This report presents results from the independent evaluation of a field operational test using a fleet of heavy trucks outfitted with a prototype integrated crash warning system. This effort was conducted as part of the U.S. DOT's Integrated Vehicle-Based Safety Systems (IVBSS) program. The system tested included rear-end, lane-change/merge, and lane departure crash warning functions. The goals of the evaluation were to assess safety impact and driver acceptance, and to characterize the prototype system's warning capabilities. Eighteen volunteer drivers from a commercial fleet operated the 10 equipped heavy trucks, accumulating 600,000 miles over a 10-month period. The test period consisted of 2 months of baseline driving, when the system was disabled, and an 8-month treatment period, when the system was enabled and warnings were presented to the drivers. Comparisons were made between baseline driving and the treatment period to determine the effect of system use on driver behavior and performance.