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How a Detour Sign Helps Traffic Flow

November 21, 2018

Smooth traffic flow in a community depends on road access and traffic volume. If a road is closed or blocked ahead without warning it can create slowdowns and confusion. But when drivers are redirected with a detour sign, the city or town can maintain normal traffic flow. Here are situations when such signs are useful.

How Detours Help Drivers

A detour sign may be temporary or long-term. While a temporary sign may reflect regular road work, there may be factors such as mudslides that cause a road to be closed for several months or even years. The damage may be so severe that the local government cannot afford to fix the problem until funding is determined. Until then they make provide a detour that covers just one road or several different roads. Regardless of the reason for the detour, it may not show up on navigation systems, and it may defy require drivers to go outside of their normal patterns. This is why proper signage is so necessary in the case of a detour.

In some cases there may be a need for a series of detour signs, especially if the road is used by hundreds or thousands of drivers or there are multiple turnoffs. Letting drivers know several miles in advance they need to alter their journey is important on freeways or highways. Detours on city streets, however, can be more localized.

Common Reasons for Detour Signs

  • construction work on or near the roadway
  • avoiding a major accident or police scene
  • obstructions or road damage
  • special events
  • strategy to reduce traffic congestion
  • temporary bypass or rerouting

MUTCD Compliance

A detour sign must follow federal standards established by the Manual on Uniform Traffic Control Devices (MUTCD). The detour sign color, for example, must be orange with a black legend, which is also the standard for warning signs in traffic control zones. The bright color and sharp contrast promote visibility and the consistent styling helps drivers notice related signage down the road. Many detour signs have a diamond shape but can also be rectangular. Some signs just say “detour ahead” while others include distance from the intersection, which is usually 500 to 1,000 feet. In the case of construction work, an “end road work” sign should appear 500 feet beyond the work area.

One key regulatory factor is visibility at all times, which means sufficient font size and use of retroreflective coating material. The MUTCD specifies that all signs used at night must be reflective or illuminated to display the same shape and color seen in the daytime. When placed on a highway to redirect drivers to a different highway, the detour sign should also provide the distance.

Dimensions for detour signs may be increased beyond standard values when appropriate, especially for greater visibility. Smaller signs can be used on city streets, if approved by local authorities. Signs can be mounted on posts or portable supports such as barricades for temporary use. They should normally be posted on the right hand side of the road, but in some cases can be posted on both sides of two-way roads. Standard sign height is about seven feet.


Detour signs, like other traffic warning signs, must comply with government regulations at all levels and be easy to read for drivers, even from a distance. Providing adequate warning is an important key to reducing accidents caused by stress, distractions or confusion. To learn more about business and traffic signs, contact Zumar at our Arizona, California, or Washington location.

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