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FHWA Highway Safety Programs


Traffic Sign Principles

While there is much to be said about the design, placement, operation, and maintenance of signs (see, for example, The Traffic Signing Handbook), there are a few key principles that are critical for traffic signs to be effective. As with any traffic control device, a traffic sign should meet five basic requirements stipulated in the MUTCD, namely:

  • Fulfill a need;
  • Command attention;
  • Convey a clear, simple meaning;
  • Command respect from road users, and
  • Give adequate time for proper response.

Even during maintenance operations, it is important for staff to question every sign that they work on to see if it is needed and meets standards applicable to its use. The decision to use a sign at a particular location should be made on the basis of either an engineering study or the application of engineering judgment. Local jurisdictions that do not have engineering staff knowledgeable of the MUTCD should seek assistance from their State transportation agency, another jurisdiction, or traffic engineering consultant. The Local Technical Assistance Program (LTAP) in each State and tribal area can be a valuable resource for this assistance as well.

Traffic Sign Types

The MUTCD specifies three classes of signs defined by their function:

  • Regulatory signs.
  • Warning signs.
  • Guides signs.

Regulatory Signs

The rules of the road—the laws and regulations—are often communicated through regulatory signs. These are important signs to maintain because the absence of, or damage to, a regulatory sign could result in or contribute to a severe crash.

"Regulatory sign: STOP sign""Regulatory sign: YIELD sign"""Regulatory sign: SPEED LIMIT 50 sign

Regulatory signs are usually a combination of black, white and red colors as shown by these examples.

Damaged or missing regulatory signs (especially the STOP, YIELD, ONE WAY, and DO NOT ENTER signs) should be replaced or repaired within hours of the agency having notice of them missing, down, or damaged.

Warning Signs

Warning signs are important because they provide drivers with advance notice of potentially hazardous situations or conditions of the road ahead that may not be apparent. They are particularly helpful to motorists who are unfamiliar with a particular road.

"Warning sign: Turn Ahead sign""Warning sign: Signal Ahead sign""Warning sign: ONE LAND BRIDGE sign"

Warning signs, such as these, have a yellow background.

Damaged or missing warning signs should be repaired or replaced as soon as possible. As a general rule, deficiencies should be corrected within three days of notice.

Guide Signs

Guide signs are used for driver navigation—to help a driver to get to a particular destination. There are a variety of guide signs that display route designations, destinations, directions, distances, services, points of interest, and other geographical, recreational, and cultural information. The absence of these signs could cause motorists to miss their route and destination, resulting in less than efficient navigation. It can also lead to erratic maneuvers, such as slowing or stopping in the roadway and making abrupt turns. For local roads and streets, common guide signs include: street name signs, route signs, and destination and distance signs. General service signs, e.g. the hospital symbol, and general information signs, e.g. the library symbol, are included within the guide sign group.

"Guide sign: Destination sign"

Destination sign

"Guide sign: Street Name sign"

Street name sign

"Guide sign: Hospital sign"

Hospital sign

Guide signs are usually white legend on a green background, but can be other backgrounds, such as brown or blue.

Replacement of damaged or missing guide signs should be done within approximately seven working days from notice, recognizing that timing of the replacement is dependent upon how critical the sign is. For example, a street name sign is essential for emergency responders to find streets and locations on those streets. Also, since many guide signs have to be specially fabricated due to the variation in the sign message, it may take a few days before they can be assembled or purchased.

Signs in Work Zones

Whenever there is construction, utility work, or maintenance being done on the road or roadside, temporary traffic control is necessary, which usually includes temporary warning signs. The warning signs used for this purpose have a black legend and border on orange background. While these are temporary signs, it is important that they be maintained because travel through work zones can be hazardous due to unusual or different conditions that drivers may not expect. These signs should not be allowed to deteriorate much below their original condition. For more information on this topic refer to the MUTCD, Part 6. Appendix C provides three typical traffic control applications from the MUTCD that would likely be used for sign maintenance activities.

"Warning sign: ROAD WORK sign""Warning sign: DETOUR sign"""Warning sign: Flagman Ahead sign

In most cases warning signs such as these have an orange background. (Note: for the signs on left and center, the word AHEAD or the distance [e.g., 500 FT] would fit within the dashed lines.)

The response time frames for correction of missing or damaged signs mentioned above are provided to illustrate relative priority in providing sign maintenance activities. Each agency should adopt a policy that addresses sign repair response procedures and times both for normal work periods as well as after hour needs.