Vehicle collisions have been a significant concern for transit operators. They not only result in property damage, service interruptions and personal injuries, but also affect transit efficiency, revenue and public perception. In addition to collision damage, passenger falls resulting from emergency maneuvers also contribute to an increased potential for passenger injuries and liability. A transit collision ripples through the agency and consumes additional resources to settle claims and results in significant loss of good will. Transit operators and industry stakeholders actively seek solutions to avoid collisions and have recommended that studies be conducted under the US DOT’s Intelligent Vehicle Initiative (IVI) to develop transit collision warning technologies. The primary goal of the Transit IVI program is to develop technical and performance specifications for collision warning systems which can identify hazards that may potentially lead to collisions in complex urban environments and warn drivers accordingly. Based on the recommendations, Federal Transit Administration initiated the Transit IVI Program in 2000. As part of the Transit IVI Program, substantial efforts were carried out to develop frontal and side collision warning systems that can deal with the urban driving environment. Final report.