M4-8 Detour
Identifies an approved detour route, marking the path drivers should follow around a closure when used with directional arrows.
- Sign Name
- Detour
- General Meaning
- Identifies an approved detour route, marking the path drivers should follow around a closure when used with directional arrows.
- MUTCD Code
- M4-8
- Typical Use
- Along the detour route at each decision point.
- Sign Category
- Detour Signs
Specifications
- Standard Shape
- Rectangle (Horizontal)
- Background Color
- Orange
- Legend / Symbol
- Black legend
- Border
- Black
- Reflectivity
- High Intensity (for nighttime visibility)
- Compliance
- MUTCD / CA MUTCD
Standard Sizes (inches)
- Conventional Rectangle (Horizontal)24"–48" tall
- Expressway Rectangle (Horizontal)36"–60" tall
- Freeway Rectangle (Horizontal)48"–72" tall
Material / Application Notes
Marking the detour route around a closure. Confirm placement and supplemental plaques against the applicable CA MUTCD standard.
View this sign on the Federal MUTCD (FHWA)California Notes
California-specific application notes and adoptions may differ. Review California requirements where applicable.
What It Means / When This Sign Is Used
In the field, M4-8 Detour is typically positioned at the along the detour route at each decision point. Common deployments include marking the detour route around a closure; mounted with M4-9 directional arrows at decision points; used with W20-2 DETOUR AHEAD advance warning. Always confirm its size, retroreflective sheeting, spacing, and placement against the CA MUTCD 2026 and the reviewing agency before finalizing the traffic control plan.
Learn more about Detour sign requirementsWhen & Where It's Used
- Marking the detour route around a closure
- Mounted with M4-9 directional arrows at decision points
- Used with W20-2 DETOUR AHEAD advance warning
Placement on a Traffic Control Plan
- Where it sits
- Along the detour route at each decision point.
- CA MUTCD reference
- CA MUTCD Part 6, Chapter 6F, and Part 2D (Guide Signs)
- Typical minimum size
- 24" × 12" (route marker / plaque)
California / Field Use Notes
Used in California to mark a detour around a closed road or lane, mounted above or with directional arrow markers to guide each turn.
In Los Angeles, this sign must conform to CA MUTCD 2026. Work in City of LA right-of-way is reviewed by StreetsLA and the Bureau of Engineering (BOE); state highways in LA County are permitted and reviewed by Caltrans District 7; county roads are permitted by LA County DPW. Sizes, retroreflectivity, and placement must meet CA MUTCD minimums — local agencies may require larger signs based on roadway class, speed, pedestrian volume, and proximity to schools or transit.
Common Plan Review Comments
- Detour not signed continuously at every decision point.
- Arrow direction incorrect at a turn.
- Detour does not return traffic to the original route.
- Pedestrian detour not addressed where sidewalks are affected.
Confirm the detour is signed continuously at every turn and rejoins the original route. Public Ready reviews detour route completeness.
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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. Local jurisdictions may impose additional requirements, and final selection, placement, and dimensions may require engineering judgment or agency approval. Written against California MUTCD 2026 (effective January 18, 2026) and the Federal MUTCD 11th Edition. Official sources last verified June 2026.
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