M4 Series — Detour and Alternate Route Markers

The M4 Series provides the directional detour markers used to guide vehicles — and in some cases pedestrians — around a road closure along an approved alternate route. M4-8 (DETOUR) and M4-9 (DETOUR with a directional arrow) mark each turn along a vehicle detour. M4-9a is the bicyclist/pedestrian detour marker, and M4-9b provides a pedestrian-specific detour path for sidewalk and crosswalk closures. These signs use fluorescent orange backgrounds in California temporary traffic control contexts.