DETOUR Sign Requirements

1. When a DETOUR Sign Is Used

Identifies an approved detour route, marking the path drivers should follow around a closure when used with directional arrows.

• Marking the detour route around a closure
• Mounted with M4-9 directional arrows at decision points
• Used with W20-2 DETOUR AHEAD advance warning

2. How and Where It Applies

Identifies an approved detour route, marking the path drivers should follow around a closure when used with directional arrows. In the field, M4-8 Detour is typically positioned at the along the detour route at each decision point. Common deployments include marking the detour route around a closure; mounted with M4-9 directional arrows at decision points; used with W20-2 DETOUR AHEAD advance warning. 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

Along the detour route at each decision point.

• 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: 24" × 12" (route marker / plaque).

• 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 to mark a detour around a closed road or lane, mounted above or with directional arrow markers to guide each turn.

6. Common Field or Planning Mistakes

• Detour not signed continuously at every decision point.
• Arrow direction incorrect at a turn.
• Detour does not return traffic to the original route.
• Pedestrian detour not addressed where sidewalks are affected.