Thomas M Brennan Jr

Evaluation of Arterial Signal Coordination: Methodologies for Visualizing High-Resolution Event Data and Measuring Travel Time

Signal offsets are a signal-timing parameter that has a substantial impact on arterial travel times. The traditional technique is to optimize offsets with an offline software package, implement the settings, and then possibly observe field operations. It is not uncommon for a traffic engineer to fine-tune the settings by observing the arrivals of platoons at an intersection and making adjustments to the offset from this qualitative visual analysis. This paper discusses two tools to assist the engineer in managing arterial offsets. First, it introduces the Purdue coordination diagram (PCD) as a means of visualizing a large amount of controller and detector event data to allow investigation of the time-varying arrival patterns of coordinated movements. The second technique is arterial travel time measurement by vehicle reidentification via address matching by Bluetooth media access control. This technique is used to evaluate existing offsets and assess the impact of implemented offset changes. These tools are demonstrated with a case study involving a before-and-after comparison of an offsettuning project. PCDs were used to identify causes of poor progression in the before case, as well as to visualize both the predicted and the actual arrival patterns associated with the optimized offsets. More than 300 travel time measurements from Bluetooth probes were used for statistical assessment of before-and-after travel time. The statistical comparison showed a significant (at the 99% level) 1.7-min reduction (28%) in mean northbound travel time, corresponding to a 1.9-min reduction in median northbound travel time. Southbound travel times were not negatively affected by the offset changes.

Operational Evaluation of Wireless Magnetometer Vehicle Detectors at Signalized Intersection

Compact wireless magnetometers offer attractive vehicle detection ability at signalized intersections because their installation requires minimal pavement cutting and the detectors are less likely than saw-cut inductive loops to malfunction because of pavement failure. A study was done at an instrumented intersection to evaluate the performance of wireless magnetometers at operating signalized intersections. A test bed was constructed with colocated inductive loop and wireless magnetometer detection zones. A 5-day analysis period was conducted for each of two left-turn pockets at an actuated, coordinated signalized intersection. Discrepancies between the detection and nondetection states were quantified with highresolution log data of traffic events, and 240 h of data collection that was ground-truthed by visual inspection of video recordings of the detection zones. Behavior of detector state changes was also characterized. Wireless magnetometers were found to perform similarly to loops in relation to missed calls and had a slightly higher tendency to generate false detection calls. Detection state changes in the wireless magnetometers had typical (85th percentile) reporting latencies of 0.2 s or less for activation and 0.5 s or less for state termination. The paper concludes by recommending 8-ft spacing of the sensors adjacent to the stop bar to minimize missed calls.

Reliability, Flexibility, and Environmental Impact of Alternative Objective Functions for Arterial Offset Optimization

A wide variety of alternative optimization objective functions, such as minimizing stops, minimizing delay, and maximizing arrivals on green, has been reported in the literature. An extensive literature evaluates these alternative objective functions with models. This paper reports on the field deployment of these alternative optimization functions, developed with high resolution controller data, to adjust offsets on an arterial system of eight coordinated signals. The deployment consisted of a 1-week base data collection and four 1-week deployments of offset plans developed with four alternative optimization objective functions. Travel times of anonymous probe vehicles were measured during the study period to evaluate the impact of these alternative optimization functions on corridor travel time. All objective functions were successful in reducing median corridor travel time significantly. Median travel time decreased by more than 1 min in both directions on the 5-mi corridor. Travel time reliability, as quantified by the difference between 75th and 25th percentile travel times, was improved for the busiest portion of the day. A lower bound of the estimated annual savings on user costs was

Visual Education Tools to Illustrate Coordinated System Operation

472,817, with an associated reduction in carbon dioxide emissions of 197 tons per year.

Reliability, Flexibility, and Environmental Impact of Alternative Arterial Offset Optimization Objective Functions

The configuration of a single controller in a coordinated arterial signal system requires the programming of approximately 250 parameters ranging from minimum green times to complex hardware-specific settings that determine how unused green time is allocated to competing phases. When this parameter count is extrapolated to a 10-intersection arterial (2,500 parameters), one or more data entry errors are likely to occur and must be identified and corrected. Ensuring that the resulting coordinated signal system operates as designed requires an exceptionally high level of expertise to confirm by visual field observations and a perhaps unattainable level of expertise in verification by inspection of data entry screens in an office. There is a clear need for visualization tools to provide educational insight into how coordinated signal systems should be expected to operate under different parameter settings and to document coordinated system behavior. In this paper a series of graphics was developed to visualize coordinated system operation characteristics such as time-of-day schedule change time, observed cycle length, green time and split time, coordinated phase actuation, early return to green, arrivals over advance detection relative to green indication, progression quality characteristics related to offset, adjacent signal synchronization, coordinated phase operation in rest, plan time changes, preemption, impact of queuing, and longitudinal analysis of splits. These graphics can be used as a new learning tool, as well as a visual feedback tool to confirm that a coordinated system is operating as expected.

Spatially Referenced Probe Data Performance Measures for Infrastructure Investment Decision Makers

A wide variety of alternative optimization objective functions have been reported in the literature such as minimizing stops, minimizing delay, and maximizing arrivals on green. There is extensive literature evaluating these alternative objective functions using models. This paper reports on the field deployment of these alternative optimization functions, developed using high resolution controller data, to adjust offsets on an arterial system of eight coordinated signals. The deployment consisted of a one-week base data collection, and four one-week deployments of offset plans developed using four alternative optimization objective functions. Anonymous probe vehicle travel times were measured during the study period to evaluate the impact of these alternative optimization functions on corridor travel time. All of the objective functions were successful in significantly reducing median corridor travel time. Median travel time decreased by more than one minute in both directions on the 5-mile corridor. Travel time reliability, as quantified by the difference between 75 th and 25 th percentile travel times, was improved for the busiest portion of the day. A lower bound on the estimated annual user cost savings was estimated at

Probe Vehicle-Based Statewide Mobility Performance Measures for Decision Makers

472,817 with an associated reduction in CO 2 emissions of 197 tons per year.

Roadway System Assessment Using Bluetooth-Based Automatic Vehicle Identification Travel Time Data

Moving Ahead for Progress in the 21st Century, the recently enacted highway bill, challenges transportation professionals to develop a comprehensive set of performance measures for managing most aspects of the transportation system. Historically, performance metrics have been created on an agency-by-agency basis with little consistency between data collection frequency and quality. In recent years, crowdsourced data have become a high -fidelity data source that could be used to develop spatially oriented performance measures that could scale nationwide. This paper summarizes the rapidly evolving literature on probe vehicle data and proposes a series of performance measures to characterize the temporal and spatial aspects of congestion in a graphical manner that decision makers may use to evaluate the impact of past investments and prioritize future investments. The I-80-I-94 corridor in northwest Indiana, near Chicago, Illinois, is used to present the methodologies. The paper concludes with a discussion of how these techniques can be extended on a national scale to characterize corridors such as I-80 from New York to California.

Performance Measures to Characterize Corridor Travel Time Delay Based on Probe Vehicle Data

Decision makers in state transportation agencies typically manage budgets approaching or exceeding

2012 Indiana Mobility Report: Full Version

1 billion. Historically, the data used to make investment decisions have been quite coarse and have been typically based on short-term volume counts fed into models to forecast performance. As a result, it is not uncommon for construction projects to address needs that were forecast to be a priority 5 to 10 years earlier, while more pressing congestion challenges go unmet. It is essential that long-term planning begins to be supplemented by more current performance measures. The emerging private-sector probe vehicle data obtained from commercial providers offer an opportunity to augment traditional forward-looking planning models with performance measures that reflect the conditions motorists are experiencing today. This paper proposes scalable, analytical probe data–reduction techniques to create technically sound, yet visually intuitive, system-performance measures of current freeway conditions. These types of performance measure are increasingly used by high-level agency management to identify locations at which customers experience congestion, and the magnitude of that congestion, and to compare congestion on various highway corridors. These proposed performance measures can be used for policy-oriented decisions, such as the prioritization of capital program investments, the management of snow removal, and the scheduling of lane closures. The techniques are applied to seven Indiana Interstate highways, comprised of 1,886 directional miles. The Interstates span rural and urban sections that experience varying levels of recurring and nonrecurring congestion as a result of winter weather and construction activity. Specific examples adjacent to the Indianapolis, Indiana; Louisville, Kentucky; and Chicago, Illinois, metropolitan areas are presented, along with the 10 most congested Interstate segments.