Recognizing the need for responsible highway agencies to effectively manage emerging autonomous vehicles (AV) flows in contending with daily recurrent congestion, this study presents a systematic procedure for understanding the impacts of AV flows on traffic conditions under different AV behavioral mechanisms (i.e., car-following and lane-changing), and different penetration rates. Research results show that the presence of AV flows, depending on their adopted behavioral mechanisms, may have significant (either positive or negative) impacts on the overall traffic conditions. Hence, it is essential for responsible highway agencies to have proper operational guidelines to manage and coordinate AV flows. To demonstrate the proposed methodology, this study has carried out extensive simulation experiments using a congested segment of the MD-100 network (a multilane highway segment located in Maryland) under various AV penetration rates and observable behavioral patterns. The collected Measures of Effectiveness highlight that at each AV penetration level there exists a set of optimal behavioral patterns for the AV flows to coordinate with non-AV flows via the Vehicle to Infrastructure or Vehicle to Vehicle infrastructure so as to maximize the roadway capacity and minimize the resulting highway congestion.

Despite the fact that both traffic researchers and highway agencies have devoted considerable efforts over the past few decades to improving intersection safety, development of effective strategies to contend with this vital issue remains a challenging task. This research presents the field evaluation results of a Dilemma Zone Protection System (DZPS) implemented at two hazardous intersections in Maryland, U.S.A. The deployed DZPS can offer both proactive and reactive protections to drivers approaching a signalized intersection during a yellow phase. Field evaluations conducted at two intersections with DZPS deployed confirmed a 100% detection rate for red-light-running vehicles, timely activation of the all-red extension to prevent right-angle crashes, and effectively discouraging drivers from taking aggressive “pass” decisions during the yellow or all-red phases. The potential extension of the DZPS for speed harmonization on arterial traffic flows is also discussed.

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A real-time advanced traveler information system for traffic heading to Ocean City, Maryland, is presented. It can provide dynamic route choice guidance for en route travelers, offer web-based historical data for pretrip tourists, and perform real-time traffic monitoring as well as emergency evacuation for responsible agencies with its 40 detectors. The proposed system is designed to contend with most critical issues associated with real-time operations, including automated detection of incidents, reliable estimation of missing data, and continuous updates of historical databases. Implementation results demonstrate that the travel time information displayed by the proposed system has been well received by drivers and is viewed as the primary resource for choice of routes to Ocean City. The evolution of traffic volumes on alternative routes during congested periods reveals that the travel time information from variable message signs not only provides guidance to drivers but also leads to better use of roadway capacity and results in more throughputs for the same period of operation.

Contending with recurrent congestion on commuting corridors has long been a challenging and pressing issue for responsible highway agencies. However, effective strategies to mitigate the congestion level and the accompanying safety issues on those highway segments remain to be developed. In response to such needs, this study presents an innovative system that integrates variable speed control and travel time information for alleviating day-to-day recurrent congestion on a highway corridor. The system presented in this study includes a set of algorithms for setting variable speeds for different highway segments based on traffic conditions detected from roadway sensors and a well-calibrated license-plate-recognition system for displaying the estimated travel time. Field experiments of the proposed system on MD-100 for 8 weeks showed that with proper speed control in real time, the congested highway segment can achieve a higher throughput, a stable traffic condition, and a shorter travel time.