Visitor flows (3D)
About this app
3D exhibition floor plan with visitors following the social force model: a tour with a highlight, a bottleneck with a door and counterflow, and the evacuation of a hall through one exit. The floor shows density in Fruin levels; a fundamental diagram compares measured speed and flow with the Weidmann curve. The list of evacuations shows that pushing creates arches in front of the door and lengthens the evacuation.
How crowds move
The social force model by Helbing, Farkas and Vicsek treats pedestrians as particles with intentions: each person heads for a goal at their desired speed and is pushed away by other people and by walls. On contact, body force and friction act. This produces effects known from real crowds: jams at bottlenecks, lanes in counterflow and arches in front of a door. How crowded it gets is described by Fruin’s levels from A (free) to F (packed), measured in people per square metre.
What the app shows
An exhibition floor plan in 3D with three scenarios: a tour through three rooms with six exhibits and a highlight in the middle, a corridor with a door and optional counterflow, and the evacuation of a hall with 50 to 400 people through one exit. The floor is coloured by density in Fruin levels, and figures under body pressure change colour. Readouts show density, flow per metre of width and evacuation time. A fundamental diagram compares measured speed and flow with Weidmann’s curve.
What you can try
On the tour, raise the inflow or the dwell time at the highlight and watch where density builds up. Narrow the door to 0.8 m or add counterflow. For the evacuation you set exit width, number of people and desired speed: in the model 200 people clear a hall with a 1 m exit in about 205 s when walking calmly, fastest at around 2.5 m/s; push harder and the exit jams. A column in front of the exit helps under high pressure. A teaching model, not a safety assessment.
Frequently asked questions
- What is the social force model?
- The social force model by Dirk Helbing and colleagues describes each person as a body acted on by virtual forces: a driving force towards the goal at the desired speed and repulsive forces from other people and walls. On body contact, pressure and friction forces are added. The model reproduces typical effects such as lane formation, jams at bottlenecks and arching at exits and is used in planning buildings and events.
- Why does an evacuation take longer when everyone pushes?
- The effect is called “faster is slower”. When everyone pushes towards the exit at once, bodies in front of it press together into arches that brace against the door frame and block the flow for a while. Nobody gets through until an arch breaks. Calm, brisk walking therefore often gives a higher flow than pushing. An obstacle such as a column just before the exit can split the pressure and weaken the arches.
- What are Fruin’s levels of service?
- John Fruin divided pedestrian densities into six levels, similar to levels of service in road traffic. In the app: A below 0.31 people per m², B up to 0.43, C up to 0.72, D up to 1.08, E up to 2.17 and F above. At levels A and B you can walk freely and overtake, from E movement is strongly restricted, and at F there is body contact and standstill.
- What can I try in the visitor flow app?
- You choose tour, bottleneck or evacuation and set inflow, dwell time at the highlight, door width, counterflow, exit width, number of people and desired speed; optionally a column stands in front of the exit. The app shows density on the floor, flow per metre, evacuation time and a fundamental diagram. A list compares your evacuations.
Subject: Architecture & scenography
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