About the research
Maintaining arterial corridors with a high volume of traffic and high density of intersections is a matter of primary importance to the traffic division of any city. Traditionally, the traffic division maintains these traffic signals in three ways: entirely pre-programmed (pre-timed signals), partially based on actuations (partially actuated), or entirely based upon sensor actuations (fully actuated). However, all these type of signals need some retiming every three to five years, which involves a lot of human effort in solving complicated optimization problems. In order to circumvent the effort of retiming, adaptive control signal technology (ASCT) was developed. ASCT tends to maximize the capacity of the existing system, which reduces the cost to both the users and the system operating agencies. However, the initial set-up has been found to be labor intensive.
The City of Omaha has planned to set up ASCT on the Dodge Street corridor. This will involve setting up adaptive signals along nine intersections of the corridor and six along other major roads along the corridor. A detailed evaluation of the performance of the ASCT is to be studied in this project to determine its benefits to the City of Omaha.
The objectives of this study is to determine the efficiency of the ASCT on Dodge Street. The following benefits of the Dodge Street are to be studied in detail:
- Operational Efficiencies during Normal Conditions – The ASCT is expected to improve the operation of a corridor under normal condition. The before/after study will involve dealing in the study of both the peak period and the off-peak period operation of the ASCT. Performance measures like number of stops, average approach delay, etc., will be used for a before/after comparison. In addition, impacts on the pedestrians will be assessed for pedestrian heavy signals.
- Operational Efficiencies during Anomalous Situations – The ASCT should not only be able to perform better during normal conditions but also should align itself so as to provide maximum capacity under anomalous conditions. Anomalous conditions for the Dodge Street will be poor weather (snow days), traffic incidents, preemptions of traffic, and handling of the Bus Rapid Transit.
- Performance during Over-saturation – Apart from these, the performance of the ASCT during the over-saturation is a major concern. It has been seen occasionally that ASCT fails under over-saturated conditions. Hence, the performance of the ASCT under over-saturation will also be evaluated. Usually, over-saturated conditions occur during morning peak hours when the office going traffic are trying to enter the network. Measures such as number of cycle failures, time to return to normal, etc. will be used to evaluate before/after conditions.
- Safety Concerns – ASCT has seen to reduce the number of crashes in the past. It will be difficult to assess the impact on crashes as crash history takes time to develop. Instead, camera feeds will be used to evaluate the most common types of conflict observed at each of the intersections. This will be done by observing multiple hours of clips for each approach for each intersection. In addition, special observation will be made for the intersections where the flashing yellow arrow is being implemented.