Select Committee on the Crossrail Bill Minutes of Evidence


Examination of Witnesses (Questions 12380 - 12399)

  12380. LORD BROOKE OF ALVERTHORPE: Mr Berryman was saying that during the construction they could either use electric battery-motivated engines or, alternatively, diesel engines. Do you know the difference in decibels between one and the other?

   (Mr Thornely-Taylor) Can I first make it clear that what Mr Berryman was referring to was the small, narrow-gauge, temporary trains that run on the temporary construction railway. Yes, there is a reduction in noise from battery locomotives compared with diesel locomotives. It is not necessarily a straightforward matter to choose one or the other because the distance that has to be travelled by the temporary railway is one of the many things that determines the choice of locomotive, and I do not think we have the opportunity today or at the present time to say that it should be a battery loco or a diesel loco, but there are important operational and other demands that lead to the choice of the appropriate locomotive.

  12381. But, wherever possible, it would be beneficial to use the battery-operated one from a noise point of view?

   (Mr Thornely-Taylor) It would, although these are small locomotives. They do not have high noise levels. I did quite a lot of work on the equivalent construction locomotive on the Channel Tunnel as opposed to the Channel Tunnel Rail Link, and they are relatively small units.

  12382. What kind of category? What kind of figures?

   (Mr Thornely-Taylor) They would be substantially quieter than even the new re-engined, quieter high-speed trains coming out of Paddington. They would be no noisier, in fact quieter than a diesel multiple leaving Paddington. They are, I stress, one single locomotive—

  12383. Would it be 50 or 70?

   (Mr Thornely-Taylor) The sound level?

  12384. Yes.

   (Mr Thornely-Taylor) The measurements are normally made at standard distances. At 7.5 metres from the railway, you could expect a figure below 80. A Class 66, which is a mainline freight locomotive, hauling full-sized freight trains, probably the quietest mainline locomotive, is about 80 at 7.5 metres and I would expect the temporary railway locomotive to be less.

  12385. So it is still quite noisy?

   (Mr Thornely-Taylor) It would still be audible, yes, my Lord.

  12386. CHAIRMAN: Now, Lady Bright, would you like to ask any questions?

Cross-examined by LADY BRIGHT

  12387. LADY BRIGHT: Thank you very much for your intervention, my Lord. That was helpful in terms of explanation. I would just point out that we have the Class 66s and those are the things that shake Mr Hessenberg out of bed! Those are the freight trains that are used, so 80, yes, is noisy. Thank you, Ms Lieven, for clarifying that point also about the regulations; that is a comfort. Mr Taylor, I wonder if you could explain, because I am not sure that we have all got it completely, about this one decibel and how easy it is to measure in a complex environment, a noisy environment, with accuracy that one decibel.

   (Mr Thornely-Taylor) It is almost impossible to measure it accurately. The procedure is purely one of calculation. There is a procedure designated by the regulations published by the then Department of Transport called `Calculation of Railway Noise', a volume which contains both the data and the method for doing the statutory calculations. The procedure is followed according to set rules and, I am pleased to say, if four completely different experts all sat down to do the same determination for the same location, provided they made no errors, they would all get the same answer and, because it is a calculation procedure, it is capable of resolution into these small margins. A small margin is necessary to make quite sure that eligibility for statutory noise insulation does not arise wrongly or accidentally in a case where there happens to be an altered railway, but it really makes no difference at all to the noise climate, so it is important that, where there is eligibility for noise insulation, it really can be clearly attributed to the new, or altered, railway, and that is the procedure which will be gone through for Crossrail.

  12388. But you could not measure that one?

   (Mr Thornely-Taylor) No. Two sound level meters can measure different levels differing by more than one decibel and still meet standards for sound level meters.

  12389. So the calculations are theoretical because we are talking about feeding in data, are we, that does not yet exist?

   (Mr Thornely-Taylor) That is quite correct.

  12390. They are all predictions, are they not?

   (Mr Thornely-Taylor) Yes. This is strictly for eligibility for operational noise insulation.

  12391. The detailed noise study that is going to be undertaken you say will take account of all the noise sources, will it not?

   (Mr Thornely-Taylor) Yes, it will.

  12392. Does it not seem sensible that that data should be available to the makers of all the noise sources? Will it be available? Will this be a public study?

   (Mr Thornely-Taylor) That noise study will be publicly available, yes. That will be carried out as part of the processes I described before lunch, primarily in the context of the construction noise evaluation both for the section 61 process and for considering whether this is eligibility for noise insulation or temporary re-housing under Information Paper D9. The output of all that work will be a public document and available to all.

  12393. Excellent. Do we know that it will contain all the data required? If, for example, Transport for London, which is going to wholly own Crossrail very shortly, the reorganisation is under way, wanted to find out how much of the noise was due to their Westway and how they could best remediate that, would they be able to use this data for that purpose?

   (Mr Thornely-Taylor) They could, but they could do that in two or three days' time when the new noise maps come out because there is a separate map for highway noise. We saw on the exhibit before lunch a blue corridor either side of the Westway due to the high noise from traffic on that road and that is pure traffic noise and then in a few days' time there will be a rail noise map which will show pure railway noise and it will be possible for Transport for London and everybody else to see the relative contributions of the two sources.

  12394. Would they be able to feed in various hypotheticals into the model?

   (Mr Thornely-Taylor) Yes indeed. The models are completely mechanistic, so if you feed in different traffic volumes and different rail vehicle types you get the appropriately different answer. In due course the noise maps will be revised and updated, although that will not be for several years yet.

  12395. I am having a problem conceptually about "It's my noise not your noise" because we do recognise that the cumulative effects of noise are complex to assess, are they not?

   (Mr Thornely-Taylor) They are indeed complex. It is quite true that two noise sources do combine to produce a higher level, but as I explained to the Committee right at the outset in my talk on Day One, that effect is remarkably small in that combining two identical noise sources only pushes the noise level up by three units. If we waved a wand and created an identical Westway on, as near as possible, the identical alignment, surprisingly the noise climate would only worsen by 3dB. You would notice it but only just.

  12396. Would you agree that it is likely—we cannot predict because we do not know, we have not got the data yet—that this complex noise environment will be experienced differently at different locations even on this short street?

   (Mr Thornely-Taylor) That is very true. We have already seen how the existing railways are at different levels, e.g. the Hammersmith & City Line is diving down. On the site visit some of us will have heard the very different kind of noise that the Hammersmith & City Line makes because of its jointed track from the diesel hauled trains going underneath the bridge that we also heard. They are all different in their nature. It might sound odd but from that point of view the presence of continuous rather characterless noise from Westway which Sir Keith described as "white noise", meaning it was a broad band characterless noise, to some extent smoothes over some of the more irritating characteristics of, for example, the Hammersmith & City Line clickety-clacking over its jointed track.

  12397. They are different noises. Would you also accept that exposure to them over a long period will have differential effects as well?

   (Mr Thornely-Taylor) Complex effects. There is some habituation to noise. I am sure if we did a social survey of the corridor from Paddington to Ealing Broadway we would find a wide range of responses. Some people would say they had got used to the railway noise and it did not disturb them; other people would say that it was a major source of disturbance, it prevented them sleeping and you get a wide distribution of responses whenever you look at public responses to a complex noise source as this.

  12398. Is it not the case that these really rather complicated tools for measuring noise are at least partly, if not primarily, designed to predict the point at which the human at the receiving end is going to start making complaints?

   (Mr Thornely-Taylor) No. Humans are an important part of it, but there are many reasons for considering noise: effects on sleep disturbance, effects on health, effects on task performance concentration, learning. There are many effects noise has. Complaint prediction is but one and indeed there are tools for doing that, but that is only one of many.

  12399. I mentioned it really because it indicates, does it not, that there is a degree of subjectivity in all this?

   (Mr Thornely-Taylor) There is a wide degree of subjectivity and one has to address that by considering populations, groups of people, groups of residents as a statistical sample and you end up with a familiar distribution curve with insensitivity to noise at one end and sensitivity at the other end. If you take single figures out of that like average annoyance or a particular percentage of people highly annoyed, there are ways of getting a single number which does not change from a population among which the individual human responses vary enormously.



 
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