Managing User Delay with a Focus on Pedestrian Operations
Christopher Sobie, Lee Engineering, LLCShow Abstract
Edward Smaglik, Northern Arizona University
Anuj Sharma, Iowa State University
Andy Kading, Portland State University
Sirisha Kothuri, Portland State University
Peter Koonce, City of Portland, Oregon
Across the U.S, walking trips are increasing. However, pedestrians still face significantly higher delays than motor vehicles at signalized intersections due to traditional signal timing practices of prioritizing vehicular movements. This study explores pedestrian delay reduction methods via development of a pedestrian priority algorithm that selects an operational plan favorable to pedestrian service, provided a user defined volume threshold has been met for the major street. This algorithm, along with several operational scenarios, were analyzed with VISSIM using Software-In-The-Loop (SITL) simulation to determine the impact these strategies have on user delays. One of the operational scenarios examined was that of actuating a portion of the coordinated phase, or actuated-coordinated operation. Following a discussion on platoon dispersion and the application of it in the design of actuated-coordinated signal timing parameters, a sensitivity analysis was performed on vehicle extension timers to explore the impact that this coordinated movement parameter has on user delay. In the scenario analysis, it was shown that employing fully actuated (also known as Free) operation, either with the designed algorithm or without was an effective method of reducing minor street pedestrian delay while also decreasing average intersection vehicle delay for the volumes used in the simulation. The vehicle extension sensitivity analysis showed that shortening the extension timer of an actuated-coordinated phase can reduce the minor street pedestrian delay without increasing overall vehicle delay, which could be a tool used by agencies while in coordinated operation to prioritize pedestrians.
Optimal Cycle Length Formulas for Intersections with or without Transit Signal Priority
Bart Wolput, Katholieke Universiteit Leuven (KU Leuven)Show Abstract
Eleni Christofa, University of Massachusetts, Amherst
Chris Tampère, Katholieke Universiteit Leuven (KU Leuven)
Updating and optimizing signal timings have been proven to reduce delay at signalized intersections. The Webster formulas for optimal green split and cycle length estimation are a common way for optimizing signal settings at signalized intersections. However, these equations were intended to be used for optimizing signal timing plans for fixed-time isolated intersections, balancing phase utilization and minimizing car delay when no spillbacks are present. Therefore, these formulas are less appropriate for near-saturated conditions and transportation systems when transit signal priority (TSP) strategies are in place. The main objective of this paper is to develop formulas for the optimal cycle length estimation of isolated intersections that can be applied in practice when TSP is implemented and/or when the intersection operates under near or oversaturated conditions.
A linear regression formula for optimal cycle length is developed as a function of lost time and the intersection flow ratio. It appeared that for green split, no new regression formulas were required as the Webster proportional green split is near-optimal. The cycle length formula is validated for undersaturated, near-saturated and oversaturated conditions with and without transit signal priority for 2, 3 and 4 phase signalized intersections. Compared to Webster’s formula the proposed formula shows a significant improvement in reducing person delay. Compared to the Webster formula there is a 6%, 17% and 22% less average person delay and a 16%, 27% and 35% less average bus delay for 2, 3 and 4 phase signalized intersections respectively.
Predictive-Tentative Transit Signal Priority with Self-Organizing Traffic Signal Control
Bahman Moghimi, City College of New YorkShow Abstract
Peter Furth, Northeastern University
Burak Cesme, Kittelson & Associates, Inc. (KAI)
Reducing bus delay beyond what can be achieved with conventional transit signal priority requires making and responding to longer range predictions of bus arrival time which include dwell time at an upstream stop. At the same time, priority actions based on such uncertain predictions should be reversible if the dwell time turns out to be much longer than expected. Logic for making such longer-range and taking appropriate priority actions is proposed for application in the framework of self-organizing traffic signal control as described by Cesme and Furth. Predicted arrival time is based on a calculation of expected remaining dwell time and is compared with the earliest time the bus phase can be expected to return to green. One possible decision is to expedite return to green, meaning that secondary extensions (a feature of self-organizing control logic) are inhibited. The other is to hold the green; however, this decision can be reversed if updated predictions of expected remaining dwell time indicate that it will arrive after the maximum allowed green extension has expired. Tests on a corridor with 9 signalized intersections show a 75% reduction in bus delay, to only 5 s per intersection, with only a 3 percent increase in general traffic delay.
An Efficient Priotiy Control Model for Multi-Modal Traffic Signal
Mehdi Zamanipour, NRC Research AssociateshipShow Abstract
Larry Head, University of Arizona
Yiheng Feng, University of Arizona
Shayan Khoshmagham, ITERIS, Inc.
In this paper, a model for multi modal traffic signal priority control is presented. The approach is based on an analytical model and a flexible implementation algorithm that considers real-time vehicle actuation. The model considers the needs of different modes in a connected vehicle environment. It can be efficiently solved and implemented in real-time applications. The model provides an optimal signal schedule that minimizes the total weighted priority request delay. A flexible implementation algorithm is designed that guarantees the optimal signal schedule is applied with minimum negative impact on regular vehicles. The model has been tested in a simulation framework on two different networks: San Mateo, CA and Anthem, AZ. The simulation experiments show that the model, when compared to fully actuated control, is able to reduce average priority vehicle delay and travel times while it does not have significant negative impact on the passenger cars.