Sub-problem 2c: Analyzing the Effects of Coordination

One last option we might consider, since most of these runs have assumed a  120-second cycle, is to investigate the possibility of a shorter cycle. However, in order to maintain the ability to coordinate with the other signals along the arterial (which we are assuming to be running the 120-second cycle), we must confine ourselves to a 60-second cycle. This is because the cycle length we use at Museum/Reitz Union must maintain an integer relationship with the 120 second cycle that controls other intersections along Museum Road. As examples, therefore, it could be 30, 40, or 60 seconds in duration. However, we must be cognizant of pedestrian crossing time requirements, and this is likely to eliminate anything less than 60 seconds. Operating the Museum Road/Reitz Union Drive intersection on a 60-second cycle while the remainder of the system operates on a 120-second cycle is commonly referred to as a  double-cycle option; it has the potential to lower delay at our intersection of interest (because of the lower cycle length) while still maintaining the benefits of coordination with upstream signals. The results of this comparison are shown in Exhibit 5-27.

Comparing the results between the 120-second and 60-second cycles illustrates a couple of points. Lower cycle lengths generally result in shorter delays overall, even though capacities go down. Also, the queues are reduced substantially because the red time per phase is less, reducing the time available for queues to lengthen. This is a good strategy where storage lengths are limited, as is the situation in this particular case study. The overall intersection delay was reduced and queues lowered for every movement by between 10% and 50%. Another by-product of this strategy is that the large number of pedestrians will not need to wait as long before receiving a WALK indication.