What is the term for specialized equipment operated on track for inspection or maintenance purposes?

The term for specialized equipment operated on track for inspection or maintenance purposes is "Track Car." Track cars are vehicles designed specifically for maintenance tasks, such as inspecting the condition of the rails and other infrastructure components. They may be equipped with tools and instruments necessary for maintenance crews to perform their work effectively.

The other options refer to different concepts not specifically related to inspection or maintenance equipment. Control Block pertains to more general operations related to signaling and communication, M-Series Equipment typically involves a classification of certain types of railway vehicles or systems, and Equipment is too broad a term without any specific connection to the function described in the question. Therefore, "Track Car" is the correct choice, reflecting the precise terminology used in the railway industry for vehicles dedicated to maintenance and inspection activities.