Detour Signs
Route and trailblazer signs that direct traffic around a closure along an approved detour path.
Detour signs guide road users around a closure and along an approved alternate route, then back to the original road. A complete detour is signed continuously — from the advance warning (DETOUR AHEAD), through every decision point with directional DETOUR markers, to an END DETOUR where traffic rejoins the route.
In California, the detour markers (M4-8, M4-9, M4-9a) use a fluorescent orange background with a black legend in the temporary traffic control context. When sidewalks or crosswalks are affected, a pedestrian detour (M4-9b) routes people on foot along an accessible alternate path.
The most common detour plan-review issue is a gap — a turn or decision point left unsigned, or a detour that never returns traffic to the original route. In Los Angeles, detours affecting transit may require coordination with LADOT and LA County Metro.
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All Detour Signs
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Warns drivers that a detour is ahead and that the normal route will be interrupted, prompting them to prepare to follow an alternate path.
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.
Official Sources (external)
This is an educational reference. Verify sign use, size, placement, and application against the current CA MUTCD, Caltrans sign specifications, Standard Plans, and the reviewing agency. Official source links are gathered in one place.
View official sourcesEducational 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.
Frequently Asked Questions
What makes a detour 'complete' on a TCP?
A complete detour is signed from the advance warning through every turn and decision point and includes an END DETOUR where traffic rejoins the original route. Reviewers look for continuity — no unsigned turns and a clear return to the route.
How is a pedestrian detour different from a vehicle detour?
A pedestrian detour (M4-9b) routes people on foot around closed sidewalks or crosswalks along an accessible path. It must maintain ADA-compliant access and is shown with R9-series sidewalk-closure signs and barricades.
What color are detour signs in a California work zone?
In the temporary traffic control context, detour route markers use a fluorescent orange background with a black legend and arrow, matching the surrounding work-zone signs.
Running a detour on a California project?
Public Ready can supply the full detour sign package — advance warning, directional markers, end detour, and pedestrian detour — and help you lay it out on the TCP.
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