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Large crowds and Zone Ex: safety and security considerations in the last mile

September 23, 2019

Dr Aoife Hunt presented to the SGSA conference on 4th September on crowd movement research carried out at Wembley Stadium and also some of the latest security considerations, including the impact of Hostile Vehicle Mitigation (HVM), both with respect to Zone Ex. The presentation is summarised here.

Guide to Safety at Sports Grounds, 6th Edition
Guide to Safety at Sports Grounds, 6th Edition

The new (Green) Guide to Safety at Sports Grounds

For the first time, we are being formally asked to plan for “Zone Ex” outlined in the new Guide. This is not a new idea: “Last Mile” and “Grey Space” have been referred to in crowd planning for years, and many sports clubs and events already manage the spectator journey to and from local transport hubs and nearby attractions. However, the introduction of a formal accountability for crowd safety outside the sports ground has increased the attention given to planning for large crowds outside the venue.

Magic numbers

When we are designing for large crowds, planners look for“magic numbers”: benchmark figures we can hang our hats on. The most famous magic number is 8 minutes, which is considered to be the safe evacuation time for stadiums in the UK. It is paired with a magic exit flow rate (82 people per metre per minute): the British Standard rate to be used to calculate the number of people leaving a viewing area*. These benchmarks have been used across the world, and experience shows that setting capacity using these figures helps to create a safe stadium.

*This figure is 66 people per metre per minute if the exit is from a stepped surface.

We see the use of this flow rate in Zone Ex, even though crowd conditions are different inside and outside a stadium. It is important to consider where this magic number came from.

Scicon report

Where is 82 from?

The Scicon report, which assessed 15 different events across 11 sports grounds between October and December 1971, found a maximum flow rate of 25 people per feet per minute (around 82 people per metre per minute).  Although the authors of the Scicon report clearly stated:

‘We must stress that our figures are only based on a limited number of valid observations which could be made within the time limits of the study. Until the results are corroborated by further measurements they should be used with caution.’

… these figures are still used as the standard in the UK and in Europe, nearly 50 years on.

Stadum design, Movement Strategies

What does this mean for planning?

If we use the same flow rate throughout a site, it can lead to optimistic results as it doesn’t account for the larger numbers of people gathering outside a stadium than in the stadium and the different spaces available. Imagine it as a waterway, with streams leaving the relatively narrow confines of a stadium and joining together to make a larger river. If the whole system is travelling at the same rate, then it would flow easily and quickly, without obstruction.

The problem is, people don’t behave like water. People do not automatically and evenly use all the space available – especially as routes get wider. While a rate of 82 may work on exits from a viewing area, when there are large crowds in Zone Ex and different physical and social factors are present, the flow will likely be different and will almost certainly be lower.

Wembley research study, Movement Strategies

Wembley research study

To help address this issue, we partnered with leading authorities and expertise in the area of crowd dynamics. Two students from Lund University undertook the research for their MSc theses. Footage from recent surveys conducted by Movement Strategies of crowd flows exiting different sports and concert events at Wembley Park during 2017/2018 formed the basis for their research project.

Movement Strategies visitor profiles at concerts and football.

Key findings

This research investigated the impact of the crowd’s composition and walking conditions (e.g. density) on flow rates in four events: football, rugby league, and concerts starring Ed Sheeran and Taylor Swift. These events were selected to represent a varied set of people and social conditions.

The flow rates achieved were different across the events because of the behaviours of each type of crowd, and the size of individuals. For example, there were a large proportion of children and young adults in the Taylor Swift crowd, with smaller body sizes in comparison to the football crowd. This means that the Taylor Swift crowd had higher flow rates because they had more space to manoeuvre compared to the same number of football fans using the same space.

Full results on the difference between the events and crowds will be available next year (the research article is currently in review for publication).

This research investigated the impact of the crowd’s composition and walking conditions (e.g. density) on flow rates in four events: football, rugby league, and concerts starring Ed Sheeran and Taylor Swift. These events were selected to represent a varied set of people and social conditions.

The flow rates achieved were different across the events because of the behaviours of each type of crowd, and the size of individuals. For example, there were a large proportion of children and young adults in the Taylor Swift crowd, with smaller body sizes in comparison to the football crowd. This means that the Taylor Swift crowd had higher flow rates because they had more space to manoeuvre compared to the same number of football fans using the same space.

Movement Strategies, Flow rates and density

Full results on the difference between the events and crowds will be available next year (the research article is currently in review for publication).

Conclusions

This work shows that in Zone Ex flow rates are likely to be significantly lower than the rate of 82 people per metre per minute which is most often used for planning.

The standard rates should always be used for setting capacity inside sports grounds, but planners should use lower and more realistic rates to plan crowd movement outside of stadiums and in Zone Ex. For example, the use of crowd flow rates that are too high in Zone Ex may lead to evacuation plans that are too optimistic.

Next steps for research

We are continuing this research into large crowd movement, including new studies on crowds using stepped surfaces.

This year, we also be researching the impact of Hostile Vehicle Mitigation (HVM) on large crowds. These security measures are increasingly required to protect our crowds, given threat levels in the UK and elsewhere.

Current guidance has focussed on the use of bollards outside stations but has not yet considered the super-sized crowds we must protect at stadiums and events.

We are already working with stadiums in the UK to help security teams design their HVM to minimise the impact on crowd flows, while keeping their venue secure and are now collaborating with leading institutions and guidance providers to run an ambitious research study this year. The goal is to provide evidence and guidance to help sports grounds plan their HVM and crowd management strategies.

Testing HVM, Movement Strategies

The testing will be done in 2019/2020. Stadiums from around the UK have volunteered their sites by allowing our research team to come and monitor crowd movement before and after HVM is installed.

Please get in touch if your stadium or venue would like to be part of this research study.

If you are interested in finding out more about this work, or would like to get involved, please contact Dr Aoife Hunt.

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