Which item must be included on a pipeline warning sign?

Emergency contact numbers are essential on pipeline warning signs because they provide immediate access to crucial information and assistance in case of an incident, spill, or leak. By having an emergency contact number clearly displayed, individuals can quickly reach the necessary authorities or pipeline operators, enabling a swift response to protect public safety and the environment. This real-time communication can help mitigate risks and coordinate effective emergency response measures.

Including the type of liquid transported, while informative, does not prioritize immediate action in emergencies. Pipeline length and environmental impact statements may also be relevant to understanding the pipeline's purpose and implications, but they do not serve the critical need for rapid communication during urgent situations.