Pipeline markers and locate colours: what the signs mean

By About Pipelines editors · November 4, 2026

Two kinds of markings tell you something is buried under the ground. Pipeline markers are permanent signs and posts that pipeline companies place along their rights-of-way. Locate marks are temporary paint, flags or stakes left by locators after you make a request through Click Before You Dig. Knowing how to read both, and what they do not tell you, is a basic part of digging safely.

Permanent pipeline markers

Pipeline companies install markers where their lines cross roads, railways and watercourses, along fence lines, and at intervals across open country. They come in several forms: tall posts, flat signs on fences, aerial markers visible from patrol aircraft, and casing vents or test posts near crossings.

A typical marker shows:

• a signal word such as Warning, Caution or Danger
• the product carried, for example natural gas, crude oil or petroleum
• the name of the operator
• a 24-hour emergency telephone number

These elements are standard across North America. In the United States, for example, federal rule 49 CFR 192.707 requires gas pipeline markers to begin with Warning, Caution or Danger, name the gas transported, and give the operator's name and a phone number where it can be reached at all times, in letters at least one inch high. Canadian pipeline companies follow equivalent requirements under CSA Z662 and their regulators' rules.

What a marker does not tell you

Markers are deliberately general. They tell you a pipeline is nearby. They do not tell you:

• The exact location. A pipeline can bend between markers, and a marker may sit on a fence line rather than directly over the pipe.
• The depth. Cover changes with grading, erosion and farming; see how deep gas lines are buried.
• How many pipelines there are. Several lines, owned by different companies, often share one corridor.

Equally, the absence of a marker does not mean there is no pipeline. Distribution gas lines in towns and cities are often unmarked. The original article Pipeline safety: can you spot the right of way? describes other clues that a pipeline is present, such as a cleared strip with no trees or buildings.

Temporary locate marks and the colour code

When you request a locate, each utility with lines in the area marks them with paint, flags or stakes in a standard colour. Canada's one-call centres and the Canadian Common Ground Alliance use the same uniform colour code as the United States, based on the American Public Works Association (APWA) system:

Marks may also include letters identifying the utility, arrows showing direction, the width of the facility, or a note that a line is "offset" from the mark. Your locate sheet explains the symbols used.

Working with locate marks

• Check that every utility has responded before you start. A missing colour may mean a utility has not yet visited, not that nothing is there.
• Respect the tolerance zone. The mark shows the approximate centre of the line. Utilities define a zone on either side within which you must expose the line by hand or hydrovac before using machinery.
• Protect the marks. Rain, mowing and traffic wear them away. If marks disappear before the work is done, request a new locate.
• Watch the expiry date. Locates are valid only for a set period, which varies by province and utility.
• Near transmission pipelines, the Canada Energy Regulator's rules also require the pipeline company's written consent for ground disturbance within 30 metres of the line. See the CER's damage prevention page.

Using a marker in an emergency

The emergency number on a pipeline marker is there for anyone who sees signs of a leak or damage. If you notice a hissing sound, a petroleum or rotten-egg smell, dead vegetation, bubbling water or a vapour cloud near a right-of-way, move away and upwind, call 911, and then call the number on the nearest marker. The original page What should I do if I see a pipeline leak? sets out the steps, and our guide to what natural gas smells like explains the warning signs.

Sources

• U.S. Code of Federal Regulations, 49 CFR 192.707, Line markers for mains and transmission lines
• Canada Energy Regulator, Damage prevention
• Common Ground Alliance, Best Practices, Appendix B: Uniform Color Code and Marking Guidelines
• Gopher State One Call, What do the marks mean? (APWA colour code)