Alexander M. Hainen

Estimating Route Choice and Travel Time Reliability with Field Observations of Bluetooth Probe Vehicles

Route choice is often assessed with either a modeling technique or field observations. Field observations have historically used a variation of license plate matching. The proposed technique assesses route choice and travel time that uses an anonymous Bluetooth media access control (MAC) address sampling technique as a surrogate for license plate matching to assess route choice. The Bluetooth sampling technique was used to evaluate the impact of an unexpected bridge closure in northwest Indiana, including an assessment of the proportion of vehicles using each of four alternate routes. The Bluetooth technology also provided a means to collect travel time data for each alternate route; these observed travel times were also compared with travel time estimates obtained by route classification and link distance. In general, the route choice behavior was consistent with observed travel time estimates. The Bluetooth sampling technique is cost-effective to deploy, and although results are approximate, direct measurement of travel times and route choice is useful for public agencies to assess mobility and travel time reliability along alternate routes.

Performance Measures for Adaptive Signal Control: Case Study of System-in-the-Loop Simulation

The simulation of local signal controllers has become increasingly sophisticated in recent years and has been paralleled by improvements in the integration of adaptive systems into simulation. This paper describes and demonstrates an emerging methodology for the evaluation of adaptive signal control that is termed “system-in-the-loop simulation.” This methodology extends existing software-in-the-loop simulation by linking virtualized traffic controllers with real-world adaptive-control systems. In addition, the authors propose an analysis methodology that fuses data on simulated probe vehicles with data on high-resolution controller events. Through this data fusion, traditional measures of simulation performance such as delay can be enhanced with operational measures of performance that characterize quality of progression and capacity utilization. In addition, adaptive-control performance can be characterized in relation to overall impact on traveler delay and also described in terms that are meaningful for improvement of control schemes. An example case study is presented: the ACS-Lite adaptive system was tested on a 19-intersection system in Morgantown, West Virginia, under a special-event scenario. Free, fully actuated control was compared with traditional time-of-day and traffic-responsive control both with and without the use of the adaptive-control system ACS-Lite. Overall delay results are presented and contrasted with more detailed analysis of event-based performance measures at a single intersection and on a networkwide basis.

Performance Characterization of Arterial Traffic Flow with Probe Vehicle Data

Extensive literature in the adaptive control field uses local detection available from the traffic controller as input to various control models to adjust splits, cycle lengths, and offsets. All these models have implicit control objectives, which include facilitated progression, minimized stops, minimized delay, and equitable allocation of green time. Enormous opportunities exist to incorporate probe data into the decision process with respect to when and where adaptive control can be used and which operating objectives are most applicable to a corridor as well as to an outcome assessment tool to evaluate the effectiveness of adaptive control. The research reported in this paper compared how probe data sources could be used to identify appropriate adaptive control objectives and to assess the performance of adaptive systems. Four case studies demonstrated how travel time data could be used to evaluate existing conditions, to evaluate the outcome of a traditional signal retiming, and to assess the feasibility of adaptive control opportunities. Currently, the richest probe data sets are provided by agency-installed equipment. Given the increasing penetration of crowd-sourced probe data devices and the onset of connected vehicle infrastructure, however, these sources could provide similarly rich data. This paper recommends that commercial data providers begin to develop more detailed base maps. These maps would provide richer probe data information, such as hour-by-hour statistical distributions and approach delay for signalized arterials for which the segments did not span multiple intersections. This recommendation should motivate agencies to develop more detailed specifications for probe data that will better serve their needs.

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

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

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

Evaluation of Spatial and Temporal Speed Limit Compliance in Highway Work Zones

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

Graphical Performance Measures for Practitioners to Triage Split Failure Trouble Calls

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

Typically, speed limits are reduced in work zones to safely accommodate construction activities and motorists on the roadway. This paper presents a methodology to evaluate the temporal and spatial effects of techniques designed to encourage compliance with work zone speed limits. The evaluations were performed over short and long segments within and adjacent to an Interstate construction work zone in suburban Indianapolis, Indiana, with the use of vehicle probe data. Space mean speed was measured by using 13 Bluetooth probe data acquisition stations, which provided a random sample of unique identifiers for approximately 11% of the passing vehicles. These space mean speed data were used to compute a series of comparisons between a day with no enforcement activity and a day with exceptionally high enforcement. During enforcement, the space mean speed decreased by approximately 5 mph throughout the 12.2-mi study segment. Within 30 min after the enforcement detail ended, however, space mean speeds increased, and there was no statistically significant residual impact on the space mean speed. Even at the absolute peak of enforcement, 75% of the probe vehicles exceeded the speed limit in all but one of the segments that had a posted speed limit of 45 mph. In addition, 25% of the probe vehicles exceeded the posted limit by more than 5 mph in all 45-mph segments during peak enforcement. The study is perhaps the largest ever conducted with respect to concurrent enforcement and extensive space mean measurement. The data represent an upper bound on the impact of enforcement activity on work zone speeds and should be of interest to public agencies as they consider compliance techniques.

Probe vehicle data for characterizing road conditions associated with inclement weather to improve road maintenance decisions

Detector occupancy is commonly used to measure traffic signal performance. Despite improvements in controller computational power, there have been few innovations in occupancy-based performance measures and little 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 5 s of the red phase, and phase termination cause (gap out or force-off). They are summarized by time of day to indicate whether the phase is undersaturated, nearly saturated, or oversaturated. The graphical performance measures and related quantitative summaries provide a first-level screening and triaging tool to help practitioners assess user concerns about whether sufficient green times are being provided to avoid split failures. They can also provide outcome-based feedback to staff after split adjustments have been made to determine whether operation improved or worsened. The paper demonstrates how the information was used to make an operational decision to reallocate green time that reduced the number of oversaturated splits on minor movements from 304 to 222 during a Thursday 0900 to 1500 timing plan and from 240 to 180 during a Friday 0900 to 1500 timing plan.

Quantifying Benefits of Traffic Signal Retiming

This monograph is an exposition of several practice-ready methodologies for automatic vehicle identification (AVI) data collection systems. This includes considerations in the physical setup of the collection system as well as the interpretation of the data. An extended discussion is provided, with examples, demonstrating data techniques for converting the raw data into more concise metrics and views. Examples of statistical before-after tests are also provided. A series of case studies were presented that focus on various real-world applications, including the impact of winter weather on freeway operations, the economic benefit of traffic signal retiming, and the estimation of origin-destination matrices from travel time data. The technology used in this report is Bluetooth MAC address matching, but the concepts are extendible to other AVI data sources.