Typically, pipelines transport liquid petroleum and some liquefied gases. Since pipelines are usually buried underground, warning signs are used to indicate their presence at frequent intervals along the pipe line route – though not necessarily their exact location, route, depth, or number of pipelines. These signs are located near roadways, railroads, waterways, and along the pipeline’s rights-of-way – as well as where the pipeline intersects a street, highway, or railway.
Often times these signs have a very similar layout in visible yellow, black, and red – though other color combinations are acceptable.