Where are the permissive signals located?

The correct response indicates that permissive signals are found solely in Harrison Yard. Permissive signals are used in rail operations to inform train operators that they can proceed under certain conditions, indicating aspects such as lower-speed movement, which is crucial in yard settings where trains are maneuvered in close quarters and frequent stopping or slowing is necessary.

Harrison Yard, being a crucial location for managing rail traffic, requires these signals to ensure safe movement within the yard environment. They serve as guidance for train crews navigating complex rail infrastructure and operations that might not apply in the same way elsewhere.

In contrast, the other options suggest locations that either do not align with established information regarding the deployment of permissive signals or imply broader areas that typically utilize different types of signals, such as those found along mainline tracks. Mainline tracks generally feature more restrictive signals designed for higher speeds and less frequent stops compared to those used in yard contexts. Thus, focusing specifically on Harrison Yard accurately reflects the specific application and function of permissive signals in that area.