Until the passage of the Surface Transportation Assistance Act of 1982 (STAA), many eastern states did not allow the use of twin trailers, 48-foot trailers, or 102-inch wide trailers as a matter of routine practice. Currently all of these configurations must be allowed on the interstate system and certain designated routes. Because there remain many unanswered questions concerning the safety of these larger configurations, this study was undertaken to examine potential problems that may arise in their use and how such problems may be minimized or avoided altogether.