Hyungjun Park

Development and Evaluation of Enhanced IntelliDrive-Enabled Lane Changing Advisory Algorithm to Address Freeway Merge Conflict

Freeway merge conflicts contribute significantly to freeway congestion. With the capabilities that will be available in an IntelliDrive environment, which enables vehicle-to-vehicle and vehicle-to-infrastructure communications, new approaches to managing freeway merges are possible. In this paper, an enhanced IntelliDrive enabled lane changing advisory algorithm was developed with a variable gap size concept. This algorithm first calculates anticipated lead–lag gap sizes with the equations of motion prepared for a car and a truck and for three vehicle dynamics (accelerating, maintaining current speed, and decelerating). The algorithm then provides lane changing advisories to freeway main-line vehicles (selected on the basis of the calculated variable gap sizes) to create more space within the ramp merging area. Evaluation conducted with a VISSIM microscopic traffic simulation model of a freeway network in Virginia showed that the proposed algorithm has the potential to address freeway merge conflicts. The maximum operational improvement observed was 6.4% higher average speed in the freeway main line within a merge area. Up to a 5.2% reduction in emissions was achieved. Further analysis conducted in terms of the sensitivity of algorithm performance to driver compliance rates suggested that a very high compliance rate (90% or higher) was necessary for the proposed algorithm to work as intended.

Integrated Traffic–Communication Simulation Evaluation Environment for IntelliDrive Applications Using SAE J2735 Message Sets

Vehicle-to-vehicle and vehicle-to-infrastructure communications made possible by IntelliDrive will enable new transportation applications and services. To understand and quantify potential benefits from Intelli-Drive applications, these applications should be evaluated before field deployment. An IntelliDrive simulation environment was developed; it replicated precise vehicular movements, incorporated IntelliDrive wireless communications based on wireless access in vehicular environments–dedicated short-range communication standards, and simulated real IntelliDrive message sets defined in the Society of Automotive Engineers J2735 standard. A case study of a prototype lane changing advisory algorithm revealed that communication delays were not likely to be a significant factor and showed maximum delays of only 55 ms for the basic safety message (BSM) and 1.3 ms for the a la carte message (ACM). The probability of successful communication can affect evaluation results. For example, for a lane changing advisory algorithm, the probability of successful transmission of a series of required messages—three BSMs and one ACM—was only 50% when fewer than 120 vehicles were within a communication radius of 50 m. This result implied a significant degradation in algorithm performance. The results demonstrate the feasibility of integrating traffic and communication simulation models and the need to consider both components in IntelliDrive evaluation.

Investigating Benefits of IntelliDrive in Freeway Operations: Lane Changing Advisory Case Study

Merging conflicts created by freeway on-ramps contribute significantly to freeway congestion. Although the need to address merging conflicts is evident, transportation engineers have limited options with existing traffic surveillance and management tools. Fortunately, IntelliDriveSM, the integration of vehicles and the infrastructure through wireless communication, offers the potential for much more active management of the surface transportation system, providing capabilities that may be of significant benefit in ramp management. Given this background, in this research, a lane changing advisory algorithm was developed to explore the potential of IntelliDriveSM in improving freeway ramp management. Utilizing new IntelliDriveSM capabilities (highly detailed individual vehicular data and personalized advisory information provision), the proposed algorithm attempts to reduce merging conflicts by encouraging early mainline freeway lane changes to create more space in ramp merging areas. An evaluation of the algorithm was conducted using a PARAMICS microscopic simulation model of a heavily traveled freeway network in Orange County, California, for morning peak hours. The results have revealed that IntelliDriveSM has significant potential in improving freeway operations. More specifically, the lane changing advisory algorithm improved the network performance by enabling 4.3% more vehicle miles traveled while reducing vehicle hours traveled by 4.6%, which resulted in 9.3% higher average speeds.

Identifying Deficient Pavement Sections by Means of an Improved Acceleration-Based Metric

Transportation agencies devote significant resources toward the collection of highly detailed and accurate pavement roughness data by using profiler vans to support pavement maintenance decisions. However, these agencies often cannot afford to measure roughness annually for the whole pavement network. This study introduced an improved acceleration-based metric, an index normalized by vehicle operating speed, to be used on a regular basis to screen pavement segments that are likely to be deficient; then a profile van can be sent to accurately measure the roughness condition. A profile van collected pavement profile data on 50 mi (80 km) of roadway; these data were then used to calculate the international roughness index (IRI). Meanwhile, two tablet computers were placed on the vehicle floor to collect data, including three-way accelerations, GPS coordinates, and vehicle speeds. A normalized acceleration-based index was created by incorporating a speed factor. Furthermore, logistic regression models were created to evaluate the effectiveness of the proposed index in identifying deficient pavement sections [IRI ≥ 140 in./mi (2.21 m/km)]. The proposed acceleration-based metric was able to identify between 80% and 93% of all deficient pavement sections. This research points to the feasibility of using a cost-effective acceleration-based application for network screening, a process that will reduce the total mileage of pavement sections needing to be measured and meanwhile still identify locations for which maintenance work is necessary.

Investigating Cybersecurity Issues in Active Traffic Management Systems

Active traffic management (ATM) systems have been introduced by transportation agencies to manage recurrent and non-recurrent congestion. ATM systems rely on the interconnectivity of components made possible by wired and/or wireless networks. Unfortunately, this connectivity that supports ATM systems also provides potential system access points that results in vulnerability to cyberattacks. This is becoming more pronounced as ATM systems begin to integrate Internet of Things (IoT) devices. Hence, there is a need to rigorously evaluate ATM systems for cyberattack vulnerabilities, and explore design concepts that provide stability and graceful degradation in the face of cyberattacks. In this research, a prototype ATM system along with a real-time cyberattack monitoring system were developed for a 1.5-mile section of I-66 in Northern Virginia. The monitoring system detects deviation from expected operation of an ATM system by comparing lane control states generated by the ATM system with lane control states deemed most likely by the monitoring system. This comparison provides the functionality to continuously monitor the system for abnormalities that would result from a cyberattack. In the case of any deviation between two sets of states, the monitoring system displays the lane control states generated by the back-up data source. In a simulation experiment, the prototype ATM system and cyberattack monitoring system were subject to emulated cyberattacks. The evaluation results showed that the ATM system, when operating properly in the absence of attacks, improved average vehicle speed in the system to 60 mph (a 13% increase compared to the baseline case without ATM). However, when subject to cyberattack, the mean speed reduced by 15% compared to the case with the ATM system and was similar to the baseline case. This illustrates that the effectiveness of the ATM system was negated by cyberattacks. The monitoring system allowed the ATM system to revert to an expected state with a mean speed of 59 mph and reduced the negative impact of cyberattacks. These results illustrate the need to revisit ATM system design concepts as a means to protect against cyberattacks in addition to traditional system intrusion prevention approaches.

Exploration of Operational Concepts of Interoperability for Robust Interregional Transportation System Operations

Regional transportation operations centers (TOCs) are at the core of managing and operating a complex surface transportation system. To ensure reliable transportation services, particularly during emergency situations when transportation is vital, uninterrupted operations of TOCs should be guaranteed. Achieving TOC interoperability is of great importance. Interoperability of TOCs can be understood as the ability of one TOC to access and manage some set of the resources of another (remote) TOC. TOC interoperability can allow each metropolitan area or in some cases each state to achieve more robust and seamless interregional operations. In addition, interoperability may provide each region with a better understanding of each partners practices and thus promote more consistent and coordinated transportation systems operations. Although these benefits are compelling, TOC interoperability cannot be easily established because of the complex technical and institutional situations of existing centers. Given this background, this study explored various operational concepts and developed a methodology to achieve interregional TOC interoperability. The methodology consists of four steps: (a) develop an emergency backup plan for each TOC, (b) establish relationships among TOCs, (c) develop a communications network, and (d) establish institutional interoperability between designated TOCs. In a case study, the proposed methodology was applied to the five regional TOCs in the Commonwealth of Virginia.

Investigating Driver Response Time to Freeway Merge Advisories in a Connected Vehicle Environment

Vehicular conflict is one of the major causes of congestion in freeway merge areas. With the emerging connected vehicle environment, more proactive strategies can be developed and implemented to improve merging operations with enhanced safety and mobility. The freeway merge assistance system, made possible with connected vehicles, ensures smoother merging through the early identification and dynamic notification of merging opportunities by advisory message. However, given that the effectiveness of this mobility application depends entirely on drivers’ responses to the advisory messages, a proper understanding of driver response to the new generation of dynamic advisory messages is a necessity. A detailed analysis of driver response time to advisory messages from the freeway merge assistance system was conducted on the basis of the data collected in a field test with 68 naive participants. The analysis results showed that the perception–reaction time increased as the available gap size decreased. An estimated 0.64-s difference was observed between cases with large and small gaps and implies varied perception–reaction times for various traffic conditions. Second, the perception–reaction time decreased as the advisory became more direct and proactive, with an observed 1.30-s decrease in perception–reaction time between the most direct and indirect advisories. It is therefore recommended that advisory messages should be direct and clear. The actual lane-changing time did not change much, regardless of advisory type or available gap size. The implications of these results are of significance in the design and implementation of connected vehicle–enabled mobility applications.

Scenario-Driven Computer-Based Regional Incident Management Training

Incident management is one of the most important functions of a transportation management center (TMC). To efficiently and effectively manage complex regional incidents that affect transportation facilities under the jurisdiction of multiple agencies, TMC operators must be trained appropriately. Recently, a team of universities including the University of Maryland, University of Virginia, and Rensselaer Polytechnic Institute developed a computer-based training tool for regional incident management to be used by the I-95 Corridor Coalition. In its role on the team, the University of Virginia conducted research to support the development of detailed regional incident scenarios to provide content for the computer-based simulation tool. The method created to develop the incident scenarios is presented, with clear examples. Major findings from the research effort include the benefits of rapid prototyping and the usefulness of extensible markup language (XML) for structured content development.

New Methodology for Development of Regional Vehicle-Mapping Tables for MOBILE Emissions Model

Among the many input factors to the MOBILE emissions model, vehicle miles traveled (VMT) fractions (the percentage of VMT for different types of vehicles by roadway functional classes) plays an important role because different types of vehicles produce emissions at different rates. In addition, since the vehicle classification scheme of MOBILE is different from the FHWA vehicle types used in traffic data collection, a vehicle-mapping table that converts VMT fractions from FHWA types to MOBILE types deserves special attention. The research described in this paper produced a new methodology to develop a vehicle-mapping table by using readily available data sources, namely, (a) vehicle registration data from the Department of Motor Vehicles of Virginia and (b) Vehicle Inventory and Use Survey data from the Bureau of the Census. To evaluate the new methodology, a vehicle-mapping table for Virginia was developed and then compared with three commonly used mapping-table methodologies. In addition, on the basis o...