Identifies an approved detour route, marking the path drivers should follow around a closure when used with directional arrows.
MUTCD-style sign reference illustration. Always verify against the official CA MUTCD and Caltrans sign charts.
| 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) |
Download this sign or open the official MUTCD reference.
Official source: FHWA Standard Highway Signs, 2024 (11th Edition) — Guide signs.
Source: FHWA Standard Highway Signs — Public Domain. California: CA MUTCD 2026 (effective Jan 18, 2026).
Files linked from FHWA are official government publications in the public domain. CA MUTCD and Caltrans links open official government websites. Always verify against the current edition.
Identifies an approved detour route, marking the path drivers should follow around a closure when used with directional arrows.
Identifies an approved detour route, marking the path drivers should follow around a closure when used with directional arrows. 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.
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 field deployments
Agency review note
StreetsLA, LA County DPW, and Caltrans District 7 may require larger sizes or additional devices. Verify with the reviewing agency before finalizing the TCP.
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.
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).
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.
Confirm the detour is signed continuously at every turn and rejoins the original route. Public Ready reviews detour route completeness.
These signs are typically deployed alongside M4-8 on a California TCP.
Marking a detour route? Public Ready can supply DETOUR (M4-8) and the directional arrow markers.
Free official resource — opens official government website
Free official resource — opens official government website
Free official resource — opens official government website
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.
To understand the bigger picture around permits, agency review, lane closures, and pedestrian access for work zones using M4-8 Detour, visit WorkZoneCompliance.com.
Public Ready can help with M4-8 Detour — including sign rental or purchase, work-zone signs, TCP sign legends, and permit coordination, and agency-review support for Caltrans District 7, the City of Los Angeles, and LA County.
