Virtual polka dots predict spectator flows for Grand Départ

Simulations in virtual environment help city of Utrecht prepare for Grand Départ

Simulatie van het Utrechtse Jaarbeursplein
Virtual Grand Départ visitors at the Jaarbeursplein
Een virtuele menigte op het Domplein
A virtual crowd at the Dom square

The Grand Départ of the Tour de France is expected to draw anywhere from 600,000 to 800,000 spectators to Utrecht. Simulations in a virtual Utrecht support the municipal government in planning the surroundings of the cycling course and testing the prognoses for the flows of the spectators. These innovative simulations in an unprecedentedly detailed virtual world were the result of collaboration between computer scientists at Utrecht University and the engineering and consulting bureau Movares.

In the run-up to the Grand Départ, Movares utilised the virtual environment ‘Reach!’. This virtual environment automatically generates a 3D model based on the data provided by the city. Next, all of the organisational objects, such as stadium seating, crowd control fences, toilets and signs were entered and visualised for the first two stages of the Tour de France on 4 and 5 July. The integration with simulation software for the flows of people at Utrecht University also facilitated the visualisation of the behaviour of the flows of spectators. This helped the organisers of the Tour in Utrecht to test their existing ideas about the movement of spectators, while also allowing them to visualise various simple scenarios, such as the effect that an extra 50,000 spectators would have.

Faster and more realistic

For several years, the computer scientists in Utrecht have studied how to simulate the behaviour of flows of people as accurately as possible in large 3D environments. Their efforts have resulted in software that is faster and more realistic than other simulation software. For example, they have developed a unique combination of two existing models for simulating movements of large numbers of people. In one model, each person acts as an individual, while in the other each individual is part of the larger ‘flow’. This combination unites the benefits of both models, allowing for the simulation of large masses with high or low densities.

And yet the level of realism could be even higher, according to Dr. Roland Geraerts, Assistant Professor in the Virtual Worlds research group at Utrecht University and work package leader at COMMIT/*. The researchers will therefore compare camera images of the spectator flows during the Grand Départ to the simulations immediately afterwards in order to examine how the model can produce more accurate predictions. Geraerts also works on supplementing the model with realistic social behaviour of smaller groups of people who are out together, and who therefore try to stay in one another’s proximity.

Looking forward

The software developed by Geraerts and his colleagues is so advanced that it can simulate more than one million people on a single computer. This makes the simulations extremely fast, which in turn enables Geraerts to achieve his next ambition: to follow the flows of people during an event and to look forward a few minutes in the future to predict whether it may become too crowded at a specific location, so that measures can be taken to prevent dangerous situations.

However, Geraerts remains modest about the role of simulations. “The organisers already have a wealth of experience dealing with these types of big events. What we add is a tool that makes it easier for them to prepare an event with all of the parties involved.”

Movares and Utrecht University are partners of Le Tour Utrecht.

* This research was funded in part by COMMIT/. COMMIT/ brings together scientific research, non-profit organisations and commercial organisations in ICT projects within the most important economic sectors in the Netherlands in order to study and develop ground-breaking products and services. COMMIT/ unites more than 100 parties, universities and technology institutes together with 80 large and small businesses to work on projects that play a major role in the international stage. In so doing, COMMIT/ contributes to reinforcing the top sectors and helps maintain the Netherlands’ lead as a high-knowledge country. For more information, visit:

A scientific video presentation of Geraerts' crowd simulation algorithm