Graphic - Levels of Service
(updated 12th November 2008)
Keywords: Pedestrian Evacuation, simulations, simulating crowds, simulating behaviour, simulating people
Fruin Levels of Service
The Fruin Levels of Service is an important concept in the design of places of public assembly. One problem that keeps arising in workshops and training courses is applying the Fruin Levels of Service to metric scales. As Fruin relates to feet per minute and area per person we need to convert this to a metric scale for European applications.
First we need to define the body ellipse (see diagram below)
These dimensions are based on the following data.
Converting from feet (Fruin) to Metres (European) we derive the following table
In the Level of Service concept flow rate is expressed as a function of density. As the density increases the flow rate increases, reaches a Maximum THEN drops again. Area per person for Level of Service A indicates above as greater than 3.24 square metres per person. However this causes a little confusion - the table below shows the conversion by using colours to indicate the appropriate Level of Service.
We display this as an area graph to highlight the Levels of Service as a square area
By taking an area of 3 metres long and 1 metre wide we can display the above as a series of graphics (see below).
Level of Service A. Flow rate less than 23 people per metre per minute. Virtually unrestricted choice of speed; minimum manoeuvring to pass; crossing & reverse movements are unrestricted.
Level of Service B. Flow rate 23 to 33 people per metre per minute. Normal walking speeds only occasionally restricted; some occasional interference in passing; crossing & reverse movements are possible with occasional conflict.
Level of Service C. Flow rate 33 to 49 people per metre per minute. Walking speeds are partially restricted; passing is restricted but possible with manoeuvring; crossing and reverse movements are restricted and require significant manoeuvring to avoid conflict, flow is reasonably fluid.
Level of Service D. Flow rate 49 to 66 people per metre per minute. Walking speeds are restricted and reduced, passing is rarely possible without conflict; crossing and reverse movements are severely restricted with multiple conflicts; some probability of momentary flow stoppages when critical densities might be intermittently reached.
Level of Service E. Flow rate 66 to 82 people per metre per minute. Walking speeds are restricted and occasionally reduced to shuffling; frequent adjustment of gait is required and passing is impossible without conflict; crossing and reverse movements are severely restricted with unavoidable conflicts; flow achieves maximum capacity under pressure, but with frequent stoppages and interruptions of flow.
Level of Service F. Flow rate variable. Walking speed is reduced to shuffling; passing is impossible, crossing and reverse movements are impossible; physical contact is frequent and unavoidable; flow is sporadic and on the verge of complete breakdown and stoppage.
Modelling work at the Jamarah Pillars
Your should note that various crowd demographics can skew the above - such as the number of elderly or mobility impaired present in the crowd
The diagram (above) shows the profile that this density represents (data source - "Bodyspace - Anthropometry, Ergonomics and the Design of Work", Pheasant, Second Edition, ISBN 0-7484-0326-4).
To create crowd models we manipulate a 30cm square allow us to generate dangerous packing capacities (greater then 9 people per square metre).
1 person per square metre
2 people per square metre
3 people per square metre
3.5 people per square metre
4 people per square metre
8 people per square metre
8.4 people per square metre - note there is still space to accommodate up to 10 people per square metre but the risk to the crowd is severe.