Final answer:
The component that is not present on both cars of a married pair of train cars is typically the operator cab. One car has a full driver's cab while the other has minimal or no control features, with only emergency functionality. This configuration aims to reduce redundancy and costs while ensuring reliable operation as a single unit.
Step-by-step explanation:
The question refers to the different components on a married pair of cars, also known as a coupled set or semi-permanently coupled pair of train cars. The term 'married pair' usually pertains to rail transit vehicles designed to operate with another car. Each car of the pair complements the other by sharing certain systems and features to improve efficiency, safety, interoperability, and maintenance. However, some components are not duplicated because they are intended for the entire unit rather than individual cars.
One component that is not present on both cars of a married pair is the operator cab. Generally, in a married pair, only one car typically has a full driver's cab, while the other might have a rudimentary set of controls or none at all, to be used only in case of emergency or when the cars are being operated independently.
Other systems that tend to be shared and thus not doubled include traction motors, HVAC systems, or electrical systems that are designed to work across the paired unit. The specific arrangements can vary depending on the rail system and the design of the train cars. The rationale behind this configuration is to reduce redundancy, weight, and manufacturing and maintenance costs while ensuring that the pair operates reliably as a single dynamic unit.