M4 Series — Detour and Alternate Route Markers
Detour Signs · CA MUTCD Part 6, Chapter 6H
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 with arrow) marks each turn along a vehicle detour. M4-9 and M4-9a are advance detour markers with distance information. 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.
California Field Use Notes
M4 signs must be placed at every decision point along the detour — each turn, merge, and return to the original route. A detour with any unsigned turn will fail plan review. In Los Angeles, detours affecting Metro bus routes or transit stops may require LADOT coordination. The pedestrian detour (M4-9b) must provide an ADA-accessible path with accessible ramps, crossings, and surface conditions.
Showing 9 of 9 signs
Identifies an approved detour route, marking the path drivers should follow around a closure when used with directional arrows.
Combines the word DETOUR with a directional arrow to point drivers toward the correct turn along the detour route.
Marks the end of a detour route, telling drivers they have returned to the original road and the detour is complete.
Directs pedestrians along an alternate accessible route when a sidewalk or crosswalk on their normal path is closed.
The California application of the pedestrian detour marker, used to route pedestrians around sidewalk and crosswalk closures along an accessible alternate path.
The M4-8a End Detour sign is a California MUTCD detour sign. It is shown here as an educational reference with the official FHWA Standard Highway Signs layout and California sizing guidance.
The M4-8P Detour sign is a California MUTCD detour sign. It is shown here as an educational reference with the official FHWA Standard Highway Signs layout and California sizing guidance.
The M4-9c Bicyclist Detour (with arrow) sign is a California MUTCD detour sign. It is shown here as an educational reference with the official FHWA Standard Highway Signs layout and California sizing guidance.
The M4-10 Detour sign is a California MUTCD detour sign. It is shown here as an educational reference with the official FHWA Standard Highway Signs layout and California sizing guidance.
Educational reference only. This is not an official Caltrans, FHWA, or local agency publication and is not legal or engineering advice. Always verify sign selection, size, placement, spacing, and application against the current CA MUTCD 2026, Caltrans sign specifications, Standard Plans, project documents, and the reviewing agency’s requirements.
Need M4 Series signs for a California project?
Public Ready can help you source, rent, or purchase M4 Series signs and integrate them into a compliant traffic control plan. For work zone compliance support, visit WorkZoneCompliance.com.