Traffic Flow Study for Downtown Keene (current configurations)
The following study was performed to analyze the dynamics of the traffic around Central Square. The study targeted the efficiency of the traffic flow from the tributary feeders for the current road configuration. The method used, analyzed the actual flow primarily focused on the number of waiting vehicles that could be serviced by one light cycle. The number of vehicles that were stopped/waiting for the light cycle is not relevant regarding the service provided as they were all serviced, and therefore no percentage of vehicles serviced would be applicable.
The waiting queues documented in the Stantec study and are not a measure of the efficiency of the current configuration. They do not reflect the throughput of the current road system. The modeling method and assumptions were not disclosed putting in question the results published, relating to queued traffic. However, the queuing measurements shown in this study of the existing configuration, do reflect closely the current traffic queues observed in the Stantec study.
The Stantec model has several points of failure, (flow interruptions not addressed), based on the single lane configurations. The current system does not have these problems. There was no assessment of traffic flow variations based on the single lane restrictions. They will be addressed specifically in another section based on design analysis.
There are several changes that could be made with a more intelligent signaling system to gain efficiencies over the current configuration. It should also be noted unlike the Stantec proposed configuration there are no single points of failure that would cause backups affecting the traffic flows in this proposal!
Study Discussion
There were six studies performed. The measurements were performed based on the busiest time of day as identified in the Stantec study.
Propositions
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The time of day was from 5PM to 6PM. (overlapped both times).
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They were performed on Monday, Wednesday, Thursday, and Friday.
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The primary evaluation was based on the number of vehicles that did not clear the light cycle.
( not on the number of vehicles queued by the red-light cycle).
Measurements Assessment
Normally a matrix for each flow would be provided showing the percentage of vehicles that were not serviced by one light cycle. However, the study measurements showed the all traffic queued was serviced in one light cycle. It was also observed that there were numerous vehicles that made the light cycle that were not in the waiting queue, in most cases, in similar numbers to the queued traffic, indicating double the queued traffic with the current signal timer settings.
Exception: There is minor exception, traffic entering from Roxbury did not completely make a single light cycle. This was observed on less them 1 out of 8 or more cycles. There are options, (right turn signal intervals), that can address this problem.
Resulting Conclusions
Normally a matrix for each flow would be provided showing the percentage of vehicles that were not serviced by one light cycle. However, the study measurements showed the traffic queued was serviced in one light cycle. It was also observed that there were numerous vehicles that made the light cycle that were not in the waiting queue. This implies
adequate capacity for existing and future traffic and the potential to shorten or manage cycles more efficiently in the future. Dynamic signal using new equipment configurations could adjust to traffic, providing even greater efficiencies.