Agile Release Trains

The container for the Program Increment Cadence: a long-lived, cross-functional team of teams — roughly 5–12 teams, 50–125 people — organized around one shared value stream, not a single project. Individual initiatives come and go; the train stays:

• Virtual, not org-chart — a train pulls people from wherever they sit functionally; it's a planning and delivery structure layered on top of reporting lines, not a replacement for them. Cisco and John Deere both have public case studies of running multiple ARTs company-wide, each with its own PI cadence running in parallel.
• Long-lived, not project-scoped — the train keeps its own cadence indefinitely; what it's building against changes, but the rhythm and the roster mostly don't. This is the opposite of standing up a project team and disbanding it at launch — stability is the point, so teams get better at the cadence itself over time.

Who actually runs a train day to day is its own topic — see Roles & Responsibilities.