W5-3a ONE LANE UNDERPASS Requirements
Application notes for W5-3a ONE LANE UNDERPASS. The official manual distinguishes mandatory standards, recommended guidance, and optional applications; consult the linked sources for the provisions that apply.
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.
1. When ONE LANE UNDERPASS Is Used
Warns that an underpass is effectively restricted to one lane for two-way traffic.
- Roadway geometry and traffic-control review
2. Placement and Application Notes
Position W5-3a select placement using the actual approach, sight distance, applicable California manual provisions, and responsible agency requirements..
- Place the sign where the intended road users have a clear, unobstructed view on approach.
- Use the mounting height and lateral placement specified for the sign and installation type.
- Use sign assemblies and supplemental plaques only as provided in the applicable manual and approved design.
3. Layout Sizes and Visibility Considerations
Linked-layout dimensions: 30" × 30"; 36" × 36"; 48" × 48". Check the applicable MUTCD and agency requirements for the required installation size.
- Choose size based on roadway speed, sight distance, and mounting location.
- Use the visibility and material requirements specified for this sign and installation.
4. Sign Selection Checks
- Match W5-3a to the actual approach and traffic condition.
- 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.
- Select application size and installation using the California manual and agency requirements.
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Verify W5-3a Requirements
This is an educational reference. Verify sign use, size, placement, and application against the current CA MUTCD, Caltrans sign specifications, Standard Plans, and the reviewing agency. Official source links are gathered in one place.
View official sourcesEducational 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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