What Is a Detour?

Why It Matters

A well-signed detour keeps traffic moving predictably around a full closure. Without clear guidance, drivers make unplanned turns and search for their own way around, which creates conflicts.

Detours also affect the surrounding street network, so the route is planned to handle the traffic it will carry and to return drivers to their original road.

Where It Shows Up in the Field

Detours show up where a road segment is fully closed for construction, an event, or emergency work. In Southern California, detours often route traffic through a grid of city streets and may cross more than one jurisdiction.

In the field, the detour is signed continuously so drivers are guided at every turn, not just at the closure itself.

Common Mistakes

• Signing the closure but not the full detour route, so drivers are left guessing after the first turn.
• Routing a detour onto streets that cannot handle the traffic or that have their own restrictions.
• Failing to return drivers to the original road at the end of the detour.
• Not coordinating a detour that crosses into another agency's jurisdiction.

What to Check Before Work Begins

• That the detour is signed continuously from the closure back to the original road.
• That the route matches the approved plan and any agency conditions.
• That the streets used can carry the detoured traffic and are not themselves restricted.
• Whether the detour crosses jurisdictions and needs coordination with another agency.