Select Committee on the Crossrail Bill Minutes of Evidence

Examination of Witnesses (Questions 12400 - 12419)

  12400. If your aim were to ensure that there were no material worsening of the noise in the environment as a result of your railway you are actually going to have to put in something or a series of measures that are a little bit generous in their assessment in order to cover all the effects, are you not, on individuals?

   (Mr Thornely-Taylor) The procedure is fairly clear, it is to define a methodology, which was done right at the beginning of the environmental assessment work and to set a threshold of a significant effect. Then it is to see whether the noise that is associated with the development you are assessing will trigger the significant effect. If it does not then no action follows and that is what has happened in the case of Crossrail in this location, there is no significant effect from the operation of Crossrail in this location.

  12401. Would you accept our rather crude description of the situation that, using the data which was gathered a long time ago in the Environmental Statement, the Crossrail trains will be broadly inaudible to us but that you anticipate that this will not be the case when the new data is collected?

   (Mr Thornely-Taylor) It has never been part of the process to assess audibility. That is a wholly subjective concept in environmental noise.

  12402. Sorry! It was a loose term.

   (Mr Thornely-Taylor) It is this process of determining a threshold of a significant effect. Let us be quite clear, there can be a noise, which is a new noise, which is not assessed as a significant effect but which is still quite clearly audible. Nobody is suggesting that on the morning that Crossrail services start it will be impossible to tell if it has happened. The trains will sound different and they will have slightly different characteristics. I am reminded that when the Tyne and Wear Metro first opened after a gap when there had previously been diesel multiple units running on the same line people noticed that the new vehicles had six axles per unit instead of four axles and hearing this different duration between the passage of bogeys made them notice the new railway because it was different, but the noise levels had not changed significantly and it was not a signature effect, but it would be wrong to say it did not pass unnoticed.

  12403. Therefore, it was not a significant effect according to the calculations but it was a significant effect according to the recipients?

   (Mr Thornely-Taylor) Some recipients had their attention drawn to the fact that it was a different noise and it attracted interest but it remained below the threshold of significant effect using the well-established system that is used in all environmental assessments.

  12404. Would you accept that there is a great difference between a very intrusive noise once every five days, as you might get with a freight load at four in the morning, and 24 trains an hour?

   (Mr Thornely-Taylor) They are very different, yes.

  12405. Would this be picked up in this sort of crude measurement?

   (Mr Thornely-Taylor) Yes.

  12406. It would not be picked up in the trigger, would it?

   (Mr Thornely-Taylor) Yes. All operational train noise is taken into account in the process.

  12407. Obviously one is a peak noise and one is an ambient noise. I am talking more about the effect on the people.

   (Mr Thornely-Taylor) To the extent that the noise of a freight train might have more annoying characteristics than the noise of electrical multiple units, there is no special allowance for that. As was observed this morning, electrical multiple units are very benign in their noise characteristics. The noise is almost all wheel-rail interaction, there is very little traction noise and certainly no diesel engines or anything of that kind. Noise for noise, an electric multiple unit is likely to be less disturbing than, for example, a freight train.

  12408. I shall remain worried about that one decibel that had to be fed into the calculations. It all seems too close for comfort. We are here with the Bill going through with no certainty on that one. I would like to move on to the hierarchy of mitigation that was discussed on Day One. The most desirable kind of mitigation is at the noise source. If it is going to work you will try to do it at the railway level, is that right?

   (Mr Thornely-Taylor) Yes. It is a sort of mantra in noise control that source, path and receiver is the order in which you attempt to mitigate noise.

  12409. This hierarchy of litigation is broadly to move from one close to the source of the noise and further back until your last ditch is sound insulation, is that correct?

   (Mr Thornely-Taylor) I do not know whether it is last-ditch, but being the receiver, it is the receiver part of the source path receiver chain.

  12410. If the aim is to achieve a certain degree of mitigation you could use several of these layers of mitigation. They are not mutually exclusive, are they?

   (Mr Thornely-Taylor) They are not.

  12411. Let us turn to the barrier. We do not wish to argue any more about the wall and I am not going to ask you engineering questions. Bearing in mind the vulnerable area is the gardens, we are probably going to have to retreat from the front gardens altogether if we do not get a barrier on the street side, but we must protect at least the back gardens in the rest of the Conservation Area. I am not assuming at this point that you are right or wrong about the effects of Crossrail noise on that. We should not make that assumption until we have got this new detailed noise study. I would like you to say in theory if you decided to move your line of retreat back because the wall was for various reasons not a fair one, could you make the row of houses an effective noise barrier if you stopped up the gaps between them?

   (Mr Thornely-Taylor) That is not an option which any transportation scheme promoter could ever do because of all the complexities of property ownership and Town & Country Planning and all the other many reasons why it would be completely impractical

  12412. If such a scheme could be devised and a way of doing it could be devised it would be a pretty cheap option, would it not?

   (Mr Thornely-Taylor) I do not think so. I think everyone would want something different. All the local requirements, both structurally and from an administrative point of view, would be so different that I think it would be a complete nightmare.

  12413. It is possible and I would not prejudge that; it depends on whether people wish to go in the same direction and find a sensible solution or not, but acoustically it is a goer.

   (Mr Thornely-Taylor) Acoustically, yes.

  12414. And, in terms of materials and so on, inexpensive.

   (Mr Thornely-Taylor) I think a piece of engineering would need to be done to see. The ordinary hum-drum things we were talking about this morning, like wind-loading, become enhanced in gaps between houses. I have seen more garden fences blown down in recent times than almost any other structure, and I think a quite significant engineering exercise would have to be undertaken before I could answer that question.

  12415. Perhaps we will ask somebody else about that, because it is a major engineering exercise, although, perhaps, not as major as some of the engineering exercises you will be engaged in on the railway. Thank you, that is helpful. I would like to simply ask if we should keep that in play; prejudge nothing until we have the noise data, really, in terms of what might be the appropriate remedy. Do you not even exclude the wall, would you say?

   (Mr Thornely-Taylor) The existing wall is a noise barrier—let us not lose sight of that—and it does contribute to lower noise levels at Westbourne Park Villas than would exist were it not there, and it is quite possible that is one of the reasons why it was built (no doubt trespass and other things came into it when the Edwardians—or whoever they were—built it) and there would have followed from its construction a reduction in noise. Once you have got a noise barrier the law of diminishing returns comes in and you do not go much further by adding to it. We have seen that you have to do a lot to it with major engineering consequences at great cost to improve upon it significantly.

  12416. But it is fairly effective to its own height, in effect, as a noise barrier. Correct?

   (Mr Thornely-Taylor) It is a 2.5-metre high brick wall which results in much better noise conditions than there would be without it.

  12417. At least hypothetically, and I will leave it after this, if you deal with height with the existing wall you find can ways of dealing with the other heights, and your last ditch is the noise insulation.

   (Mr Thornely-Taylor) It is not "last ditch"; it is the logical course that comes from a consideration of the options, both in terms of practicability, cost-effectiveness, legal requirements and proper planning of a major transportation project.

  12418. I will leave that line of questioning there, thank you, as long as we can agree that the options must remain open until the detailed noise data is available. I am glad to hear that it is going to be publicly available and can be used by the Promoters to see what would be useful remedies for them to do for different noises that are not Crossrail's.

   (Mr Thornely-Taylor) Yes. No information will be withheld from the public that is not classified.

  12419. LADY BRIGHT: Thank you very much indeed.

previous page contents next page

House of Lords home page Parliament home page House of Commons home page search page enquiries index

© Parliamentary copyright 2008