LEFT LANE CLOSED Sign Requirements
This guide summarizes the MUTCD requirements and practical application guidance for the W20-5L LEFT LANE CLOSED sign. Use this resource to understand when it is required, how to place it correctly, and how to maintain clear visibility for safe operations.
When It Is Used
Left-lane closures on multilane streets and highways
Where It Applies
Advance warning area, ahead of the work.
Placement Basics
Mount at the standard height and setback for the roadway with clear sight lines.
Visibility / Reflectivity
High reflectivity and clear sight lines are essential day and night.
1. When a LEFT LANE CLOSED Sign Is Used
Warns that the left-hand travel lane is closed ahead and that traffic in that lane must merge right before the work area. The distance legend may read AHEAD, a distance in feet, or a distance in miles.
- Left-lane closures on multilane streets and highways
- Placed in the advance warning area ahead of the merging taper
- Paired with W4-2L and channelizing devices or an arrow board
2. How and Where It Applies
In the field, W20-5L Left Lane Closed is typically positioned at the advance warning area, ahead of the work. Common deployments include left-lane closures on multilane streets and highways; placed in the advance warning area ahead of the merging taper; paired with W4-2L and channelizing devices or an arrow board. Always confirm its size, retroreflective sheeting, spacing, and placement against the CA MUTCD 2026 and the reviewing agency before finalizing the traffic control plan.
3. Placement and Application Notes
Position W20-5L advance warning area, ahead of the work.
- Place the sign where drivers have a clear, unobstructed view on approach.
- Mount at the standard height and setback from the edge of the traveled way.
- Do not mount with other signs on the same post unless space constraints require it.
4. Standard Sizes and Visibility Considerations
Typical minimum: 48" × 48" on conventional roads; 60" × 60" on expressways and freeways.
- Choose size based on roadway speed, sight distance, and mounting location.
- Maintain high retroreflectivity for maximum night and adverse-weather visibility.
5. California Notes
Used on California multilane roadways to warn of a left-lane closure ahead of the merging taper, sequenced with advance warning and channelizing devices. Choose the distance legend (AHEAD / XX FT / XX MILE(S)) to match the plan.
Go to California Notes6. Common Field or Planning Mistakes
- Merge direction on the sign does not match the open lane in the field.
- Taper begins before the lane-closure warning is reached.
- Sign spacing not adjusted for the posted speed.
- Wrong size specified for a multilane facility.
Related Resources
View All W-Series 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. Written against California MUTCD 2026 (effective January 18, 2026) and the Federal MUTCD 11th Edition. Official sources last verified June 2026.
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