MTA Long Island express train "The Cannonball" Long island Nassau county NY

Express train nicknamed "The Cannonball" on the MTA main line passing thru Nassau county NY on Route 27
This train is a double level train and it runs on weekends from The hamptons Suffolk county NY on the east end of Long island to Penn station in New york city westbound
Its powered by 2 DM30 dual mode diesels
Before going in the tunnels near Penn station the diesel units are then switched to electric mode because it is not permitted to run diesel underground