Additional expressways serve as bypasses and local routes, especially around Dortmund and Bochum. Due to the density of the autobahns and expressways, Bundesstraßen are less important for intercity traffic. The first Autobahns in the Ruhr opened during the mid-1930s. Due to the density of the network, and the number of alternative routes, traffic volumes are generally lower than other major metropolitan areas in Europe. Traffic congestion is an everyday occurrence, but far less so than in the Randstad in the Netherlands, another polycentric urban area. Most important Autobahns have six lanes, but there are no eight-lane Autobahns in the Ruhr.