From http://www.railroad.net/forums/viewtopic.php?t=28347 What does this mean? This sounds like how a slug is operated.
That gentleman has some information misconstrued. One of the EL-Cs (former VGN 135) was repainted into N&W... it was undergoing wreck repair at the time of the merger, and was released in the N&W scheme as 235. All twelve EL-cs were sold to New Haven. New Haven converted one of the EL-Cs, N&W 230, nee VGN 130 into a slug.. they called it a diesel hump trailer.
That would explain the confusion I've experienced in the past regarding the number of EL-Cs - it appeared that one vanished sometime before PC. What number did the slug receive? How long did it last?