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Indianapolis, IN, United States

Brennan Jr. T.M.,Purdue University | Day C.M.,Purdue University | Sturdevant J.R.,100 North Senate Avenue | Raamot E.M.,Econolite Control Products Inc. | Bullock D.M.,Purdue University
Transportation Research Record | Year: 2010

Track clearance green phases are used at railroad-preempted intersections to provide time to clear the railroad tracks of highway vehicles before a train arrives. This paper outlines performance measures based on high-resolution, real-time traffic signal event data that can be used to assess the maximum right-of-way transfer time to track clearance green phases as well as the synchronization of the track clearance phase with the railroad gate warning system located at the crossing. These performance measures were applied to a railroad-preempted intersection over a 13-month period. Right-of-way transfer times from more than 5,002 preemption events demonstrate the importance of using automated methods for validating design assumptions for right-of-way transfer time made by traffic engineers. Track clearance performance measures tabulated over 7,648 preemptions demonstrate the need for using a longer fixed, worst-case green time for track clearance or an extensible track clearance interval that terminates when the gates descend. The parameter description on how to get gate descent information can be inferred from either the active warning-time (flashing-light signals) activation or a separate gate-down circuit. The paper concludes with recommendations for incorporating these performance measures in traffic controller firmware to address recommendations proposed in 1996 by the National Transportation Safety Board after the Fox River Grove, Illinois, railroad-grade crossing crash in 1995. Source


Day C.M.,Purdue University | Premachandra H.,Purdue University | Brennan Jr. T.M.,Purdue University | Sturdevant J.R.,100 North Senate Avenue | Bullock D.M.,Purdue University
Transportation Research Record | Year: 2010

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. Source


Day C.M.,Purdue University | Sturdevant J.R.,100 North Senate Avenue | Bullock D.M.,Purdue University
Transportation Research Record | Year: 2010

The design of traffic signal timing plans is typically based on a single day of manual turning movement counts. Once systems are constructed and settings are implemented, they receive maintenance on fixed schedules of a number of years. Public feedback (e.g., phone calls) is in many cases the primary channel by which an agency obtains feedback about the system. System assessment is often conducted by collecting a new small data sample and repeating the design process. One common and frustrating result is that the same settings are frequently recommended by the design software even when problems are known to exist. This paper illustrates how fundamental traffic engineering concepts can be integrated with traffic signal system detection and controller status information to provide outcome-based measures of arterial-system performance. These outcomebased measures of performance characterize the operation of a signal system and provide a data set that can be used to identify and prioritize opportunities for operational improvements in the system. A consistent set of performance measures used across a signal network would affect traffic signal operations at two distinct levels. At the regional or district level, it would provide a continuously updated list of problem areas with greater accuracy than telephone reports. At the agency jurisdiction level, it would provide quantitative data for prioritizing resources across multiple districts and by time of day. Source


Day C.M.,Purdue University | Haseman R.,Purdue University | Premachandra H.,Purdue University | Brennan Jr. T.M.,Purdue University | And 3 more authors.
Transportation Research Record | Year: 2010

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 offset-tuning 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. Source


Brennan Jr. T.M.,Purdue University | Hulme E.A.,Purdue University | Day C.M.,Purdue University | Sturdevant J.R.,100 North Senate Avenue | And 3 more authors.
Transportation Research Record | Year: 2010

The Manual on Uniform Traffic Control Devices provides a list of factors to be considered when an agency is determining whether a highway-railroad crossing located farther than 200 ft from a signalized intersection should have a railroad-preempted interconnection or be provided with alternative queue management methods. One such factor is the estimated queue length between the signalized intersection and the railroad crossing. Currently, no systematic assessment procedure both (a) quantitatively prioritizes intersections near railroad crossings on the basis of their potential to queue vehicles over the tracks and (b) is reasonably quick to apply agencywide. This paper proposes a decision tree procedure for screening and prioritizing traffic signals near highway-railroad crossings on the basis of estimated queue lengths. An integral component of this procedure is the concept of queue margin, calculated as the difference between (a) clear storage distance between the track and the stop bar and (b) the estimated length of queue traffic. This prioritization procedure was applied to 595 traffic signals in northwest Indiana to prioritize and rank the top 20 intersections for more detailed site investigation. Example intersections are used to illustrate higher-fidelity data collection and queue management strategies. Source

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