Circulation is the circulatory system of a building. Get it wrong and nothing else works, no matter how well the individual spaces are programmed. During the PA phase, you aren't detailing stair treads or specifying elevator cabs. You're making the big-picture decisions: how people, materials, and services move through the building, which routes need separation, and how much floor area circulation will consume.

Circulation typically accounts for 25% to 40% of a building's gross floor area, depending on building type and complexity. A simple office building might dedicate 25% to corridors, lobbies, and stairs. A hospital can exceed 40% because it requires separate clean, soiled, public, and staff pathways. That percentage directly drives the net-to-gross ratio, which determines whether the program fits the budget.

The ARE tests your ability to evaluate both horizontal circulation (corridors, entries, lobbies, loading docks) and vertical circulation (stairs, elevators, escalators, shafts, atriums). You need to assess how these elements connect programmed spaces, satisfy code-required egress, meet accessibility standards, and accommodate the movement patterns the program demands. For Objective 4.4, expect scenarios asking you to analyze circulation routes against program adjacencies, evaluate whether a proposed layout supports the required separation of user groups, or judge whether vertical connections are positioned to serve the functional relationships the program defines.