Early examples of the articulated bus appeared in Europe in the 1920s. In 1938, Twin Coach built an articulated bus for the city of Baltimore; this bus, which had four axles on a long body, was only articulated in the vertical direction to accommodate steep grades. 15 examples of the "Super Twin" were built in 1948, but it was not developed further. According to contemporary coverage, the Super Twin had a capacity of 58 seated and 120 total, with a weight of .