to “mitigate and minimise” rather than “avoid”. Whilst this is, at least on the face of it, a clear distinction if the SOAEL threshold is exceeded, the clarity of the difference is somewhat blurred by the sustainable development get out of jail free card being in play (see footnote 2).

Mr Sharps explained his gripe to the HS2 Select Committee in the following way (see footnote 3):

“In my opinion, the significant adverse effect levels should be 10dB above the low observed adverse effect levels, not the 15dB for LAeq or the 20-25dB for LAmax that HS2 propose. The 10dB is a doubling of loudness, a much higher level; and HS2 adopt this 10dB difference between low levels of impact and significant levels of impact in the construction noise criteria which are in E23.”

The numbers behind Mr Sharps’ remarks may be easily verified by referring to the two HS2 Ltd information papers E20 and E23. The former informs us that, if we employ LAeq to operational noise, SOAEL daytime is set at 65dB LpAeq,16hr and the equivalent LOAEL is 50dB; at night SOAEL is 55dB LpAeq,8hr and LOAEL is 40dB – so that is 15dB difference in both cases, as Mr Sharps claims. At night we have the choice of employing LAmax and, in this case, SOAEL is either 85dB LpAFMax or 80dB LpAFMax, depending upon whether the number of nightly train pass-bys is above or below twenty; the equivalent LOAEL is 60dB LpAFMax, irrespective of the pass-by rate – so the difference is 20-25dB, agreeing with Mr Sharp (see footnote 4).

Delving into E23 reveals that the SOAEL thresholds set for construction noise vary from 65dB LpAeq,T to 75dB LpAeq,T, depending upon the time period during the day and evening, with the corresponding LOAEL a uniform 10dB below in the range 55dB LpAeq,T to 65dB LpAeq,T – all as claimed by Mr Sharps (see footnote 5).

What Mr Sharps was seeking was for this 10dB margin to apply to all construction and operation thresholds, rather than having different margins between LOAEL and SOAEL, an arrangement that he described as “illogical” (see footnote 6). Mr Sharps’ plea for “a logical matrix of assessment criteria” did not appear to find favour with the Promoter’s expert witness on acoustics, Rupert Thornely-Taylor, despite his concern, expressed on another occasion and in connection with a different issue, that the setting of LOAEL and SOAEL threshold values should not result in an “odd looking framework” that “doesn’t make sense” (see footnote 7). As it turned out, with the exception of a single comment about the source of the 55dB LpAeq,8hr SOAEL that I will refer to in part 27, Mr Thornely-Taylor left making the counter-arguments on the SOAEL/LOAEL relationships to the Promoter’s Lead Counsel, Tim Mould QC, during his cross-examination of Mr Sharps.

In my view legal cross-examination can all too often serve to obscure, rather than expose, the truth. It is an adversarial process that requires Counsel to be an interrogator, rather than a facilitator, and often causes the witness to be overly defensive and unwilling to volunteer information. Unfortunately, this typical behaviour appeared to govern the discussion about the SOAEL/LOAEL relationships that the Select Committee witnessed, and I don’t think that much illumination was achieved. However, I will use my next posting to report upon what was said.

(To be continued …)


  1. The evidence presented by Mr Sharps was heard during the afternoon session of the HS2 Select Committee that was held on Monday 12thOctober 2015 (video and transcript).
  2. See paragraphs 1.7, 2.23 and 2.24 of the NPSE.
  3. See paragraph 50 of the transcript of the afternoon session of the HS2 Select Committee held on Monday 12thOctober 2015.
  4. Refer to Table 1 in Appendix B to HS2 Ltd publication High Speed Two Information Paper E20: Control of airborne noise from altered roads the operational railway.
  5. Refer to Table 1 in Appendix A to HS2 Ltd publication High Speed Two Information Paper E23: Control of construction noise and vibration.
  6. See paragraph 78 of the transcript of the afternoon session of the HS2 Select Committee held on Monday 12thOctober 2015.
  7. Refer to the fifth paragraph of my report in part 18 of this blog series. Mr Thornely-Taylor’s quotes are taken from paragraph 22 of the transcript of the afternoon session of the HS2 Select Committee held on Wednesday 4th November 2015.

Acknowledgement: I wish to thank Michael Woodhouse for his suggestions and comments, which I have found invaluable in preparing this series of blogs.

Important Note: The record of the proceedings of the HS2 Select Committee from which the quotes reproduced in this blog have been taken include uncorrected transcripts of evidence, which are not yet an approved formal record. Neither witnesses nor Members have had the opportunity to correct the record in such instances, and it may therefore be subject to changes being made in the light of any such corrections being requested.







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