Side object detection systems (SODS) are collision warning systems which alert drivers to the presence of traffic alongside their vehicle within defined detection zones. The intent of SODS is to reduce collisions during lane changes and merging maneuvers. This study examined the effect of right SODS on the performance of commercial vehicle drivers as a means of assessing the impact of these systems on safety.In this study, eight professional truck drivers drove a tractor-semitrailer equipped with four different sets of SODS hardware or side view mirror configurations. These subjects had no previous experience with SODS. Subjects were tested with two right SODS (a radar-based system and an ultrasonic-based system), a fender-mounted convex mirror, and, for comparison, standard side view mirrors only. For each case, subjects drove the test vehicle through a set route for one day.The effect of these systems on driver behavior and the extent to which safety may be improved by implementing SODS in combination-unit trucks were assessed based upon the correctness of responses and verbal response times to the question, “Is the right clear?,” which prompted subjects to assess the traffic situation to the right side of the test vehicle. Subject glance behavior during right lane changes and normal driving was also examined. Additionally, a debriefing questionnaire was used to acquire subjects' subjective reactions to these systems.Overall, driver performance with the SODS involved in this study was not significantly improved over that observed with standard side view mirrors. Analysis of the correctness of responses to Right Clear questions showed that subjects' accuracy in assessing the traffic situation along the right side of the vehicle was not improved in the SODS cases, but was improved in the fender-mounted convex mirror case. Verbal response times to Right Clear questions were significantly shorter in the SODS and fender-mounted convex mirror cases than with standard side view mirrors alone. However, this difference may have resulted from a learning effect caused by presenting the standard mirrors first to each subject. Although this data suggests that driver performance was not improved with SODS, it is important to note that no apparent decline in performance was observed either.Subjective responses to debriefing questionnaires indicated that subjects were very positive about the fender-mounted convex mirror. Although subjects reported using the SODS often while driving in the study, glance data showed that subjects only sometimes visually sampled the SODS displays. In general, subjects seemed receptive to the concept of SODS and welcomed any potential improvement to safety.Although it appears that SODS currently have the potential to provide some benefit, overall results of this study suggest that in order for SODS to make significant improvements to safety in the future, more work is needed to improve their performance and design.