Clocker trains were started by the Pennsylvania Railroad between Philadelphia and New York; until the 1950s weekday trains departed New York and Philadelphia on the hour through the day, giving rise to the Clocker name.
After the Amtrak takeover of the Northeast Corridor the no-longer-hourly "Clocker" service was targeted at commuters making local stops bypassed by the high speed Metroliner and individually named trains.
During the 1990s NJ Transit contracted with Amtrak to accept monthly NJ Transit passholders on the Clocker trains.
Soon the Clockers were primarily used by NJ Transit commuters with only a handful of riders taking the trains to or from Philadelphia; the Clockers were much faster (and more comfortable) than a typical NJ Transit train, but slower and more crowded than a typical Amtrak train causing the former's riders to prefer the trains and the latter's riders to avoid them.

With most Clocker riders using NJ Transit tickets, NJ Transit supplied new ALP-46 locomotives to haul the trains' Amfleet coaches; Amtrak soon discontinued the Clocker service altogether and sold the capacity slots to NJ Transit for new Trenton express trains.
The Clocker last ran on October 28, 2005, and thereafter NJ Transit began several extra Trenton-New York express trips.
Clocker trains were started by the Pennsylvania Railroad between Philadelphia and New York; until the 1950s weekday trains departed New York and Philadelphia on the hour through the day, giving rise to the Clocker name. After the Amtrak takeover of the Northeast Corridor the no-longer-hourly "Clocker" service was targeted at commuters making local stops bypassed by the high speed Metroliner and individually named trains. During the 1990s NJ Transit contracted with Amtrak to accept monthly NJ Transit passholders on the Clocker trains. Soon the Clockers were primarily used by NJ Transit commuters with only a handful of riders taking the trains to or from Philadelphia; the Clockers were much faster (and more comfortable) than a typical NJ Transit train, but slower and more crowded than a typical Amtrak train causing the former's riders to prefer the trains and the latter's riders to avoid them.
With most Clocker riders using NJ Transit tickets, NJ Transit supplied new ALP-46 locomotives to haul the trains' Amfleet coaches; Amtrak soon discontinued the Clocker service altogether and sold the capacity slots to NJ Transit for new Trenton express trains. The Clocker last ran on October 28, 2005, and thereafter NJ Transit began several extra Trenton-New York express trips.
Northeast Corridor Line