Shoreliners are used in the non-electrified territory north of Croton-Harmon. Trains often operate to and from Grand Central Terminal and Poughkeepsie and running express south of Croton-Harmon, along with two daily late night shuttle trains running in the non-electrified territory, one in each direction.
Harlem Line
Shoreliners are used in the non-electrified territory north of Southeast. Service between Southeast and Wassaic is mostly operated using two-or-three-car shuttle trains. During rush hour, a few trains run direct to Grand Central Terminal.
Shoreliners operate on the Danbury and Waterbury branches, as well as to provide extra service on the main line during the day. Danbury service includes limited through-service to Grand Central during peak periods, while off-peak Danbury and all Waterbury service operates as shuttles from South Norwalk and Bridgeport.
Before the state of Connecticut acquired used equipment for Shore Line East, several Shoreliner sets would run on SLE service. These have since been transferred to the Metro-North pool.
Models
Shoreliners I and II
The Shoreliners I and II were built in 1983 and 1987, respectively. Based on the New Jersey Transit Comet II and nearly identical, their only difference is the type of lighting used for indicator lights. These cars have doors at each end vestibule, and no center door. The Shoreliner I order includes 39 cars, while the Shoreliner II order includes 36 cars. Cars numbered in the 6200s are owned by Connecticut DOT, while all other cars are owned by the MTA. Four of the Shoreliner I cars were originally equipped with an underfloor head-end power generator, for use behind CDOT's five rebuilt freight locomotives, which lacked HEP generators. The generators were removed when the freight locomotives were replaced by CDOT's rebuilt GP40-2H units. These cars are identified externally by twin square windows at the center of the cars, where the air intake ductwork for the generator was located.
Shoreliner III
Shoreliner IIIs date from 1991; 49 cars were built. This series is based on New Jersey Transit's Comet III. The main differences between this series and previous ones are an added center door and the restroom is located at the center of the cars that are so equipped instead of the end.
Shoreliner IV
The Shoreliner IV is much like the Shoreliner III but the engineers side door has been removed as a safety measure. Based on the NJ Transit Comet IV, they were built in two distinct groups between 1996 and 1998. The first order, from 1996–97, consisted of 50 cars. The second set, built for Connecticut DOT in 1998, consisted of 10 cars. This gives a total count for the order of 60 cars.