were abandoned. On 16 October 1925, the Wiener Stadtbahn, which had been taken over by the municipality of Vienna, was absorbed into the tramway network's tariff system. In 1929, the peak tram fleet was achieved, and in 1930 the network reached its maximum length, . In the interwar period, Vienna had more people than today. In 1910, the city reached 2.1 million; after First World I began, the population decreased significantly, reaching its lowest level at the time of the 1991 census, at about half a million. Between the wars, the tramway was virtually unrivalled as a city transport in Vienna. After the Anschluss with Germany's Third Reich, the tramway network was changed on 19 September 1938 from left hand traffic to right hand traffic. During World War II, tram operations continued, for as long as Vienna remained spared from fighting. Its peak haulage, on the then still extensive route network, was almost 732 million passengers, in 1943. That year, 18,000 people found work on Vienna's tramways. In 1944–1945, however, when Vienna was bombed extensively, operations had to be gradually closed down, until the last line, the O-Line, was closed on 7 April 1945. After World War II Following the Battle of Vienna in early April 1945, the first five lines were able to be returned to service on 28 April. Most of the city's fleet of 4000 trams were badly damaged, 400 of them beyond repair. The task of restoring the network would not be completed until 1950; some short sections of track were never put back into operation. In 1948, Vienna acquired second hand trams of Type Z (road numbers 4201-4242) under the Marshall Plan from New York. These trams, which became known as Amerikaner (Americans), were a little wider than other trams used in Vienna. They could only be put into operation on tracks that had a wider track spacing, left over from the steam tramways. An example of these more widely spaced tracks was Line 331 to Stammersdorf. The Amerikaner were comparatively modern, because they were equipped with air-operated doors and automatic retractable ramps. Additionally, the seat backs could be adjusted, so that all seated passengers could always face towards the direction of travel. Some of the major modifications required for the Amerikaner to be able to run in Vienna were carried out by Gräf & Stift in Wien-Liesing. Until the 1950s, the network was still