The standard specifies that exits should be located every in road tunnels. It also mandates signage, survivability requirements, clear walking‑surface dimensions, and emergency doors. In contrast, NFPA 130 (the rail transit standard) requires exits every 2,500 ft, reflecting the different risk profiles and egress speeds of road versus rail tunnels.
NFPA 502, Standard for Road Tunnels, Bridges, and Other Limited Access Highways, represents the culmination of decades of research, operational experience, and technical consensus regarding fire and life safety in transportation infrastructure. From its detailed ventilation requirements anchored by the critical velocity concept, to its comprehensive fire suppression, electrical system, and periodic testing provisions, the standard provides an essential framework for protecting lives and preserving critical infrastructure. The standard specifies that exits should be located