Peter Koonce

Arterial Performance Measures with Media Access Control Readers: Portland, Oregon, Pilot Study

This study reports on the use of media access control (MAC) readers through the Bluetooth protocol by means of off-the-shelf equipment to measure arterial travel performance (segment travel time, average running speed, and origin–destination). First, the MAC reader technology was deployed at the same time that travel time runs by the traditional floating-car method were used to evaluate the general reliability and accuracy of the MAC technology. Second, the MAC reader technology was used to track before-and-after changes to signal timing along the corridor to measure the effectiveness of the adjustments, proving its real-world applicability while requiring far fewer resources than traditional data collection means. A comparison of the Bluetooth MAC address data with traditional Global Positioning System floating-car studies suggests that the larger data set from the Bluetooth data more effectively captures performance characteristics of the arterial. The research was conducted on a 2.5-mi suburban signalized arterial in Portland, Oregon, over 27 days. The paper concludes by discussing the system architecture for a permanent real-time deployment and other areas for future research. The real-time MAC reader information provides substantial opportunity to add new control and performance monitoring capability to other intelligent transportation system components, such as ramp metering, transit signal priority systems, and adaptive signal control.

EVALUATION OF DIAMOND INTERCHANGE SIGNAL CONTROLLER SETTINGS BY USING HARDWARE-IN-THE-LOOP SIMULATION

Research sponsored by the Texas A&M University ITS Research Center of Excellence was used to analyze the application of hardware-in-the-loop simulation at a diamond interchange. The study shows that hardware-in-the-loop simulation can improve the accuracy of traffic operations analysis by removing the inherent differences between emulated controllers and the actual hardware. In this study, a controller enhancement called conditional service was considered for implementation at an actuated diamond interchange. An evaluation of the traffic operations at the diamond interchange was completed using PASSER III-98, CORSIM, and hardware-in-the-loop simulation. The results of these analyses were compared to field observations that were used as the basis for evaluating the accuracy of each of these methods. An assessment of each method was discussed to identify issues and results using each method. One of the important supplementary benefits of hardware-in-the-loop simulation is that it allows engineers and technicians to test signal control strategies and hardware before deployment in the field. This capability provides a platform for innovation and the development of new control strategies. Hardware-in-the-loop simulation is also a valuable training tool.

DETECTION RANGE SETTING METHODOLOGY FOR SIGNAL PRIORITY

In urban areas, traffic signals often cause significant amount of delays to transit vehicles. The article discusses the potential to reduce control delay caused by traffic signals by implementing signal priority. Engineering studies are necessary to address both traffic and transit signal operations before the systems can be implemented. A comprehensive program requires coordination between the transit agency and the applicable transportation department to address needs of both agencies and users. The article details the efforts of the City of Portland and the Tri-County Metropolitan Transportation District of Oregon as well as the methodology for signal timing and detection distance setting.

Statistical Study of the Impact of Adaptive Traffic Signal Control on Traffic and Transit Performance

The Sydney Coordinated Adaptive Traffic System (SCATS) is designed to improve mobility on congested corridors with variable demand; SCATS is expected to improve transit performance. Because many urban corridors are heavily used by transit routes, it is important to determine how SCATS affects transit performance on congested corridors. However, there is limited research on evaluating the impact of SCATS on transit performance. To the best of the authors’ knowledge, this research presents the first field evaluation of SCATS with transit signal priority in the United States. The case study is based on before-and-after traffic and transit data along Powell Boulevard, one of the most congested urban arterials in the Portland, Oregon, metropolitan region. Using permanent traffic data collection stations, bus automated vehicle location and automatic passenger count data, and transit signal priority request data, this work presents the results of statistical tests and regressions to determine the impacts of SCATS. Statistically significant differences were observed in travel times and SCATS-related regression parameters. Overall, travel time changes or improvements related to SCATS seemed to depend greatly on the direction of travel and time of day.

An Evaluation of Comprehensive Transit Improvements—TriMet’s Streamline Program

Transit performance is influenced by a variety of factors in an urban environment. Making transit more convenient and competitive with automobile travel is a key objective for the Tri-County Metropolitan Transportation District of Oregon (TriMet). TriMet’s goal is to have a “Total Transit System” that makes transit an attractive choice for riders. Portland’s Streamline program has been a significant effort toward meeting these goals. The program has resulted in operating and capital cost savings for TriMet by delaying the need to add more buses to the fleet as well as operating savings due to reductions in running time variability. Further, the way the program was implemented resulted in a greater increase in ridership than would have been achieved had the service increases been spread more evenly around the system, confirming that the BRT approach serves transit agencies effectively by concentrating improvements on corridors.

Leading Pedestrian Intervals Treating the Decision to Implement as a Marginal Benefit-Cost Problem

To improve the safety of people walking at particular signalized intersections, traffic signal engineers may implement leading pedestrian intervals (LPIs) to provide pedestrians with a walk signal for a few seconds before the parallel vehicular green indication. Previous before-and-after studies and simple economic analyses have indicated that LPIs are low-cost tools that can reduce vehicle–pedestrian conflicts and crashes at some signalized intersections. Despite this evidence, municipalities have little guidance for when to implement LPIs. A marginal benefit–cost framework is developed with quantitative metrics and extends the concept of traffic conflicts and marginal safety–delay trade-offs to analyze the appropriateness of implementing an LPI at specific signalized intersections. The method provides guidance to help quantify the probability of a conflict occurring and direction on whether to implement an LPI at a given location from macroscopic-level inputs, including number of turning movements, crash data, and geometry. A case study with sample data indicated that an LPI was cost-effective for the scenario presented.

Evaluating Transit Priority Signal Phasing at Most Multimodal Intersection in Portland, Oregon

This research documents the operational benefits of additional phases, barrier bars, and a call-based transit priority signal-phasing strategy over a more traditional eight-phase, two-barrier preemption-based transit signal–phasing strategy. The call-based timing strategy, with a more flexible ring-and-barrier structure, takes advantage of additional phases to run less-impactful transit prioritization for light-rail trains. These two strategies have been field implemented in Portland, Oregon, at the signalized intersection of Southwest Porter Street and Southwest Moody Avenue, an intersection that has distinct signalized movements for the private-automobile, streetcar, light-rail train, bus, pedestrian, and bicycle modes. The operations of the two-intersection signal-phasing strategies were evaluated and tested by using hardware and software-in-the-loop microsimulation (in Vissim) to isolate the expected change in operational efficiency in modal delay. The two-barrier preemption-based transit signal-phasing strategy showed high variability in delay for certain movements, in particular, pedestrians. The call-based phasing strategy with flexible ring-and-barrier structure reduced total and average intersection delay. This research shows that the call-based phasing strategy with flexible ring-and-barrier structure can provide a less disruptive transit prioritization. Agencies should consider the call-phased transit priority strategy over the more traditional preemption-based strategy at a signalized intersection when (a) delaying potential preemptive movements mode will not have large safety effects, (b) pedestrian demand is high, (c) preemption service will be frequent, or (d) the intersection is operating at or over capacity.

Assessment of Bicyclist Behavior at Traffic Signals with a Detector Confirmation Feedback Device

Bicycling has been increasing in North America, and intersections have been modified to accommodate the increase in cyclists. However, the increase in cycling is outpacing the supply of high-quality cycling markings, signing, signals, and general infrastructure at intersections. For example, recent research indicates that more than 50% of bicyclists do not understand that the 9C-7 bicycle stencil symbol from the Manual on Uniform Traffic Control Devices (MUTCD) indicates the optimal waiting position for a cyclist to call a green light. Subsequently, people on bicycles may run red lights because they do not understand how the MUTCD 9C-7 pavement marking works. This infrastructure shortcoming illustrates the need to study how new roadway information may affect user behavior and traffic signal compliance. This research documents the effects of an active feedback device on cyclist behavior in an effort to improve the cycling experience. A blue light feedback device was installed at a signalized intersection approach, and its impact on bicyclist behavior was studied. A statistically significant increase in the number of bicyclists who used the MUTCD 9C-7 marking (instead of the existing bicycle push button) occurred after installation of the blue light feedback device and especially after a sandwich board sign was installed that described the purpose of the blue light. These results indicate that a blue light feedback device (accompanied with bicycle detection and the standard marking) could be used effectively in lieu of bicycle push buttons. Also, the effect of the blue light feedback device on bicyclist compliance with traffic signals (red light runners) was negligible.

A Method to Verify Railroad Interconnect With Highway Traffic Signal Systems

In response to increasing concern about railroad grade crossing safety, the Federal Railroad Administration and Department of Transportation issued Safety Advisory 2010-02 recommending in part “...that railroads conduct comprehensive joint inspections of highway traffic signal pre-emption interconnection with State and local highway authorities...” 2010-02 also recommends recording devices at interconnected highway-rail grade crossings.This paper addresses a method to facilitate these goals by enabling the highway authority to independently verify that rail equipment is functioning properly, and just as importantly, enabling the railroad to independently verify that the highway traffic signal equipment is providing adequate clearance time in advance of the arrival of the train in the crossing. The method involves adding two circuits between the rail equipment and the traffic signal equipment: a crossing island circuit, and a start of the traffic clearance phase indicator from the traffic signal to the rail equipment. This system has been implemented at two intersections in Portland, Oregon, with plans for further implementation.Copyright

Mitigating Right-Turn Conflict with Protected Yet Concurrent Phasing for Cycle Track and Pedestrian Crossings

Where there are high turn volumes or speeds, pedestrian and bicycle crossings may need to be protected from right turns as well as left turns. Cycle tracks may need protected crossings even where right-turn volumes are modest. This research explores a phasing scheme in which right turns have their own phase and bike and pedestrian crossings run in their own distinct phase concurrent with the parallel vehicular through phase. This protected yet concurrent phasing scheme is more efficient than an all-pedestrian phase. A general framework for sequencing phases accounting for the right turn and crossing conflict is shown with four rings instead of the usual two. Seven examples of protected yet concurrent phasing from the United States and the Netherlands illustrate the scheme and characterize its likely impacts in terms of delay and street footprint. Overall delay and footprint impacts are found to be modest; factors that affect the impact of protected phasing include complexity of the phasing plan, coordination, and the possibility of using reservice. Because protected yet concurrent phasing makes efficient use of time, this phasing is also economical with space. Although the phasing requires right-turn lanes, its use can reduce the necessary number of through lanes, especially in comparison with all-pedestrian phasing.