That factor, together with creative management controls, has enabled the company to reduce rental rates for the use of its cars by the railroads. TTX Company is one of the largest users of the Transportation Test Center at Pueblo, CO which is operated by the Association of American Railroads. Rather than retire portions of the fleet, TTX cars can often be modified or have new components added to convert or adapt the car to a new type of service. TTX company has over 1,900 employees, with about 300 based in Chicago, IL and the balance at a number of field maintenance centers strategically located around the United States and at four major car repair and maintenance facilities. Since the early 1960's with the introduction of multi-level autorack structures which transport automobiles and other vehicles on flatcars, railroads have gained substantial market share from highway carriers.
Railroads purchase the rack structure which is applied to a flatcar provided to that railroad.
The racks are built to carry either two or three levels of vehicles, depending on rail clearances and the heights of vehicles being transported. Auto sizes and industry requirements have changed over time and rack designs have evolved from simple, open frames to complex, fully-enclosed structures. Standard height flatcars are used primarily for bi-level autoracks. A low level design car was developed to accommodate the taller tri-level autoracks which were introduced in the mid 1960's. When fully enclosed autoracks were introduced in the 1970's a flush deck design car was required.