SBB Lightweight Steel Passenger Cars - Comfortable and Successful - The use of the first lightweight steel coaches on the route Zürich-Geneva starting in 1937 began the "New Era" on the SBB in passenger service between cities. Due to the growing competition in the Thirties from automobiles at that time, very modern passenger cars were developed in cooperation between the SBB and SWS (Schlieren). The lightweight concept of these two organizations with a reduction in the weight of the cars unloaded from between 36 and 39 metric tons to between 25 and 27 metric tons enabled faster speeds on curves and a definite increase in train speeds. The doors on the sides of the cars were moved from the ends of the cars to the area between the trucks because of the requirement for easier boarding of the cars and for as low a center of gravity in the cars as possible. This innovation as well as the double doors originally designed for regional passenger trains enabled shorter stops in stations. As a result cars with simple entry doors followed later. These cars were built up to the end of the Sixties, and during this time different designs and arrangements of doors as well as different window arrangements and other modifications resulted in a great number of variations in lightweight steel cars, including cars with center entry doors and later even with entry doors on the ends. The initial arrangement of the doors towards the cars" center had become necessary in order to improve the running characteristics and gain space for the trucks, which were set wide apart from each other. The costs of this design paid off, and the SBB used its comfortable, lightweight cars exclusively in city-to-city long distance service for almost 3 decades in the lightweight express trains created at that time. It was the middle of the Fifties before the SBB's financial situation allowed it to purchase lightweight steel coaches in large numbers and subsequently use these cars in regional passenger service. During this phase these cars were also equipped with control lines for push/pull service. A total of about 2,400 units were built and they formed the backbone of the SBB's passenger car roster. The lightweight steel coaches made up a harmonious whole with the class Re 4/4 I electric locomotives (with two trucks), which were perfect in terms of technology and appearance. From 1947 on these cars and locomotives in particular consistently defined the look of Swiss train consists.