On-board Camera/Video Imaging Systems (C/VISs) for heavy vehicles display live images to the driver of selected areas to the sides, and in back of the truck's exterior using displays inside the truck cabin. They provide a countermeasure to blind-spot related crashes by allowing drivers to see objects not ordinarily visible by a typical mirror configuration, and to better judge the clearance between the trailer and an adjacent vehicle when changing lanes. The Virginia Tech Transportation Institute is currently investigating commercial motor vehicle (CMV) driver performance with C/VISs through a technology field demonstration sponsored by the National Highway Traffic Safety Administration (NHTSA) and the Federal Motor Carrier Safety Administration (FMCSA). Data collection, which consists of recording twelve CMV drivers performing their daily employment duties with and without a C/VIS for four months, is currently underway. This paper presents preliminary results of CMV driver lane change performance with and without a C/VIS. The results are based on currently-available data collected from five CMV drivers over a one-month baseline period and one month of driving with the C/VIS enabled. A total of 440 randomly-sampled lane changes were analyzed. Drivers' mean distance to an adjacent vehicle at the time of the lane change, their visual sampling behavior prior to the lane change, and their execution of the lane change are considered in this paper. Because data collection is still underway, these results should be considered as preliminary and may change once the entire dataset is analyzed. This paper does, however, inform researchers about the progress of this technology field demonstration and the planned analyses.