What type of equipment does not shunt track circuits?

The correct response highlights that all the equipment listed—highway rail vehicles, multiple unit (MU) cars, and track cars—does not shunt track circuits. Shunting refers to the process where a vehicle or object creates a conductive path that completes an electrical circuit, often used for signaling to detect the presence of a train on the track.

Highway rail vehicles, which are designed to operate both on roadways and railways, usually have features that prevent them from shunting track circuits when they are on rail. This characteristic minimizes interference with the signaling systems, ensuring they remain operational and accurate.

Multiple unit (MU) cars, typically used in passenger trains, are equipped to communicate electrically with one another and with the train control systems but are not designed to shunt the track circuits in a way that would lead to misleading signal information.

Track cars, which are maintenance-of-way vehicles, also operate under similar principles. They’re designed for specific tasks related to track maintenance and inspection without impacting the signaling systems that rely on track circuits to function effectively.

By acknowledging that none of these vehicles create a shunt in track circuits, it becomes clear why this answer encompasses all categories: none disturb the balance of electrical signals that track circuits require for safe and efficient