Shared Services comprises of the specialty roles, people, and services that are compulsory for the accomplishment of an Agile Release TRAIN (ART) or Solution Train but these shared services cannot be dedicated full-time. The need of Shared Services arise when there may be a lack of a specific EXPERTISE available. Also, the requirements of the ART may change, making full-time availability UNREALISTIC. To cater this scenario, Shared Services supports development by quickly focusing specialty expertise on the areas of the system or Solution that require unique knowledge and skills. They participate in Program Increment (PI) planning along with Pre- and Post-PI Planning.

The benefits of utilizing the Shared Services in Scaled Agile framework is immense, to mention a few, it can save time IMPROVES productivity by eliminating the need for individual development team, drives efficiency throughout the organization, ACCELERATES speed to market of quality software products. One of the biggest benefits include, working together with agile teams to fulfill the dependencies that happen/are encountered during PI execution.

While not dedicated to the train, Shared Services must travel with it, as the train has to carry some of their cargo, too. 

People who can participate as a likely Shared services normally have the following specialized skill - Agile and Software/Systems Engineering Coaches, Information architecture, IT Service Management and deployment operations, Internationalization and localization support, etc.(to mention a few)