The California Partners for Advanced Transit and Highway (PATH) Program has been actively involved in the research on controls of heavy vehicles for the Automated Highway Systems (AHS) in the past six years. In this paper, we will present the experimental aspects of the lateral control of a heavy vehicle system in the context of AHS. The experimental heavy vehicle under investigation is a class 8 Freightliner tractor-semitrailer. The hardware instrumentation of the test vehicle is described. Open-loop experiments are conducted to verify the dynamic model of a tractor-semitrailer system. A classical loop-shaping controller and linear robust H∞ controller for the lateral control of the tractor-semitrailer are designed and experimentally verified up to the velocity of 45 mph on a test track with both straight and curved sections (800m in radius).