The Comet railcar is a class of locomotive-hauled railcars that was first designed in the late 1960s by Pullman-Standard as a modern commuter car for North American rail lines. Later, the Comet moniker was adopted by NJ Transit for all of its non-powered single level commuter coaches. Additional series of cars bearing the Comet name, based on the original design, have since been built by Bombardier Transportation and Alstom. The successful design was adopted by numerous commuter agencies. History Comet I These cars were the first of the Comet series, built by Pullman Standard in 1970–73 for the New Jersey Department of Transportation and used the Erie-Lackawanna Railroad's diesel-hauled commuter services. These railcars were named after the Jersey Central train Blue Comet. These were considered state of the art at the time, due to their all-aluminum body shell construction as well as their use of head-end power (HEP). Their automated entrance doors, designed for use with low platforms only, earned them the nickname "Sliders". 155 cars were built, with 35 cab cars, 110 trailer coaches and 10 bar cars. In 1987, the fleet was rebuilt by Bombardier at Barre, Vermont, with all 35 cab cars and a number of trailer cars receiving high doors, for ADA access and future compatibility with high platforms. They were given NJ Transit logos adjacent to the entrance doors at this time, as NJ Transit had taken over EL commuter service. The bar cars were converted to standard coaches. The low door cars were retired from service in 2005. 25 of the cars were sold to Utah Transit Authority (UTA) for the FrontRunner service, and 20 were leased to Metrolink in 2008 to help with an acute car shortage there. In March 2011, Metrolink returned the cars to FrontRunner upon the expiration of the lease. Metrolink also leased 15 cars directly from New Jersey Transit in 2009. These cars have not been used since 2011. The Comet I cars have become popular with western commuter lines as the low door setup is compatible with the low-platform stations in use. Eight Comet Is were sold to SEPTA, but are now out of service and put into storage. Some of these have recently been used in work service. NJ Transit retired the last of its Comet Is in March 2009. The Comets that were not sold to SEPTA, Metrolink, UTA or to private railroads and museum fleets