Performance-Based Management of Traffic Signals (2020) / Chapter Skim
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CHAPTER FOCUS After an agency has procured and installed the necessary resources to deploy signal performance measures (as described in Chapter 4) , they must program the intersections into the automated traffic signal performance measure (ATSPM)
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EXHIBIT 5-1. INTERSECTION CONFIGURATION REQUIREMENTS INTERSECTION CONFIGURATION REQUIREMENTS DESCRIPTION/EXAMPLES Signal ID • Number (e.g., IP address)
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5.2.2 TIMESTAMPS POTENTIAL ISSUE Data are not being reported at the correct times. POTENTIAL CAUSE • Enumerations timestamped using Coordinated Universal Time (UTC)
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5.2.3 INTERSECTION CONFIGURATION POTENTIAL ISSUE Data are being reported from a different intersection than intended. If a signal ID is mis-programmed, data from an intersection may be tied to the wrong intersection name or detector configuration.
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Lane 1 Lane 2 Lane 3 5.2.4 DETECTOR CONFIGURATION POTENTIAL ISSUE Volumes are reported higher or lower than expected conditions based on directionality, peak periods, or values compared to capacity. POTENTIAL CAUSE • Mis-programmed signal ID.
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5.3 DATA VERIFICATION Although data can be verified qualitatively based on knowledge of the intersection, highresolution data should also be verified quantitatively using a secondary source. 5.3.1 TRAFFIC COUNTS DESCRIPTION Traffic counts can be collected using a traditional method, such as permanent count stations or manual turning movement counts, and then compared against detector actuations from high-resolution data.
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Track Detector Occupancy Using Video Track Signal Display Outputs Using Video 5.3.2 VIDEO RECORDING DESCRIPTION Video recordings can be used to verify any signal performance measure. Agencies can directly compare events recorded by the controller and events seen on the video for a selected time period.
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Lower Midday Speeds EXHIBIT 5-11.
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5.4 VALIDATION ATSPMs allow an agency to collect robust and widespread signal performance data, which can help practitioners (1) find problems faster (e.g., mis-programmed parameters, malfunctioning equipment, and intersections that need to be retimed)
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5.5 INTERSECTION/UNCOORDINATED TIMING VALIDATION Intersection/uncoordinated timing parameters must be programmed at every signalized intersection. 5.5.1 YELLOW CHANGE DESCRIPTION The Manual on Uniform Traffic Control Devices (MUTCD)
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5.5.2 RED CLEARANCE DESCRIPTION Red clearance is a signal timing parameter that is applied differently across agencies. While not required, the purpose is to provide an interval when conflicting signal displays are red so that a vehicle that entered the intersection on yellow has enough time to cross the intersection without conflict.
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5.5.3 MINIMUM GREEN DESCRIPTION Minimum green values should be set based on driver expectancy and to clear vehicle queues (depending on the detector configuration) , but values should also consider other intersection users including pedestrians and roadway users with longer start-up times (i.e., bicycles, trucks, and transit)
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5.5.4 MAXIMUM GREEN DESCRIPTION Maximum green is the longest duration a green signal indication can be displayed in the presence of conflicting demand. If it is too short, vehicles will remain unserved at the end of green.
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5.5.5 PASSAGE TIME DESCRIPTION Passage time (also known as unit extension or gap time) is a parameter that is used to terminate the current phase when a gap in traffic is identified based on a particular flow rate.
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5.5.6 PEDESTRIAN INTERVALS DESCRIPTION The pedestrian phase consists of the Walk, Flashing Don't Walk, and Steady Don't Walk intervals. While the Manual on Uniform Traffic Control Devices (MUTCD)
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5.5.7 RECALLS DESCRIPTION Recalls place a call automatically for a specified phase regardless of any detector actuations (except for soft recall which only places a call in the absence of calls on other phases)
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Phases 2 and 6 Gapping Out During the Night After Recall Adjustment (B) After recall setting adjustment Phases 2 and 6 Maxing Out During the Night Because of Maximum Recall (A)
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5.5.8 TIME-OF-DAY (TOD) PLANS DESCRIPTION Time-of-day plans allow a controller to apply different signal timing parameter values during different times of day or days of the week.
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5.6 SYSTEM/COORDINATED TIMING VALIDATION System/coordinated signal timing parameters include cycle lengths, splits, and offsets that are used to progress vehicles. 5.6.1 CYCLE LENGTH DESCRIPTION Cycle length is the time required for a complete sequence of signal phases at an intersection.
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EXAMPLE EXHIBIT 5-22 shows green and red occupancy ratios at an intersection before and after split adjustments. If the green and red occupancy ratios are both above 80%, the cycle is logged as having a split failure.
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5.6.3 OFFSETS DESCRIPTION Offsets define the time relationship between the "system" clock and the "local" clock at individual intersections, thereby controlling the time relationship between intersections based on the actual or desired travel speed. Ideally, they allow platoons of vehicles to arrive on green (i.e., leave an upstream intersection at the start of green and arrive at a downstream intersection at the start of green)
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Most Vehicles Arriving on Red Before Offset Adjustment (A) Before offset optimization Most Vehicles Arriving on Green After Offset Adjustment (B)
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5.7 ADVANCED SYSTEMS AND APPLICATIONS VALIDATION Advanced systems are often implemented to address unpredictable traffic conditions. Objectives for these systems will vary based on agency needs.
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5.7.2 PREFERENTIAL TREATMENT (PREEMPTION AND PRIORITY) DESCRIPTION Practitioners can use preferential treatment to alter normal operations for a preferred vehicle.
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5.8 EQUIPMENT MAINTENANCE VALIDATION This section discusses performance measures related to the maintenance of traffic signal equipment. 5.8.1 COMMUNICATION DESCRIPTION Communication is critical to a scalable monitoring system as well as keeping intersections coordinated.
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5.8.3 VEHICLE DETECTION DESCRIPTION Although controllers sometimes log detector failures as alarms, practitioners can also use phase termination information and vehicle volumes to identify detector failures. If phases are consistently maxing out during low-volume periods (e.g., late at night)
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5.8.4 PEDESTRIAN DETECTION DESCRIPTION Practitioners can use performance measures to identify locations with malfunctioning pedestrian detection. The phase termination and pedestrian delay metrics report pedestrian actuations.
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Total AOG Downstream AOG Upstream AOG EXHIBIT 5-30.
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5.11 AGGREGATED REPORTS As of writing, aggregated reports are being incorporated into the open source code and several vendor products. Aggregated reports provide several benefits for signal timers and other stakeholders.
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5.11.2 DASHBOARDS Dashboards can be used to compare current conditions to historical data. This type of summary is useful for both signal timers and decision-makers to track progress.
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5.11.3 SUMMARY TABLES AND CHARTS Summary tables and charts aggregate data up to a high level so that performance measures can be shared with the public and decision-makers. It is most useful to report performance measures against EXHIBIT 5-35.
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5.12 REFERENCES 1. Bullock, D
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