Three types of light rail cars operate on the system, the TW 6000, built from 1974 to 1993, the TW 2000 (the so-called "Silberpfeil"), built from 1997 to 1999, and the TW 3000, which was first introduced into A line service in 2015. The system is extensively used, especially during trade shows on the Hanover fairground like CeBIT or the Hannover Messe. It makes up for more than 60% of the GVH transport association's total traffic, spanning over four cities and two counties. Hanover Stadtbahn is complemented by DB-owned Hanover S-Bahn, a suburban heavy rail network which links the outlying suburbs and towns, as well as Hanover Airport, to the city centre.