Lane Closed Sign (W20-5): What It Means

RIGHT LANE CLOSED AHEAD (W20-5). Illustration drawn by Safe Pass Traffic; not to scale.

The orange diamond that reads RIGHT LANE CLOSED or LEFT LANE CLOSED is the Lane Closed sign, W20-5. It tells you that one through lane of a multi-lane road is closed ahead, so you need to move out of that lane before you reach the closure. It is a warning, not a road closure: the road stays open in the remaining lanes.

What it means

Under Section 6H.07 of the California MUTCD 2026 Edition, a Lane Closed sign shall be used in advance of the point where one or more through lanes of a multi-lane roadway are closed. For a single lane closure the legend is RIGHT (LEFT) LANE CLOSED (W20-5). Where two or more adjacent lanes are closed, the W20-5a sign uses the legend XX RIGHT (LEFT) LANES CLOSED. The distance line may read XX FEET, XX MILES, or simply AHEAD.

California adds its own versions. The LANE(S) CLOSED sign C20(CA) may be used by itself or with a LEFT overlay (C20A(CA)) and/or a numeral overlay (C20B(CA)). The LANE CLOSED sign C30(CA) may be placed within the closed lane of a multilane highway as follow-up information after the advance warning signs, and it may be repeated at intervals through long closures as a reminder.

What drivers often get wrong

Waiting until the last moment to merge. The sign is placed in advance so you have time to change lanes smoothly. Follow any merge instructions posted for that closure.
Reading it as a road closure. LANE CLOSED means one or more lanes are out of service; the other lanes stay open. A white ROAD CLOSED sign is a different message entirely.
Assuming the closure is over after the taper. On long closures the C30(CA) sign may be repeated inside the closed lane as a reminder that it is still closed.
Confusing it with a lane shift. When work occupies an interior lane and traffic is shifted around it, the Interior Lane Shift sign (W9-3) is used instead of a simple right or left lane closed message.

Where it goes in a work zone

The Lane Closed sign sits in the advance warning area, ahead of the transition where the lane is tapered off. Section 6H.02 says advance warning sign spacing varies with road type, condition and speed. When a series of signs is used, the sign closest to the transition or activity area ranges from about 100 feet on low-speed urban streets to 1,000 feet or more on freeways and expressways. Where several advance warning signs are needed, ROAD WORK AHEAD (W20-1) should be the first one drivers see, with the lane closed message following it.

An arrow board often supplements the signs at the start of the taper. Per Section 6L.06, arrow or chevron mode shall be used only for stationary or moving lane closures on multi-lane roadways, which is exactly the situation this sign warns about.

What contractors need to know

Pick the right legend: W20-5 for a single lane, W20-5a when two or more adjacent lanes are closed, or the C20(CA) sign with overlays where the permitting agency prefers California signs.
For interior-lane work with a shifting taper, the W9-3 Interior Lane Shift sign should be used in advance. The CA MUTCD says not to use the CENTER LANE CLOSED AHEAD (W9-3) sign for moving lane closures on State highways; moving closures on State highways follow Caltrans Standard Plan T-16.
Sign spacing, taper lengths and device counts come from the manual’s tables and the agency’s standards, and the permitting agency may require its own details. Those belong on the traffic control plan.
The arrow board supplements the signs; it does not replace them.

Related signs

Frequently asked questions

What is the difference between W20-5 and W20-5a?

W20-5 is for a single closed lane (RIGHT or LEFT LANE CLOSED). W20-5a is used where two or more adjacent lanes are closed and reads XX RIGHT (LEFT) LANES CLOSED.

What is the C30(CA) LANE CLOSED sign for?

It is a California sign that may be placed within the closed lane of a multilane highway as follow-up to the advance warning signs, and it may be repeated through long closures as a reminder.

Does a lane closure need an arrow board?

Not always; the manual and the permitting agency set when one is needed. When one is used for a lane closure on a multi-lane road, it runs in arrow or chevron mode.

Sources

Need this sign on a traffic control plan?

Safe Pass Traffic prepares PE & TE stamped traffic control plans, striping plans and typical plans for projects statewide in California, and helps with the permit submittal. We draw the plan that shows which signs go where; your contractor or traffic control provider sets them in the field. Call or text (714) 362-1348 or request a quote.