Hi. I'm working on a project which involves estimating crowd flow. I'm not the fire officer but would like to be able to understand the numbers involved. A friend of mine who works in Health and Safety suggested that I should post my problem here. All assistance hugely appreciated, because I'm a complete layman when it comes to this stuff. The project involves an egress route from a building with a very large crowd capacity. The route has an effective width of 12.5m which, according the crowd flow calculations (Effective width * 109 * 8 minutes) adds up to an exit route capacity of 10,900 persons. That part I understand. This is where I start to get lost. The end of the exit route widens to a width of 15.5m, which should increase the rate of crowd flow. However, there are two large metal barriers, each 2.5m in width, placed in that 15m space. To demonstrate: |---1.5m---BARRIER------------7.5m--------------BARRIER---1.5m---| As stated, each barrier measures 2.5m in width. The gap between the barriers measures 7.5m. The gap between the barriers to the outside wall on each side is 1.5m. Since 1.5m is only enough space to accommodate two unit widths (.55m), then am I also correct in stating that the effective width is only 1.1m? Using the same crowd flow calculations: - taking 7.5m+1.5m+1.5m as the "effective route width" (10.5*109*8) = 9156 persons - taking 7.5m+1.1m+1.1m as the "effective route width" (9.7*109*8) = 8458.4 persons - taking 7.5m as the "effective route width" (7.5*109*8) = 6540 persons In any of the above scenarios, the route simply cannot handle 10,900 persons. So, as somebody who is inexperienced in this field, can anybody tell me what I'm missing? And, if I'm actually correct in principle, how would one even begin to calculate the effect of the smaller exit width on crowd backlog? p.s. sorry for the terrible formatting - don't know how to lay it out nicely

Thanks very much for your reply. Just so I've got this right, you're saying that although some people would indeed go through the outside channels, the bottleneck created by the barriers would cause the crowd as a whole would bunch. Based on the lower side of your range for a crowd of 10900 to pass through, i.e. 14 minutes (t+50%), is it possible to estimate how many people such an exit route could handle in 8 minutes?

Yes. This 8 minutes limit is a requirement and is not a variable.

greenlake, In the design and situation under consideration, Using BS EN 13200 and the Green Guide. I would reduce design flowrate to 1.37 persons per metre per second and thereafter, it may be prudent to look at this as a simple mass balance: Exit with into area at 12.5 metres gives 1027.5 people entering per minute or (8220 people over 8 minutes). Exit through 10.5 metre exit gives 863.1 people leaving per minute or (6904.8 people over 8 minutes). People remaining is 164.4 per minute or (1315.2 over the 8 minutes). I am sure that you can carry out a similar mass balance based on 10,900 people entering the area. I believe that the design flow of 1.82 persons per second should not have been applied to either of the exits in question but regardless, I would look at the risk to people leaving the stadium upstream of the 12.5 metre exit from the products of fire. It is important to consider, did the design provide engineering control of smoke etc?

bleve, many thanks for your informative replies. They are of huge assistance.

Bob I could be very disingenuous but I will resist. By your own admission you do not have a clue as to what you are on about so why post? In addition, some of us namely me are experts on this field. As regards the building in question, I am intimately aware if the design and construction of same. Lastly, the post was put forward by an investigative journalist looking at the evacuation and crowd safety aspect of the design and modifications to the structure. My own opinion is that your response does little to present iosh in a good light. I would suggest that unlessyou know what you are talking about, that you refrain from demonstating your lack of knowledge