Nearly 46% of bus accidents across the United States each year occur on the left or right side of the bus. These collisions result in property damage, and they can negatively impact on revenue operations and public perception. The first commercially available side collision warning system for transit buses entered the market in 2004. The system is designed to help bus operators navigate tight maneuvers at speeds below 15 mph and with lane changes at speeds greater than 15 mph. This report presents the findings of a federally sponsored, independent evaluation of the system. The evaluation aimed to address three key goals: (1) to assess operator usability and acceptance of the technology; (2) to assess the return on investment of the technology; and (3) to identify lessons learned and other information that would be useful to agencies considering deployment of this technology or similar technologies. The evaluation team worked with three participating agencies to gather a wide range of data through interviews, surveys, focus groups, interviews, site visits and observations, collision records, and cost data. The findings indicated that operators were optimistic about the potential of a side-impact collision warning device and that the side object detection system (SODS) was useful in certain situations and that it had in fact prevented collisions, in particular those that involved detecting an object in the operator’s blind spot. However, operators did not find the system usable in its current design, particularly with regard to the quality and frequency of visual and audible alerts. Additionally, the return on investment analysis indicated that the early-adopters of this technology are not likely to experience a return on investment within 12 years, the typical life of a bus. However, agencies investing in this type of technology in the future may not face the same institutional challenges as the early-adopters or may have different collision characteristics, and thus may see a sooner return on their investment. These institutional issues can be significant if not properly accounted for prior to system deployment. All transit agency stakeholders—operations, maintenance, training, safety, and claims—must have a clear understanding of the technology capabilities and its limitations. Inconsistency in system installation resulted in varying operational characteristics among the different bus models and influenced operators’ perceptions of system reliability. Additionally incomplete training and system activation prior to all affected operators being trained led many operators to incorrectly understand the technology, system operation, and system limitations. Similarly, incomplete maintenance staff training led to improper troubleshooting and testing of the technology. Agencies considering SODS or similar safety devices for their transit fleet should first consider the lessons learned experienced by these agencies.