LEFT LANE MUST TURN LEFT Sign Requirements
This guide summarizes the MUTCD requirements and practical application guidance for the R3-7L LEFT LANE MUST TURN LEFT 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
Assigning a mandatory left turn to the left lane at an approach
Where It Applies
At the point where the regulation applies, per CA MUTCD Part 2B.
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 MUST TURN LEFT Sign Is Used
Requires all traffic in the left lane to turn left at the intersection. It is a word-message lane-use control sign that removes any doubt about the mandatory movement for that lane.
- Assigning a mandatory left turn to the left lane at an approach
- Reinforcing lane-use control where lane assignments change in a work zone
- Paired with pavement lane-use arrow markings
2. How and Where It Applies
In the field, R3-7L Left Lane Must Turn Left is typically positioned at the advance warning area, ahead of the work. Common deployments include assigning a mandatory left turn to the left lane at an approach; reinforcing lane-use control where lane assignments change in a work zone; paired with pavement lane-use arrow markings. 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 R3-7L at the point where the regulation applies, per CA MUTCD Part 2B.
- 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: 30" × 30"; 36" × 36" on multilane or higher-speed roadways.
- 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 in California per the CA MUTCD to require a left turn from the left lane at an intersection or work-zone approach. Confirm its size, retroreflective sheeting, placement, and spacing against the CA MUTCD 2026 and the reviewing agency before finalizing the traffic control plan.
Go to California Notes6. Common Field or Planning Mistakes
- Temporary regulatory control not warranted or conflicts with existing control.
- Reduced speed limit posted without proper speed-setting authorization.
- Wrong-way protection (DO NOT ENTER / WRONG WAY) missing at closed approaches.
- Sign size not appropriate for the facility.
Related Resources
View All R-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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