This paper documents a project to test bus collision avoidance warning systems being performed by Pierce Transit under the auspices of the Washington State Transit Insurance Pool (WSTIP) and the University of Washington under a grant from the Innovations Deserving Exploratory Analysis (IDEA) program of the Transportation Research Board. Commercially available collision avoidance warning systems (CAWS) were modified and adapted by a vendor for use on standard transit buses and installed on 38 buses operating at eight transit agencies, including seven buses at Pierce Transit. Each bus also was equipped with a cellular telematics unit and supplemental cameras with video recording. Buses were operated in normal service for several months, including a three month testing and data collection period. The paper discusses the rationale for the project, technology to be tested, operations and data collection, and some of the early findings from the pilot test.