Investigation of the Effectiveness of Boulevard Roadways

The state of Michigan has been constructing directional crossovers in the medians of boulevard roadways since the 1960s to alleviate the congestion and interlocking that were occurring at bidirectional crossover locations. The objective of this research is to investigate the safety benefits of divided roadway and directional crossover median designs. An investigation of the mean accident rates of roadways with boulevards compared to the mean accident rates of roadways with continuous center left-turn lanes revealed that there is a significant difference, with boulevard roadways having a lower mean accident rate for those Michigan roadways investigated. Investigation into the difference of the mean accident rates for boulevard roadways with medians of different widths indicated that roadways with medians greater than 9.15 m (30 ft) but less than 18.30 m (60 ft) had the lowest mean accident rate of the three median categories investigated. The difference was significant for most accident types when compared to roadways with medians less than or equal to 9.15 m (30 ft) and greater or equal to 18.30 m (60 ft). The investigation of the accident rates for boulevard roadways with directional and bidirectional signalized crossovers, while not conclusive, indicated that boulevard roadways with direction crossovers had a lower mean accident rate than boulevard roadways with bidirectional crossovers for signalized roadways.