A detour sign tells drivers a stretch of road ahead is closed and points them toward an alternate route back to their original path. They show up in short-term situations and in detours that last for months, so it helps to know what the signs mean and who’s responsible for putting them there.
State and local departments of transportation place most detour signs, but they’re not the only ones. Cities, school zones, construction crews, and police departments can all post detour signs when they need to redirect traffic, whether that’s for road work, a school event, or an active accident scene.
Detour routing also uses color to communicate direction at a glance. Some agencies mark one color for a route headed north and a different color for a route headed south, so drivers merging from side streets can follow the correct color back onto the detour without re-reading every sign.
Common reasons you’ll see a detour sign include:
Traditional detour signs are diamond-shaped with an orange or yellow background and black lettering, in line with MUTCD standards for signs warning of a temporary change to normal traffic patterns. Along the detour route, additional signs mark the distance to the point where traffic rejoins the original road, often in increments like “500 FT,” and a final sign marks the end of the detour where drivers merge back.
The MUTCD also sets standards for reflectivity and mounting height, so a detour sign is visible to drivers at night and from a safe following distance in daylight.
Not every detour is fixed in place with a permanent sign. For temporary or fast-moving situations, crews often use portable changeable message signs (PCMS), electronic trailer-mounted signs that run on battery or solar power. These can be rolled into place quickly, programmed with specific detour instructions, and moved again once the detour ends, which makes them useful for short-duration work zones and emergency reroutes.
Most detours reroute traffic for a few blocks or a few miles, but some run much longer. In May 2019, the Arizona Department of Transportation managed a 220-mile detour on I-15 after a rockslide closed the highway in the Virgin River Gorge, rerouting traffic that normally passed between Nevada and Utah. The detour restricted loads wider than 10 feet, since the alternate route couldn’t safely accommodate them, and stayed in place for months while crews cleared and stabilized the roadway.
A detour sign means the road ahead is closed and marks the way back to it, whether that’s a construction crew rerouting a block for an afternoon or a state DOT managing a detour that spans hundreds of miles. Contact Zumar at our Arizona, California, or Washington location for detour signage, portable message signs, or help planning signage for a long-term reroute.