Traffic Theory

Many medium and small-size metropolitan areas in the U.S. face increasing traffic problems similar to large metropolitan areas. These metropolitan areas have responded primarily by expanding their road network and capacity. This paper explores the possibility of using a HOT lane in a medium-size metropolitan area for the same purpose. A detailed analysis and a suggested HOT lane solution are prepared for Greensboro-Winston-Salem-High Point metropolitan area. While high congestion are not widespread in the region now, a highway corridor is identified based on forecasted high...

Adaptive traffic signal control as well as transit signal priority (TSP) have both been viewed as important opportunities for reducing overall traffic congestion and improving bus transit service. However few studies have been conducted on combining them. A dynamic signal timing optimization model was developed in this research, which aims at reallocating green times among the phases with considering the realtime traffic flow condition and the bus priority request. In the model, both arrival and departure flows are described by time- dependent functions, the arrival of a bus with priority...

Several factors contribute to traffic congestion on highway facilities including adverse weather conditions. However, the extent of weather impacts on traffic flow and congestion delay on freeways is not fully known. This study analyzed an extensive set of historical traffic data from the state of California to gain a better understanding of the proportion of traffic delay that can be directly attributed to weather. A congestion estimation model was developed to estimate vehicle delays directly attributed to rain on 17 urban freeway corridors. It was found that delay due to rain ranged...

In this project, a novel approach has been developed to estimate the traffic states on arterial road links controlled by signalized intersections using both loop detector data and signal phasing information. The authors derived a trapezoidal fundamental diagram that includes two occupancy thresholds to categorize the traffic states into three different regimes: uncongested, congested, and downstream queue spillback. The parameters used to compute these two thresholds are closely related to road geometry, detector layout, signal settings, and vehicle dynamics, which can be obtained from the...