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Details on Detour Signs

February 17, 2020

A detour sign can pop up at any time on a familiar road or highway. Many times these signs are just temporary until road work is completed, while other times it can be a long-term scenario. It’s becoming more common for local traffic control officials to use portable electronic signs, since they can be used for a wide number of reasons beyond detours. Here are important points to know about using signs on streets to redirect traffic for alternate routes.

Regulations for Traditional Detour Signs

Most detour signs are diamond-shaped with orange or yellow backgrounds, but they can also take other forms. One way arrow signs that say “detour” are common as well in certain situations. Some detour signs give a distance, such as “500 ft,” to warn drivers when to expect an upcoming routing change. Those situations may include a speed limit sign within close proximity. Regulations regarding all road signs in the United States originate from the Federal Highway Administration, which regularly updates its Manual on Uniform Traffic Control Devices (MUTCD).

Alternative routes are planned by local officials who work with construction crews to create temporary traffic control (TTC) zones. These zones often require posting warning signs near intersections where routing changes occur. A detour sign may be installed for both motorists and pedestrian/bicycles.

All of these signs must meet MUTCD requirements, which mandate that detours be adequately marked. Since not all detour signs are interchangeable, it’s best to review the manual to meet compliance for specific situations. Warning signs for road work, for example, must be orange, which drivers recognize from a distance as a message to proceed with caution. The MUTCD further mandates specifications for height and reflectivity, in addition to design features and placement in relation to the road or work site.

The detour sign must be placed ahead of the route change to warn drivers. In some situations it’s necessary to place an “end detour” sign where the original route is reestablished.

Portable Detour Signs

There are a variety of sign types that can be used, from aluminum to roll-up versions, but it’s still important to check the manual to ensure compliance. A portable changeable message sign (PCMS) is an electronic machine, often on a trailer, that allows for flexible electronic messages. These traffic control devices, usually powered by battery or solar energy, may communicate multiple messages to drivers to inform them about specific local road changes and conditions. Backgrounds are black while the LED display needs to be yellow or orange.

PCMS devices are more likely to appear on city freeways, but can also be placed on various types of roads. They are useful to alert drivers on work zones and special events.

Long Detours

Detours within a city tend to be short, while the longer distances are typically between cities on highways or freeways. Sometimes extended detours can affect travel through different states, like the bridge work done on I-15 in Arizona in May 2019, which affected traffic from both Nevada and Utah. That particular detour extended for 220 miles in the Northwest corner of Arizona and was overseen by the Arizona Department of Transportation (ADOT). In that scenario, ADOT restricted traffic to one side of the freeway with one travel lane in each direction. It required loads wider than 10 feet to take a detour.


Temporary alternate routes are common for local and state jurisdictions, as flexibility allows for various types of signage to convey the message to drivers. Contact Zumar at our Arizona, California or Washington location for more information on detour signs or any other type of signage.

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