Following the first decade of the 20th century, several developments would affect the design of the school bus and student transport. As vehicles evolved from horse-drawn to "horseless" propulsion on a wider basis, the wagon bodies of kid hacks and school cars were adapted to truck frames. While transitioning into purpose-built designs, a number of features from wagons were retained, including wood construction, perimeter bench seating, and rear entry doors. Weather protection remained minimal; some designs adopted a tarpaulin stretched above the passenger seating.