The 6 train in the New York City Subway system is primarily a local service that runs along the IRT Lexington Avenue Line in Manhattan and the Pelham Line in the Bronx. It makes every single stop along its route, providing the "granular" service for the East Side of Manhattan. However, there is a nuance: during weekday rush hours in the peak direction (toward Manhattan in the morning and toward the Bronx in the afternoon), a variant called the <6> (Diamond 6) operates as an express service in the Bronx between Parkchester and Third Avenue-138th Street. In Manhattan, the 6 always remains local, while the 4 and 5 trains provide the express service on the same line. In 2026, the 6 train remains one of the busiest routes in the entire world, serving as the "neighborhood train" for the Upper East Side and East Harlem. If you see a circle around the number 6, it's the local; if you see a diamond, it's the peak-hour Bronx express.