Alternative implementations of a Rear Cross Traffic Alert (RCTA) system intended to actively notify drivers of the presence of rear cross-path traffic when backing were evaluated in naturalistic settings. The feature is one of several emerging technologies designed to assist drivers when backing - in this case, enhancing drivers' awareness of traffic approaching from the rear. The study allowed performance under a range of RCTA system driver interface implementations to be contrasted with conventional and wide Field of View (FOV) Rear Vision systems. Evaluations were conducted using a sample of 70 drivers under naturalistic settings and environments with repeated exposures to backing tasks. The study also made use of a staged conflict situation with a confederate vehicle in order to more precisely quantify driver behavior and system usage across drivers under controlled conflict situations. Contrasts among the experimental configurations allowed for comparisons across the major system design factors, including the use and location of visual warnings, auditory alerts, and Rear Vision system FOV. Results found that use of RCTA systems, which include an audible warning component and Rear Vision screen, reduced backing encroachments into the path of approaching traffic by up to 44%, and enabled drivers to respond faster to the presence of cross traffic as compared to Rear Vision Only systems. Although drivers in this study preferred implementations with a wide camera FOV (180-degree span), related work in this area suggests that preference for camera FOV may be dependent on driver task and functions (e.g., parking, extended backing, trailer hitching, etc).