Valmet Nr I

Nr I is a class of articulated six-axle (B′2′B′ wheel arrangement), chopper-driven tram operated by Helsinki City Transport on the Helsinki tram network. All trams of this type were built by the Finnish metal industry corporation Valmet between the years 1973 and 1975.

Between 1993 and 2004 all trams in the class were modernised by HKL and redesignated as Nr I+ class. Currently HKL classifies them as NRV I.

Overview

Nr I were the first type of articulated tram operated by the HKL. The design of the Nr I type trams was based on the GT6 type trams built by Düwag for various cities in western Europe since 1956, but the Nr I incorporated several technological innovations that had not been available when the GT6 was designed. The Nr I trams were delivered by Valmet between 1973 and 1975, with the first seven trams delivered in 1973, further 18 delivered in 1974 and the final 15 in 1975. As the first mass-produced tram type in the world, the Nr I featured thyristor chopper control. The first tram of this class entered revenue-earning service on 16 December 1973 on line 10. Although the trams of this type are numbered 31 to 70, the first unit was not the 31st tram to be used by the HKL. The HKL tram numbering system had been reset in 1959, with the numbering of new trams delivered that year beginning from 1.