What is an AC MOTOR STOP sign?

• A. A sign placed in the Catenary to indicate the end of contact wire. Electric engines and MU equipment must not pass this sign with their Pantograph(s) up.
• B. A sign indicating the start of a maintenance zone.
• C. A sign indicating a reduced speed zone ahead.
• D. A sign indicating the next station stop.

Answer: (A)

An AC MOTOR STOP sign marks the end of the overhead contact wire in the catenary system. It tells electric engines and MU equipment not to pass this sign with their pantographs up, because beyond that point there’s no live contact wire to draw power from and continuing with the pantographs raised can cause damage or create unsafe conditions. The pantograph is the apparatus that collects electrical power from the wires, so keeping it up past the end of the contact line would be inappropriate and risky. Other signs refer to different situations—maintenance zones, speed restrictions, or station stops—and don’t pertain to the end of the live catenary or the need to lower pantographs.