This guide summarizes the MUTCD requirements and practical application guidance for the W3-4 BE PREPARED TO STOP sign. Use this resource to understand when it is required, how to place it correctly, and how to maintain clear visibility for safe operations.
Ahead of flagging stations and one-lane control
Advance warning area, ahead of the work.
Mount at the standard height and setback for the roadway with clear sight lines.
High reflectivity and clear sight lines are essential day and night.
Warns drivers that they may have to stop ahead, giving advance notice of a flagging station, queue, or signal that can require stopping.
Warns drivers that they may have to stop ahead, giving advance notice of a flagging station, queue, or signal that can require stopping. In the field, W3-4 Be Prepared To Stop is typically positioned at the advance warning area, ahead of the work. Common deployments include ahead of flagging stations and one-lane control; ahead of temporary traffic signals and queues; paired with W20-7 Flagger in the warning sequence. Always confirm its size, retroreflective sheeting, spacing, and placement against the CA MUTCD 2026 and the reviewing agency before finalizing the traffic control plan.
Advance warning area, ahead of the work.
Typical minimum: 48" × 48" on conventional roads; 60" × 60" on expressways and freeways.
In California work zones the orange (temporary) version follows the Flagger sign or precedes a temporary signal, alerting drivers before they reach a stopping point.
Go to California NotesEducational 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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