Have you ever looked at architectural illustrations, showing relaxed people happily interacting with their built environment, all distributed evenly across the landscape, and thought; that’s not how our buildings and cities actually look. The truth is that many buildings have one busy entrance/exit and another that is not used; cities have a crowded street next to an empty street, with both linking the same locations.
Until recently we designed our built environment with the best intentions and hoped they would be used as planned. We try to anticipate the behaviour of crowds and design to account for those characteristics, but we never know how people will interact with spaces until they are constructed and used. Crowd simulation software may have been around for more than 25 years and is often backed up by academic research and empirical observation, but we still design and hope.
However, a recent technology integration gives us unprecedented insight into the potential behavior of crowds, with huge implications for the design of buildings, cities and public spaces. Instead of running simulations, which involves importing and storing large amounts of environmental data, we can now tie 3D Building Information Modelling (BIM) models into advanced crowd simulation software. Considering the growing wealth of data that can be brought into BIM simulations, crowd flow in the built environment can now be more realistic and reliable than ever.
A piece of software called MassMotion is at the heart of this evolution. Developed by Erin Morrow and his team at Oasys Software, MassMotion’s algorithms go through the geometry to work out adjacencies of spaces and building features, and to map out the alternative routes available to agents. Essentially predicting what people would do when faced with the options and obstacles in a specific environment.
“These are 3D agent-based models. They are based on real spaces with continuously connected 3D geometry and crowd interactions. Agents have size and acceleration, personalities that prefer things like avoiding going up stairs. They can dynamically assesses their environment and make routing decisions. Social forces determine how agents respond to their environment, other people, and goals. They try very hard not to hit obstacles or bump other agents. Agents are able to make autonomous decisions based on this continuous space.
For example, MassMotion can simulate how agents will be behave when faced with a choice between a crowded elevator or empty stairs,” says Geoff Zeiss, Principal at consulting firm, Between the Poles.
The simulation was originally conceived in 2003 when Arup was designing the Fulton Center, a project in lower Manhattan, New York, which included a commercial center and a new station that connected six different subway lines. Faced with a design and no way to test it, Arup called on Morrow to help solve the problem and MassMotion was born.

In the subsequent years MassMotion continued to evolve, as did BIM, and their integration has produced what is now probably the most accurate way to design spaces for the flow of people. Oasys Software has even used the system to assess modern and historic buildings, in order to track our progress in designing spaces for crowds, and they have unearthed some surprising results.
“In truth, the Romans had the core concepts in hand. A few years ago, the MassMotion team ran a comparison of the Colosseum in Rome with the Beijing National Stadium – designs separated by 2000 years of culture and technology. They found that both stadia would take around 15 minutes to evacuate. In short, the Romans had cracked the basics, and indeed we still use much of their thinking today,” explains Lynne East, PR for Oasys Software.
With these new tools the future of buildings, cities and public spaces looks smooth and functional, potentially much like the architectural illustrations that we have learned not to believe. Current structures can apply the simulations to explore the best options for retrofitting to improve the flow of people. Whilst future evolutions of this technology partnership will no doubt allow us to build more complex structures than ever before. We will finally be able to plan spaces to suit people, instead of adapting people to suit spaces.
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