Presignals: Current Applications and Issues

Applications and technical issues related to using presignals to improve the safety of at-grade light rail transit crossings are discussed. A presignal installation has roadway traffic signal heads placed ahead of a downstream, signalized frontage roadway intersection and the stop bar displaced in advance of the grade crossing. This signal ensures that a vehicle stops at a red traffic light before the grade crossing area and the clear-storage zone between the grade crossing and downstream intersection. Presignals have been used for many years and are a state standard in Michigan and South Carolina. However, a tragic accident in which a school bus was hit by a METRA commuter train in Fox River Grove, Illinois, brought renewed attention to this treatment. The state of Illinois installed a presignal at the Fox River Grove grade crossing and has developed a statewide policy for the use of presignals elsewhere. Background is provided on presignals, including alternative types of queue control using traffic signals. The key design features of a presignal installation are highlighted. Outstanding technical issues are identified, including future research to refine policies or warrants for presignals and applicable design standards.