Using traffic signal control to better serve pedestrians and limit speeding on urban arterials: adaptive walk intervals and speeding opportunities.
Permanent URL:
http://hdl.handle.net/2047/D20292647
Koutsopoulos, Haris (Committee member)
Wang, Qi (Committee member)
Dulaski, Daniel (Committee member)
First research (chapter 2), introduces a novel concept of an adaptive walk interval. The idea is to use information from the recently passed signal cycles to predict the length of next parent phase, and then to set the walk interval length to fit within that parent phase with only a small chance of forcing the parent phase to run longer. Two methods of predicting the length of the parent phase are proposed, ratio estimation and stratification. The methods were tested in simulation with coordinated-actuated and fully actuated control, with and without pedestrian recall, and with and without permissive windows. The results show that with almost no impact on vehicular delay and without requiring any expensive equipment, adaptive walk intervals can significantly decrease pedestrian delay.
Second research (chapter 3), explores the ways that traffic signal coordination creates or limits speeding opportunities on bidirectional arterials. Two measures of speeding opportunity are proposed. The first measure is number of unconstrained vehicles, meaning all vehicles arriving at a stopline on green and with no vehicle less than 5 s ahead of them. The second measure is the number of speeders in a traffic microsimulation in which 20 percent of the vehicles have been assigned a desired speed in the speeding range. Theoretical analysis, ii confirmed by two case studies, show how speeding opportunities are related to cycle length, specified progression speed (as in input to signal timing software), intersection spacing, degree of saturation, and recall settings. The key role of clusters of intersections with near-simultaneous greens, a byproduct of bi-directional coordination with short intersection spacing, is studied. It is shown that clusters with many intersections create a strong speeding incentive. Also, by reducing the cycle length and progression speed, the cluster size can be reduced. The impact of changes in progression speed tends to be stepped, meaning that they make a difference only when the change in progression speed is enough to alter cluster size. A case study also shows that dividing an arterial into smaller coordination zones, with each zone having its own cycle length, can substantially reduce speeding opportunities with little or no increase in vehicular delay, mainly due to lowering cycle length.
Third research (chapter 3), explores empirical data of traffic signal control and traffic flow on excessive speeding at signalized intersections in urban arterials A logit regression is applied to estimate the risk of a vehicle being an excessive speeder passing through a signalized intersection. Drivers are classified into Speeder and non-Speeder groups. The experienced traffic flow condition and signal status by each driver is investigated. The modeling results revealed that the risk of speeding increases with elapsed green time and doubles with long headway (>5). The risk of excessive speeding can be limited by using traffic signal control to reduce the number of vehicles pass with long headway after green start.
pedestrian
speed control
speeding
traffic signal control
traffic simulation
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