Fruin - levels of service

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Crowd density (people per square metre) and crowd flow (people per metre per minute) are relalated.

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Which converts to the following density versus flow diagram (animated below)

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Which is often illustrated as the diagram below.

Screen Shot 2012-01-15 at 21.06.05

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Queueing

Image3

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And can be illustrated using the following space metric (feet and metres)

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As density increased flow increases, but only until critical density is reached. This critical density can be different for different events/crowds. As density (people per square metre) increases above the critical density the crowd flow begins to drop. Crowd flow is also a function of the crowd order, armies marching can achieve a greater flow rate at higher densities than a mixed demographic crowd. 

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We illustrate the flow versus density graph using both a colour and a graphic to show the density. A number of documents and standards use area per person. This can be confusing and we recommend that you always use people per square metre - it's easier to visualise and it maintains a clarity for crowd safety. The colour scale is also indicative of risk. To highlight this we run classroom demonstrations using a simple piece of string (area 1 square metre) and ask delegates to measure the time for a group of people to walk 10m. It's an illustrative experiment - but it highlights the curve shown below.


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As density increased flow increases, but only until critical density is reached (2-3 people per square metre). This critical density can be different for different events/crowds. 

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As density (people per square metre) increases above the critical density the crowd flow rate begins to drop. Crowd flow is also a function of the crowd order. For example, armies marching in step can achieve a greater flow rate at higher densities than a mixed demographic crowd. In other words, order in the crowd can increase the flow rate as shown in the 3 axis graph below.

Screen Shot 2012-01-15 at 21.09.00


Click on the links below for a video clip of: 

2 people per square metre

3 people per square metre

4 people per square metre

5 people per square metre

5 people per square metre (marching in time)

6 people per square metre

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