Liuhui Zhao

Cost–Benefit Analysis and Microclimate-Based Optimization of a RWIS Network

AbstractThe Road Weather Information System (RWIS) has been applied as an effective tool to collect weather and road surface temperature information and to assist operational decisions for snow and ice control activities. Current practices on siting regional RWIS stations rely on the knowledge and experiences of maintenance and operation personnel, which is subjective and inefficient. A two-stage sequential model is developed in this paper. The Stage-1 model optimizes the number and locations of RWIS stations, which intends to maximize spatial coverage with the least overlapping area, considering the variation of regional weather severity. The deployment of the optimized RWIS sites can be prioritized by the Stage-2 model, which maximizes the lifecycle profit subject to limited budget. The proposed methodology is applied to optimize a RWIS network for the State of New York.

Shockwave-Based Automated Vehicle Longitudinal Control Algorithm for Nonrecurrent Congestion Mitigation

A shockwave-based speed harmonization algorithm for the longitudinal movement of automated vehicles is presented in this paper. In the advent of Connected/Automated Vehicle (C/AV) environment, the proposed algorithm can be applied to capture instantaneous shockwaves constructed from vehicular speed profiles shared by individual equipped vehicles. With a continuous wavelet transform (CWT) method, the algorithm detects abnormal speed drops in real-time and optimizes speed to prevent the shockwave propagating to the upstream traffic. A traffic simulation model is calibrated to evaluate the applicability and efficiency of the proposed algorithm. Based on 100% C/AV market penetration, the simulation results show that the CWT-based algorithm accurately detects abnormal speed drops. With the improved accuracy of abnormal speed drop detection, the simulation results also demonstrate that the congestion can be mitigated by reducing travel time and delay up to approximately 9% and 18%, respectively. It is also found that the shockwave caused by nonrecurrent congestion is quickly dissipated even with low market penetration.

Analysis of Weather Impact on Travel Speed and Travel Time Reliability

Weather conditions may have significant impact on traffic flow. Under adverse weather, traffic speed reduces and congestion emerges. The joint effects of adverse weather and recurring traffic congestion throughout the day may lead to more unpredictable travel time. The objective of this study is to examine the impact of adverse weather on traffic speed and travel time reliability in various highways. Weather data collected from Road Weather Information System (RWIS) Environmental Sensor Stations (ESS) and speed data collected by INRIX are applied. Data for various highway classifications and different time periods are selected to conduct the comparative analysis. Travel time reliability is measured by the buffer index. It was found that adverse weather reduces traffic speed and leads to less travel time reliability. The extent of influence varies with precipitation intensity. The results may assist transportation agencies for traffic management and travelers for trip planning under adverse weather.