Graphical Performance Measures for Practitioners to Triage Split Failure Trouble Calls

Abstract

Overview of Study LocationThe location used to demonstrate the use of the Abstract Graphical Performance Measures for Practitioners to Triage Split Failure Trouble CallsDetector occupancy is commonly used to measure traffic signal performance. Despite improvements in controller computational power, there have been relatively few innovations in occupancy-based performance measures or integration with other data. This paper introduces and demonstrates the use of graphical performance measures based on detector occupancy ratios to verify potential split failures and other signal timing shortcomings reported to practitioners by the public. The proposed performance measures combine detector occupancy during the green phase, detector occupancy during the first five seconds of the red phase, and phase termination cause (gap out or force off). These are summarized by time of day to indicate whether the phase is undersaturated, nearly saturated, or oversaturated. These graphical performance measures and related quantitative summaries provide a first-level screening and triaging tool for practitioners to assess user concerns regarding whether sufficient green times are being provided to avoid split failures. They can also provide outcome-based feedback to staff after making split adjustments to determine whether operation improved or worsened. The paper concludes by demonstrating how the information was used to make an operational decision to re-allocate green time that reduced the number of oversaturated cycles on minor movements from 304 to 222 during a Thursday 0900-1500 timing plan and from 240 to 180 during a Friday 0900-1500 timing plan.

Developing the Collision Diagram Builder: Phase II Corridor Edition

“…A common occurrence at over-capacity signalized intersections are split failures. A split failure is when a movement (phase) at an intersection does not have enough green time (capacity) to serve the number of vehicles (demand) for that movement (Freije et al, 2014). Traditional in-pavement and pole-mounted sensors are limited in the quality of data provided; occupancy, count, and speed can be determined, but assessing queue length, the number of split failures per vehicle, delay, headway/gaps between vehicles, and travel time are difficult or approximated.…”

Integrating Traffic Signal Performance Measures into Agency Business Processes

“…Such performance measures have been the subject of considerable research in the past decade or so [2,[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. These are performance measures that focus on directly measuring the outcomes of system investments, in contrast to the more readily available investment-or input-oriented performance measures that quantify money or resource spent, rather than the outcome.…”

“…In addition, there are other means of logging similar data for other controller types, such as external data collection units [25,26]. The ability of such data to monitor operations in great detail, and to improve operations, has been very extensively documented [2,[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23].…”

“…This is a typical INDOT configuration. For these phases, we can use the volume-to-capacity (v/c) ratio based on the counts from the setback detectors [21]. Another way of viewing the same data is with a cumulative frequency diagram of the v/c ratio, as shown in Figure 5.15.…”

“…A combination of a green phase exceeding a certain occupancy ratio followed by a red phase exceeding a certain occupancy ratio triggers the indication. Typically, a threshold occupancy of 80% for the entire duration of the green phase and 80% for the first 5 seconds of the red phase is used [21].…”