W20-5b Left Lane Closed Ahead Sign
Warns specifically that the left-hand travel lane is closed ahead so traffic in that lane can merge right in advance of the closure.
| Sign code | W20-5b |
|---|---|
| Federal code | W20-5b |
| Name | Left Lane Closed Ahead |
| Category | Warning Signs |
| Shape | Diamond |
| Color | Orange background, black legend |
| California status | Used in California per CA MUTCD |
| Typical CA minimum size | 48" × 48" on conventional roads; 60" × 60" on expressways and freeways |
What This Sign Means
Warns specifically that the left-hand travel lane is closed ahead so traffic in that lane can merge right in advance of the closure.
California Temporary Traffic Control Use
Used on California multilane roadways to direct a left-lane merge ahead of the taper, sequenced with advance warning and channelizing devices.
Common TCP Context
- Left-lane closures on multilane streets and highways
- Placed ahead of the merging taper
- Paired with arrow boards and channelizing devices
California Size Requirements
Typical minimum: 48" × 48" on conventional roads; 60" × 60" on expressways and freeways.
Sizes are CA MUTCD minimums and vary by roadway classification and speed. Verify against the CA MUTCD 2026 (CA MUTCD Part 6 (Temporary Traffic Control), Chapter 6F; warning-sign design in Part 2C), Caltrans sign specifications, and the reviewing agency.
Common Placement on a TCP
Where it sits: Advance warning area, ahead of the work.
CA MUTCD reference: CA MUTCD Part 6 (Temporary Traffic Control), Chapter 6F; warning-sign design in Part 2C.
Los Angeles Area Usage Notes
In Los Angeles, this sign must conform to CA MUTCD 2026. Work in City of LA right-of-way is reviewed by StreetsLA and the Bureau of Engineering (BOE); state highways in LA County are permitted and reviewed by Caltrans District 7; county roads are permitted by LA County DPW. Sizes, retroreflectivity, and placement must meet CA MUTCD minimums — local agencies may require larger signs based on roadway class, speed, pedestrian volume, and proximity to schools or transit.
Common Plan Review Comments
- 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.
Plan Review Notes
Verify the merge direction matches field geometry and median constraints. Public Ready confirms left-lane closure sequencing.
Signs Commonly Used Together
These signs are typically deployed alongside W20-5b on a California TCP.
Rent or Purchase This Sign
Need LEFT LANE CLOSED AHEAD (W20-5b)? Public Ready can supply the sign and matching lane-closure devices.
Official References
- California MUTCD (Caltrans)
Free official resource — opens official government website
- Federal MUTCD (FHWA)
Free official resource — opens official government website
- Caltrans Sign Charts
Free official resource — opens official government website
- FHWA Standard Highway Signs
Free official resource — opens official government website
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.
Related Signs
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