M4-9L Detour (Left Arrow)
Combines the word DETOUR with a left-pointing arrow to direct drivers to turn left at this point of the detour route. Note: “M4-9L” is a directional label used on this site to identify the left-arrow version of the detour marker. FHWA does not issue M4-9L as a separate sign code — the official designation is M4-9 “Detour,” which is shown with either a left- or right-pointing arrow as the route requires.
- Sign Name
- Detour (Left Arrow)
- MUTCD Code
- M4-9L
- Sign Category
- Detour Signs
Specifications
- Shape
- Rectangle (Horizontal)
- Color / legend
- Orange background, black legend and arrow (temporary traffic control use)
Sizes & Dimensions (inches)
These are dimensions shown on the linked layout. Select the required size using the applicable MUTCD and agency requirements; the smallest drawing size is not necessarily the permitted minimum.
- Layout 130" × 24"
- Layout 248" × 36"
When & Where It's Used
- Left turns at detour decision points
- Used in sequence with M4-9 (right arrow) and M4-8 DETOUR markers
- Common on local-street detours around closures
Placement Context
- Where it sits
- At the detour decision point or route assembly identified by the design.
- CA MUTCD reference
- CA MUTCD 2026 Chapter 6I — TTC Zone Guide Signs (general context)
Related Signs
Browse Detour Signs
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. Reference editions: California MUTCD 2026 (effective January 18, 2026) and the Federal MUTCD 11th Edition with Revision 1.
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