marks), but many roads also operated cars mounted on their own flat cars. Railroads known to have done so include ATSF, CN, CP, CR, CRR, D&RGW, FEC, GN, GTW, KCS, L&N, Monon, MP, N&W, RI, SCL, SLSF, SOO, Southern, SP, SSW, UP, WM, and WP. Transporting new automobiles During the early 1960s, specially built auto carriers rapidly took over rail transportation of newly completed automobiles in North America. They carried more vehicles in the same space and were easier to load and unload than the boxcars formerly used. Ever-larger auto carriers and specialized terminals were developed by Norfolk and Western Railway (N&W) and other carriers. Autoracks were built in three-level configurations carrying automobiles, and with two-levels for vans and light trucks. Autorack and flat car length quickly grew to and then to increase their loading capacity even further. This made them about as long as the average railroad passenger car of the time; if the cars were much longer, they would not be able to operate in interchange service due to clearance on curves. Yet, the railroads could still do better. A major problem left to solve was that the new autorack cars did not provide any protection from theft, vandalism, or severe weather. Individual railroads began installing mesh side screens and solid panels to their racks to protect the vehicles from impact and debris in the late 1960s, and by the early 1970s new racks were being delivered with these side panels. However, thieves and vagrants could still gain access to the automobiles. In 1973 the first fully enclosed racks with continuous side panels, end doors, and roofs were developed to address this problem. Whitehead & Kales, Ford, N&W and DT&I jointly developed a Snap-Pak prototype enclosed tri-level car, NW 400000. The car side was made up of overlapping perforated steel sheets. The ends were protected with two trifold doors, and a corrugated steel roof extended the full length of the car. A competing RailPac prototype was developed by Portec-Paragon, Chrysler, and several railroads. It featured mesh screen side panels, vertically sliding three-piece doors, and a similar roof. The Southern Railway and Greenville Steel Car developed a unique articulated three-unit Autoguard car with single-axle trucks, SOU 599000-599001. The first production fully enclosed racks were delivered in late 1974 and early 1975. The Whitehead & Kales tri-level design, renamed Safe-Pak, was delivered to ATSF, CP, CRR, FEC, NW, SCL, SSW,