M4-8 Detour Sign
Identifies an approved detour route, marking the path drivers should follow around a closure when used with directional arrows.
| Sign code | M4-8 |
|---|---|
| Federal code | M4-8 |
| Name | Detour |
| Category | Detour Signs |
| Shape | Rectangle (Horizontal) |
| Color | Orange background, black legend (temporary traffic control use) |
| California status | Used in California per CA MUTCD |
| Typical CA minimum size | 24" × 12" (route marker / plaque) |
What This Sign Means
Identifies an approved detour route, marking the path drivers should follow around a closure when used with directional arrows.
California Temporary Traffic Control Use
Used in California to mark a detour around a closed road or lane, mounted above or with directional arrow markers to guide each turn.
Common TCP Context
- Marking the detour route around a closure
- Mounted with M4-9 directional arrows at decision points
- Used with W20-2 DETOUR AHEAD advance warning
California Size Requirements
Typical minimum: 24" × 12" (route marker / plaque).
Sizes are CA MUTCD minimums and vary by roadway classification and speed. Verify against the CA MUTCD 2026 (CA MUTCD Part 6, Chapter 6F, and Part 2D (Guide Signs)), Caltrans sign specifications, and the reviewing agency.
Common Placement on a TCP
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).
Los Angeles Area Usage Notes
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.
Plan Review Notes
Confirm the detour is signed continuously at every turn and rejoins the original route. Public Ready reviews detour route completeness.
Signs Commonly Used Together
These signs are typically deployed alongside M4-8 on a California TCP.
Rent or Purchase This Sign
Marking a detour route? Public Ready can supply DETOUR (M4-8) and the directional arrow markers.
Official References
- California MUTCD (Caltrans)
Free official resource — opens official government website
- Federal MUTCD (FHWA)
Free official resource — opens official government website
- Caltrans Sign Charts
Free official resource — opens official government website
- FHWA Standard Highway Signs
Free official resource — opens official government website
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.
Related Signs
Need signs for a California project?
Need to rent, purchase, or include traffic control signs on a California project? Public Ready can help with sign rental, purchase, sign packages, TCP sign legends, and permit coordination.