W5-3a One Lane Underpass
Warns that an underpass is effectively restricted to one lane for two-way traffic.
- Sign Name
- One Lane Underpass
- MUTCD Code
- W5-3a
- Sign Category
- Warning Signs
Specifications
- Shape
- Diamond
- Color / legend
- Black legend and border on yellow background
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.
Dimensions verified against the official drawing. Diamond dimensions are nominal side lengths. Select the required application size from the California manual; drawing sizes alone do not establish a permitted minimum.
- Official drawing size30" × 30"
- Official drawing size36" × 36"
- Official drawing size48" × 48"
California Application & Variants
Use the underpass design when the clearance, commercial-vehicle, or sight-distance criteria in California section 2C.19 apply. Determine whether STOP or YIELD control and additional delineation are needed.
When & Where It's Used
- Roadway geometry and traffic-control review
Placement Context
- Where it sits
- Select placement using the actual approach, sight distance, applicable California manual provisions, and responsible agency requirements..
- CA MUTCD reference
- CA MUTCD 2026 §2C.19
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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. Reference editions: California MUTCD 2026 (effective January 18, 2026) and the Federal MUTCD 11th Edition with Revision 1.
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