The use of optimum phase sequences at signalized intersections could save motorists many hours of delay and could result in fewer accidents. However, very little factual information has been availableto guide engineers in choosing between the various signal phasing alternatives. To close that gap, leading and lagging signal sequenceswere evaluated in indiana using a survey of licensed drivers, an examination of traffic conflicts, an analysis of accident records, anda simulation model of traffic flow. The guidelines developed as a result of these activities generally reflect the advantages documented for lagging sequences over leading sequences in a variety of situations. Lagging sequences are recommended for, among other situations, intersections serving heavy pedestrian volumes, diamond interchanges or one-way pairs, and intersections with fixed-time signals. However, when implementing lagging sequences, caution is recommended to prevent situations in which a vehicle could become "trapped" in an intersection as the green phase elapses. This paper appears in transportation research record no. 1324, Communications, traffic signals, and traffic control devices 1991
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