Open autorack (bi/tri-level)

The open autorack emerged as a direct response to the explosive growth of the American automobile industry in the postwar era. Prior to their development, new vehicles were shipped in conventional boxcars, a method that was increasingly inadequate as annual automobile production climbed into the millions. Early experiments in the 1920s and 1930s with double-deck flatcar arrangements pointed toward a solution, but it was not until the late 1950s that a practical open rack design gained widespread acceptance. The Saint Louis-San Francisco Railway, known as the Frisco, played a pivotal role in establishing the modern autorack concept when it fielded a prototype tri-level rack on an 83-foot flatcar in January 1960, capable of carrying twelve automobiles. That same year, the Atchison, Topeka and Santa Fe Railway and the Southern Pacific were conducting their own trials with tri-level racks supplied by manufacturers including Whitehead and Kales and Dana-Spicer, mounted on General American-built flatcars. Within months of these early successes, numerous other railroads placed orders with a growing list of suppliers that included American Car and Foundry, Thrall Car Manufacturing, Evans Products, and Paragon Bridge and Steel. Through the early and middle 1960s, the open autorack rapidly displaced the boxcar and highway trailer-on-flatcar method as the dominant means of transporting new automobiles by rail. Car lengths grew quickly from the original 83-foot designs to 87 feet and ultimately to 89 feet, the practical maximum for interchange service given clearance restrictions on curves. Bi-level configurations were developed alongside tri-level designs to accommodate taller vehicles such as vans and light trucks, which could not fit within the reduced vertical clearances of a three-deck arrangement. Specialized automotive distribution terminals were constructed by railroads including the Norfolk and Western to handle the large volumes of vehicles moving through the network. Most autoracks during this period were mounted on flatcars leased from companies such as Trailer Train, North American Car Corporation, and Merchants Despatch, though a number of railroads including the Santa Fe, Southern Pacific, Union Pacific, and Southern Railway operated cars on their own flatcar fleets. The principal limitation of the open autorack design was its vulnerability to theft, vandalism, and weather damage. Because the early racks had no side enclosures beyond light mesh screens added in the late 1960s, vehicles were exposed to debris, brake sparks from other trains, and opportunistic theft during transit. These problems prompted the railroad and automotive industries to develop fully enclosed autorack designs beginning in the early 1970s. Whitehead and Kales, working in conjunction with Ford Motor Company, the Norfolk and Western, and the Detroit, Toledo and Ironton, produced the first enclosed Snap-Pak prototype around 1973, leading to the gradual transition away from purely open designs toward the enclosed and screened autoracks that became standard in subsequent decades. Nevertheless, the open and semi-open autorack established the fundamental operational template that the enclosed designs would follow, and cars built to the basic 89-foot bi-level and tri-level configurations continued to operate in modified form for many years.

Open autoracks of the type designated VO by the Association of American Railroads were typically built to a nominal length of 89 feet and rated at approximately 70 tons capacity. The rack structure itself was a separate superstructure bolted or welded onto a standard heavy-duty flatcar, a design approach that allowed the rack to be removed and replaced independently of the underframe. Tri-level cars in this category could accommodate as many as fifteen compact automobiles or twelve full-size vehicles depending on the era of construction, while bi-level variants were configured for taller light trucks and vans, generally carrying eight to ten of those vehicles. The decking on each level was typically constructed of wood planking set into steel framing, providing grip for vehicle tires during loading and transit. End ramps, either hinged from the car ends or supplied as separate portable sections, allowed vehicles to be driven up to each deck level during loading at terminal facilities. The flatcars underlying the rack structures were generally 89-foot units riding on two four-wheel trucks, built by manufacturers including General American Transportation, Thrall, and Pullman-Standard. Because autorack cars presented an unusually tall and broad profile to the wind, they required careful attention to truck and suspension design to maintain acceptable ride quality and stability at road speeds. The height of a loaded tri-level car pushed the overall clearance envelope to its practical limits on many routes, necessitating clearance surveys before autoracks could be operated on a given line. Side screens of expanded metal mesh were commonly added to open racks during the late 1960s to provide some protection against debris and reduce wind-induced vehicle damage, representing an intermediate step between the original fully open configuration and the later fully enclosed designs.

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