(updated  31st August 2007)

Keywords: simulating people, simulating crowds, simulating crowd dynamics, workshops, House of Commons

Transport, Local Government and the Regions - Minutes of Evidence
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Here you can read the Minutes of Evidence which were ordered by the House of Commons printed 5 February 2002.

Present:

• Andrew Bennett, in the Chair

• Sir Paul Beresford

• Ms Oona King

• Mrs Gwyneth Dunwoody

• Chris Grayling

• Mrs Louise Ellman

• Christine Russell

Select Committee on Transport, Local Government and the Regions Minutes of Evidence

Examination of Witnesses (Questions 392 - 399)

TUESDAY 5 FEBRUARY 2002 - MR ANDREW ALLSOP, MR PETER BRESSINGTON AND DR JOHN ROBERTS

Chairman

392. Can I welcome you this morning, and ask you to introduce yourselves?
(Dr Roberts) I am a consulting engineer, a director with a firm called Babtie Group. I live in Manchester but I do a lot of work in London as well. I am here because I am the chairman of a committee which has been set up by the Institution of Structural Engineers; it includes members from most of the professions in the built environment, and it is going to provide advice to designers relating to tall building design, the safety of people in tall buildings, following the 11 September events in America.
(Mr Bressington) I am a director of Ove Arup & Partners. I am responsible for its fire engineering group. I am particularly interested in the events of 11 September. I chair Arup's extreme events task force, and we were set up to look at what happened and perhaps where the future takes us in terms of design of tall buildings.
(Mr Allsop) I am from Arup and am head of the wind engineering work that Arup is involved with.

393. Are you happy for us to go straight to questions?
(Mr Bressington) In terms of safety, we have heard talk and obviously most of the discussion has been around the feasibility and the desirability of tall buildings. From a technical point of view we are just talking about safety, and I do not think there are any reasons from a safety point of view that tall buildings should not be built; we just need to look at some of the issues.

Christine Russell

394. Could you tell the Committee whether you believe the collapse of the World Trade Center was effected by its structural design?
(Dr Roberts) The story on why it collapsed is not yet fully understood by the people who have been appointed in America to investigate it. The head of that team of investigators is a Fellow of the Institution of Structural Engineers of the UK, because it is a worldwide organisation, and he is a member of our committee, so we are getting some direct feedback from the investigations. All the signs are as you might expect that it is quite complex and there is not one single factor that caused the collapse of the buildings themselves. It is related to a combination of physical damage by the plane impact which did remove a portion of the structure; very severe fire—and most buildings, as Peter will explain in more detail, certainly buildings in the UK, are designed for fire from normal occupational hazards which are essentially burning paper and wood and other cellulose materials, and here a fire was delivered into the buildings from hydrocarbons which burn a lot hotter, so there was very severe fire going on in the building and buildings have fire resistance. This building had a defined fire resistance but against a cellulose type of fire, and the final collapse occurred by something that structural engineers would call progressive collapse, which is where a part of the building collapsing on to the part below it can trigger what you would call a pack of cards, in loose terms, type of collapse. We would call that a progressive collapse, where one or more floors falling on to a floor below can trigger an almost immediate chain-reaction collapse down to the ground, and that appears to be what happened

395. Is it true that our safety regulations, certainly after Roman Point and the disaster there, in the UK are already more stringent than in the States?
(Dr Roberts) I am very reluctant to say that. What is true is that, post the collapse of Roman Point in 1968—which, as I am sure people will remember, was triggered by a gas explosion in a very particular type of building, and that was a system-built block of flats which had on the evidence afterwards quite weak connections between all the pieces and which progressively collapsed down through about 22 storeys from an explosion quite near the top—that triggered a change in the UK building regulations which came in in the early 70s. There were a couple more collapses in 1973 and 1974 of some school roofs in the London area, in Camden and Stepney, and those regulations have been with us since that time and they serve to limit the effect of what is called disproportionate collapse from an accident. You have to guess what the accident might be. It is not just to protect against a gas explosion or a fire; it aims at producing robust buildings that will tolerate some quite unusual accident happening in them. Those regulations are in place for all buildings in Britain and have been since that time but I think it is a huge step to jump from that and say, "Oh, had this building been in Britain it would not have collapsed". I do not think that is a step you can take at all.

396. Do you have concerns about existing buildings in the UK that may be vulnerable to what you described earlier as progressive collapse?
(Dr Roberts) Yes, because buildings are not designed for an event of that magnitude or those sorts of events. We hope they will be robust to survive some of them or most of them, but I do not think there is any doubt that there are serious accidents that could affect some British buildings.

397. And is it premature to say yet whether or not you believe it would be possible to strengthen further the existing regulations in the light of what happened on 11 September?
(Mr Bressington) There are a few issues there. The structure robustness is one issue and the other, obviously, is fire and evacuation and management of those buildings. My feeling is that certainly people will look at the codes. The codes are really based on a fire which can happen in a building which you would associate with that occupancy, so it may well be there are more performance requirements in the codes. It therefore gives people the opportunity to look at specific buildings in different areas, whether structure or fire, and make decisions based on a performance criteria. For instance, if you need 45 minutes to clear a high rise building in terms of evacuation, you need to try to do that based on the tenability, so I think it will move that way. It may not be a prescriptive requirement but more of a guidance.
(Dr Roberts) Looking back, which is very easy to do with hindsight, is that in the UK buildings are required to have defined periods of fire resistance, as you have no doubt heard from some other evidence, (probably from manufacturers of fire resistant materials), and typically in the UK large buildings would be required to have two hours' fire resistance for the above-ground structures. First of all, it does not mean that the building will stand there for two hours in a very serious fire—it is a sort of guide as to how long it will last but it is not absolutely for sure that that will happen—and the other link that is missing is that there is not any requirement in the UK to ensure that you can get everybody out in two hours in a building with a two-hour fire resistance, and that missing link is rather worrying when you think about it.

Chris Grayling

398. If an aircraft hits the side of a tall building, as happened in New York, you get a catastrophic impact and fire but in the case of the World Trade Center buildings, given the number of people who worked in those buildings, a very large proportion of those in the building did get out. When the planes hit the building, a lot of the impact burst out beyond the buildings rather than being contained within it. If a plane were to hit a medium-rise building with much greater density within a geographical area, is there an argument for saying that an aircraft landing in a 20-storey building with a larger number of workers could have a greater impact on that building than a high-rise building?
(Mr Bressington) Potentially, the World Trade Center I would suggest was picked out because it was a symbol and they decided they would attack that. They could have chosen to attack a sports stadium where, in terms of trying to achieve their objective which is to kill as many people as you can, they would have achieved that end using that. So it is not just tall buildings with these incidents because a lot of this is to do with security, politics, and all sorts of other issues rather than design. Certain aspects have come out of the World Trade Center and obviously more will in terms of what happened there, and we just need to build on some of those points and perhaps use them in the future. I do not think it is to say that, because a plane flew into the World Trade Center it is the sort of thing that is going to happen every day of the week. Certainly a plane was also flown into the Pentagon and that building was quite resilient in terms of attack but it still did kill quite a few people.

399. So there is a danger that safety restrictions around tall buildings become focused entirely on September 11?
(Mr Bressington) Yes.

400. Can I ask you, Dr Roberts, to talk a little more broadly about safety regulations in relation to tall buildings without specific reference to September 11?
(Dr Roberts) One thing of interest is that the United Kingdom regulations do not really envisage very tall buildings, they have graduations in the rules that we have to follow for different sizes and different uses of buildings and those classes stop at a height of 30 metres, which is 100 feet, and which came, for historical reasons, from the City of London, where there was a 100 foot restriction. In the United Kingdom there is no differentiation between what steps you take as a designer if the building is 30 metres, say 10 storeys high, or anything higher. As we know there are buildings getting on for ten times as high as that here. That is the first point.

401. Do you think that should be changed?
(Dr Roberts) We need to think about that because of some of the essential features of particularly tall buildings. There are structural issues to do with wind, they have to be much stronger because they are much taller, which is probably the reason why the World Trade Center survived the impacts of the planes because the forces that came from the planes were less than it would have received during a storm of wind. It was not entirely unsurprising that it stood there with the impact, it was the fire that caused very severe damage. The issues about the height of the building are structural but they are primarily to do with means of escape and fire regulations that apply. We have heard the comment already that if you were wishing to take action against a lot of people you would probably land a plane, there are plenty of other things you could think of doing, but one does not want to go into too many of them in a lot of detail. Just to take an example that has been mentioned, every week there are 80,000 people sitting in Old Trafford, usually, it is a very easy target. The regulations for Old Trafford require that every single one of those people have to be able to be evacuated to a place of safety in eight minutes, otherwise it does not get a licence. There is no such requirement for buildings which have maybe not 85,000 people in them but a few tens of thousands of people. There are issues like that.

402. Should there be such guidance?
(Dr Roberts) When you say, "Will regulations change following September 11?", there is a danger of focussing on that, but on the other hand it has highlighted these issues. Most buildings have been designed to contain a fire and to evacuate people from the floor where the fire has occurred in the immediate adjacent one above. That is called phased evacuation. Almost always in Britain you are told not to use lifts during a fire. You probably read about the World Trade Center that if you tried to and evacuate that without using the lifts it would take over four hours, it would have taken over four hours to get everyone out by the staircases, there physically is not enough room and people just have to wait and walk down the stairs. If you cannot use the lifts there are buildings which have very long evacuation times if everyone wants to get out in a hurry. If buildings have to be fully evacuated for the whole building due to some emergency we need a complete re-think about the issue of what has always occurred in the past, which is to phase the evacuation and not use the lifts.

Chairman

403. Is it feasible to use the lifts?
(Mr Bressington) Yes, you can use the lifts under certain circumstance. This brings us probably to one of the main issues, the management of the building and the on-going management of the building. If you know, for instance, that there is likely to be an event and the operators of that building know that then you do have a certain amount of time. In the time you have then it is best, if you can, to use those lifts. The difference between using the lifts in an imminent event is the fact that the building has not been impacted, the power supply is there and there is no damage to the building so people could continue to use the lift until such a point that may happen. If you really want to make the lifts much more robust then they have to follow the same pattern as we do in the United Kingdom and other places for fire fighting lifts, which are actually contained in a two hour fire fighting shaft with back-up power supplies. Once you get into that sort of lift then, obviously, you have much greater security for people to escape. If do you not do that and the building has been impacted then you are down to using the staircases.

404. If you put a fire fighter's lift is it very expensive?
(Mr Bressington) I would say it is expensive in terms of floor area. It would make the building inefficient in terms of space if you had lots of those lifts. There are middle ways here. Certainly from what we know of the incident that happened in the World Trade Center, it is not just that, it could be any other type of terrorist action which may be threatened, if you can use a lift to get people out then you do not need to do that much with them. If you try to use lifts in an impacted building then you do have to take other design measures.

Christine Russell

405. Thank you, Dr Roberts, for giving me that assurance about Old Trafford because my son sits there every Saturday afternoon. Can I take you back to the fire risk and ask you if you can give the Committee your idea of what measures we could put in place to stop the spread of fires in tall buildings?
(Mr Bressington) In terms of conventional fires, a fire that you would normally expect in an office floor, a wastepaper bin fire or any sort of fire, my belief is that the measures we have in tall buildings are adequate for that now.

406. Do fire safety officers share your confidence?
(Mr Bressington) Yes, they do. If you look at office fires, particularly casualties and fatalities in office fires in this country it is very low, it is about 1 in 14 million per year for someone dying in an office fire. What you have in a tall office which you do not have in a smaller office building is a whole range of fire protection measures to contain a fire, that is sprinklers, fire compartmentation on each floor, you have pressurisation in the staircases to keep smoke out, you have fire fighting lifts so that fire fighters can have access without having to use staircases. There are a range of measures which are required in the codes for buildings. What we are talking about is this over 30 metres, and do we get into another level of needs or requirement or performance, let us call it.

407. What about materials? The materials that buildings are constructed of have changed rather dramatically since the 1930s when the current standards, in the main, were set?
(Mr Bressington) That is right. Manufacturers of passive measures will make a big thing of this. The other point is, since they came up with those calculations based on those fire levels things have moved on in terms of the fire measures. Sprinklers are required in these tall buildings.

Mrs Dunwoody

408. If you were to get a fire—aviation fuel is a classic example, you do not expect to have to deal with that—for any reason that was not what was expected, a normal office fire multiplied by five, what is important is clearing the building very quickly? Are we to assume in tall buildings you can continue to work on the assumption have you a certain amount of time? If that is not the case, what, then, is the argument against forcing the people that build tall buildings to put in the extra requirement for fire lifts and fire shafts. In the City of London, for example, in the Barbican, the Fire Service were very disturbed that above a certain area they were going to be unable to deal with a fire efficiently. I did hear, although anecdotally, they insisted on weights on the Penthouse capable of carrying helicopters, I do not know if that is right. If it is the case that we have to rethink it, ought we not to be doing it that way? What is the element that is most important, clearing them quickly or withstanding an extra sized fire?
(Mr Bressington) They are both the same.
(Dr Roberts) They are both the same. If you look at what happened in the World Trade Center the ultimate issue was that the whole building collapsed, therefore the robustness of the building is what really matters and fire protection is a means to an end to secure that while people are leaving the building. There are so many issues that have arisen. For example, when you leave a building here most fire precautions require you to stand directly outside it.

409. Not if you know anything about the emergency services!
(Dr Roberts) You do not have to move away because it has never been thought if you were outside it the building would collapse round you. There are all sorts of issues that come out from this question of whether the building can survive a long period. It is a bit misleading to think just in terms of the fire protection of floor or of certain materials, what matters is whether the building will stand for a long period. There are views that we should make the building ultimately able to withstand a full burnout fire, that whatever happens in it the frame of building will still be standing, even if it causes massive devastation within a number of floors.

410. I get the distinct impression developers would not be happy about that.
(Dr Roberts) That may be so, but it depends what is costs.

Chairman

411. You concentrated so far on the physical things, how far is there a now a psychological problem that has to be assessed in that an awful lot of people in tall buildings will have seen that film over and over again of those events and therefore their behaviour will be based on what they have seen on television rather than what is sensible in the buildings that they are actually in?
(Mr Bressington) That is very true. Most of the things we have been involved in in terms of talking to our clients, whether they are developers or tenants, or even people that work in buildings, is it is very much a people thing. People's behaviour has been, I think, modified. I think that there are some positives and negatives with that, the positive is that traditionally when people hear a fire alarm in a building often they do not move, they assume that it is a false alarm or someone is going to tell them to do something, so they sit there. That does not happen so much now, particularly if you are in a big building.

Christine Russell: It does in Portcullis House.

Mrs Dunwoody

412. It does in the House of Commons until the fire officer appears in full gear and says, "Excuse me, madam, this is genuine".
(Mr Bressington) Everywhere else except for the House of Commons. On the other side we talked about, and John mentioned it, phased evacuation. Phased evacuation is a system where in a tall building or even in a very large foot plate building, like a shopping centre, if there is a fire in one place you do not take everyone out because there are measures in place to deal with the fire and it may be a false alarm. For most fires and offices this is still the right way forward. Since the events of 11 September, if people are told because they are on the 10th floor, "Stay there, this fire is right up the top, do not worry about it", whether they will do that is another matter. I think what the owners and the operators of buildings are saying to us is, if that happens what is likely to result from that. What we have been looking at it studies using computer simulation to see how long it does take to get people out of a building, this can be an existing building or one yet to be designed. There is ways of getting a better feel for this. People's behaviour may change again because over time you get this anxiety wave and it may drop down again.

Mrs Ellman

413. Would the increased regulations needed to make higher safety standards make the cost shoot up?
(Dr Roberts) We do not really know the answer to that. All the evidence is that things like changes to fire protection and, perhaps, standards of lift and, perhaps, the robustness of structures might add a couple of per cent to the cost of the buildings, really quite small amounts to the construction costs. These are mostly issues of detail that if you put them in right at the beginning are quite easy but to retrofit them might be a different matter.

414. Is there a big problem in the area of non-compliance with the existence of evacuation?
(Dr Roberts) I would think non-compliance is very low in the United Kingdom with our building regulations, which control the physical construction and with the fire certificate system which controls the fire certification for the user. For both of those, particularly for large buildings, I think the compliance is extremely good in the United Kingdom.
(Mr Bressington) Where there is a slight change is if you look at active systems, sprinkler systems and detection systems, these are relatively easy to test and check and the installation of these systems are often part of the certification scheme, where someone looks at the system, they check it, they commission it, they give them a piece of paper to say that everything is okay and then they test it every so often. It is much more difficult when you talk about passive protection, it is much more difficult to control the quality of that because what happens often in a building over its life is it will be changed internally, people will take partitions down and there are going to be ceilings they will punch through. I think the way that is regulated probably does need looking at. In a tall building with lots of people in there we may need something a little bit more in terms of management to be able to do that.

415. What is the extent of the problem in that area, where the building may be meeting all the regulations and then it changes adaptations?
(Dr Roberts) In the United Kingdom building regulations are not retrospectively applied unless you change the use to certain key uses, which basically revolve round whether people are living or sleeping in the building. New building regulations do not apply retrospectively to existing buildings at the moment unless you have a change of use to a hotel or residential accommodation and then the fire requirements can be retrospectively applied. The issue of control of people removing fire partitions is a more serious issue. Although new buildings are really very well policed in the United Kingdom existing building amendments are probably not so well policed.

416. Has that been identified as an area for concern in your Committee?
(Dr Roberts) No, it has not at the moment because we are not really focussing quite so much on pure physical issues, it is a sort of combination of management issues as well as the physical side.

417. You have identified between you as an issue of concern in terms of safety?
(Mr Bressington) For certain it has been identified, amongst others, by the London Fire Brigade. They did a workshop and I gave a paper there and from the questions that people had and talking to people I think this whole issue about the lifetime of a building and the way that it is used and whether there should be an operator's licence so that you have to make sure all of these things are in place, so they can be picked up, perhaps it can be part of the fire certificate or whatever, it is the on-going on management of these buildings. These events are very rare, even a conventional fire. If the systems are not there to deal with it or people do not have the training to be able to deal with it that is where it will fall. It will not fall by the systems themselves. That is the key to all of this, particularly now if we are having to look at different evacuation regimes, it is not just phased evacuation now, we have to look at simultaneous evacuation or other situations where we may have to move people up from the ground floor if there is a bomb in a car outside, it gets more complicated. We need to have procedures in place where people can consider those, I think.
(Dr Roberts) The question of licensing people to occupy tall buildings generally is a vexed question because you do not have to do anything on an annual basis to continue to occupy major office buildings. That is in contrast to things like sports grounds, where you have to have an annual safety certificate. Close to my own heart, because I am not a tall building designer, but I "safety engineer" for the London Eye, you are probably aware that that has to have an annual safety certificate otherwise it cannot be used and yet we have buildings with thousands of people in them that do not have to have any renewal permit arrangements.

418. Who is the responsibility body?
(Dr Roberts) The employer is responsible through normal legislation to have safety certificates in place for the fire escapes but no management issues are tested out through any kind of authorisation.

419. Are you saying then that there is no official body who would automatically make checks in these areas?
(Mr Bressington) The Fire Service check and issue fire certificates. Obviously they are going to limit that, they have lots of things to do, to a view of what is there. In large or complicated buildings the management is the main issue and it is how you monitor the success of that. I know some time ago I went to Basildon Shopping Centre and met the guy who managed that and also the fireman. They were very happy about the way things worked there because what used to happen is they would put on a fire certificate for that centre, which was renewed every so often, certain requirements in terms of displays, so what they did between them was to develop this type of thing. They said, okay, the fire certificate is not just dependent upon a checklist or ticking a box.

420. Was this done by two individuals?
(Mr Bressington) This was a way they decided

421. There is no system where somebody or some authority is responsible. Would you say this is a gap?
(Mr Bressington) There is a gap, I think, yes.

Chairman

422. Are you saying we should have new regulations for all tall buildings or just those over 30 metres?
(Dr Roberts) I have not come to any conclusion, I am afraid. I know these things take some time. By the standards that apply we are committed to quite a quick response and are intending to publish a guidance document by the end of March, which is really quite quick.

423. Yes, it is. If we are dealing with the elements, if we can move on from fire to wind, the windy city, Chicago, is that name given to it because of its historic position or is it because it got so windy between the skyscrapers?
(Mr Allsop) By all accounts at one time they used to have an area round the goods yard which was completely covered in black smoke and it did not move round very much. In fact the wind climate of Chicago is probably a bit less windy than London. The problem in Chicago is that you have the lake and the wind comes straight across the lake and straight up against the tall buildings and they catch the wind like a big sail and deflect it down towards ground level and produce the winds that you find there.

424. The skyscrapers are to blame for it?
(Mr Allsop) The skyscrapers and the arrangement of the skyscrapers there are partly to blame for that, yes.

425. Is it relatively easy if you are putting up a new block to see what effect it is going to have on the micro climate?
(Mr Allsop) When we put up very large blocks it is treated very seriously indeed, they are usually wind tunnel tested to measure the wind speed up of the various directions. We have to take account of the shape of the building and the surroundings are very important as well to the wind that is created in the streets. We take account of the wind strength and how long it blows in various directions and work out the percentages of time that the wind exceeds certain criteria. On that basis you can get an assessment of how windy one place is compared with another. That is done pretty thoroughly for the taller buildings. The problem, as I see it, is not these buildings—they are checked out—but a lot of the wind problems you get are not necessarily associated with particularly tall buildings. 20 storey buildings are very wide and orientated the wrong way against the wind can create quite a wide area of poor wind conditions which are unusable for sitting out or anything like that, whereas a tall building with a narrow floor plate creates a much smaller wind. Since about the 1970s these techniques have been developed for evaluating the wind and, therefore, we have the tools to manage this. You are probably aware of places like Centre Point where they deliberately created an open square in front of it as part of the merits of having a 100 metre building. Those open spaces allow the wind down and in. That is something that the planning officers need to be aware of when they are asking for these areas of the quality you are going to achieve in those areas. We can quantify it but it is up to somebody else to decide what the merit is of a particular target for those spaces.

426. You can design a tall building and you can design a nice public space in front of it without it being too windy?
(Mr Allsop) The important thing is to be aware of the quality of space that you are creating and that it is appropriate. If you are looking for a quiet, calm park then what you need is nice Georgian, squared, low-rise buildings of equal height all the way round it if that is what you want. You cannot just arbitrarily pick a point and say, "I want this here, therefore I can have it", because it does not quite work like that, you sometimes have to work hard to achieve that.

427. You think a lot of extra tall buildings could put be into the City of London without making it a windy, unattractive street environment?
(Mr Allsop) It needs to be done carefully. The Chief Planner of the City of London has taken quite an interest in this. In other areas there is, perhaps, less interest taken in it. I would say the problem is not one specifically of tall buildings, even ground scrapers are going to create a bad environment if handled wrongly.

428. Lastly, this new generation of tower, is it going to have cutting edge technology, do we need to worry about that or ought it all to stand up? Sometimes when I am in a tall building and I see what appears to be a thin think piece of glass between me and the street below that gives me a feeling as to what would happen if the piece of glass fell out. Should I be worried?
(Dr Roberts) I do not think you should be worried in the structural sense. I worry, as you do, about the view, looking out through the glass, but that is a different matter altogether. I think that the evidence is that the designs for large and small buildings are good in the basic structural sense. I think the attention is to do with the management and use of the buildings which have large numbers of people in them rather than those sort of issues like is the glass too thin.

Chairman: On that note can I thank you very much for your very helpful evidence. Thank you very much indeed.