Egress is a shortest-path problem.
Who This Matters To (And Why)
Critical: Architect,GC,City. These parties make or lose money directly based on this thesis.
Important: Engineer,Developer,Inspector. These parties execute decisions shaped by this thesis.
Context: Banker,Interior Design,Investor. These parties need to understand it to avoid friction.
Highest typology impact: Multifamily,Office,Hotel,Industrial. Lower impact: Retail,Mixed Use.
Egress is a shortest-path problem through the building graph. Code sets the maximum path length.
How It Shapes Development
Egress is a shortest-path problem because the building code question — can every occupant reach an exit within the allowed travel distance? — is a graph traversal problem. The floor plan is a graph. Rooms are nodes. Doors and corridors are edges. Exits are destination nodes. Travel distance is edge weight. Code compliance is verified by confirming that for every occupied node, there exists a path to an exit node whose cumulative edge weight does not exceed the code maximum. This is Dijkstra's algorithm applied to life safety.
IBC travel distance limits are 200 feet for sprinklered buildings and 75 feet for unsprinklered in most occupancy types. These limits define the maximum edge weight sum from any occupied room to an exit. A floor plan that routes occupants through long corridors, around elevator cores, and past dead ends will fail the travel distance check even if exits exist. The exits must be reachable, not just present. Floor plan layout is constrained by the shortest-path requirement: corridors must be arranged so that no point in the building is more than 200 feet from an exit along a code-compliant path.
Exit remoteness is a second graph constraint layered on top of travel distance. Exits must be remote from each other — separated by at least one-third of the maximum diagonal of the floor. This requirement ensures that if one exit is blocked by fire, an alternative path exists. It is a redundancy requirement on the graph: the graph must have at least two paths to exit nodes, and those paths must diverge sufficiently early that a single failure cannot block both. A floor plan with two exits stacked adjacent to each other satisfies the exit count requirement but fails the remoteness requirement.
Common path of egress travel is the most frequently violated egress provision. It measures the distance an occupant must travel before reaching a point where two directions of egress are available. IBC limits common path to 75 feet in most occupancies. A floor plan where a long dead-end corridor feeds into a single main corridor violates common path even if travel distance to exit is within limits. The graph interpretation is clear: common path measures the length of the initial segment before the graph branches. Too long a pre-branch segment means a fire at any point in that segment blocks all egress options simultaneously.