Contact!: In Terms of Operational Stability and Safety, Everything Rides on the Sensitive, Coin-Sized Area Where Wheel and Rail Make Contact

The wheel/rail interface and the design and management of the components that affect it is potentially one of the most costly elements in railroading. When well-handled, it can improve vehicle and track forces, creating opportunities for increased speeds and improved capacity, as well as improvements in fuel economy, safety, and reduced environmental impacts from noise. Those are the findings of a report published by the Association of American Railroads' Transportation Technology Center, Inc. and Railinc. The management of the interface remains a developing technology, the report notes, with the long-term effects of wheel and rail profile design not fully understood. Additionally, advantages from improving profiles, wheel and rail materials, and lubricants have not been realized, and methods for monitoring conditions at the wheel/rail interface need additional refinement. An annual research review in March 2009 examined improved vehicle and track performance, increasing wheel and rail component life through improved wheel/rail interface management and design, and top-of-rail friction control. A number of developments are described. One major development is the deployment of the long-travel constant-contact side bearing (CCSB), created to improve performance of 125-ton double-stack articulated cars, introduced in the late 1980s. Today, CCSBs are required on all new cars and all of the various car modifications covered by AAR Rule 88 to control a phenomenon known as truck hunting and create better wheel load equalization.