Two B1-class trams were built as part of the order for 28 A1-class trams in 1984 and 1985. The B-class trams used the same traction equipment as the Z3 and A-class trams, and were designed for operating on the light rail lines. They were originally built with both trolley poles and pantographs, as well as movable steps to allow railway platform and street level boarding, however this concept was later abandoned when low-floor platforms replaced railway-height ones at the converted light rail stations. Both B1-class trams had been withdrawn by 17 December 1985.