Controller of Site Safety (COSS) Practice Exam 2026 - Free COSS Practice Questions and Study Guide

The test here is about who is responsible for establishing and maintaining on-site protection when a stabled train is used to shield workers. The person in charge of safety on the site—the Controller of Site Safety (COSS)—must set up protection before work starts and place the Do Not Move board to warn approaching trains not to move beyond the protected point. This board becomes the visible indication that movement is restricted while the protected area is in place, and the COSS keeps the protection in place until it’s safe to remove it.

The other roles have important duties, but they don’t establish this protection. A signalman controls signals and train movements but doesn’t place the protective marker. The train driver follows the protections shown and does not set them up. The station supervisor handles station operations rather than protection of a specific work site on the line.