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.
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