Circulation diagrams are the architect's tool for making invisible movement patterns visible. They translate the complex web of people moving through a building into clear graphic representations that drive programming decisions and prove code compliance.

On the PA exam, you won't just be asked what a circulation diagram shows. You'll be expected to analyze one. That means evaluating whether a diagram correctly represents horizontal movement along corridors and through connected spaces, vertical movement through stairs, elevators, and escalators, and egress paths that satisfy code-mandated travel distances and exit separations.

Three distinct diagram types show up repeatedly. Horizontal flow diagrams map movement across a single floor: public versus private zones, primary versus secondary corridors, and the way people actually move from entry to destination. Vertical movement diagrams address stairs, elevators, ramps, and shafts, showing how floors connect and where vertical cores concentrate. Egress diagrams overlay code requirements onto both, marking travel distances, dead-end limits, exit separations, and required exit widths.

These diagrams aren't decorative. They're decision-making tools that shape space adjacencies, corridor widths, core placement, and ultimately the entire building program. The PA division tests your ability to look at one of these graphics and determine whether the relationships it communicates are appropriate for the program requirements.