Every person is a body with a radius, a mass and a preferred speed. Each step they feel a pull towards their chosen exit, a short-range push away from people and walls, and, once bodies touch, contact and sliding friction. This is the social-force model of Helbing, Farkas & Vicsek, so arches, clogging and crowd pressure emerge on their own; they are not scripted.
Routes come from a fast-marching distance field for every exit, so people walk around furniture and through doors instead of in straight lines. Every half second they may switch exits, weighing walking time against the queue ahead. Exit knowledge moves them from pure habit (the way they came in, never the fire exits) to fully informed.
Where it jams: the Congestion layer lights up where the crowd is dense and barely moving. Rings mark live jams, named after the choke point at the head of each queue. The Jam map adds up the person-seconds lost at every spot over the whole run, and the report ranks the worst ones.
Ideas to try: close the busiest exit; add a second door to the bottleneck; drop a pillar in front of a door; crank urgency to panic and watch the pressure layer.