This paper demonstrates the capabilities and benefits of using dynamic traffic assignment (DTA) to analyze traffic impacts caused by transit services. The City of Austin’s proposed urban rail system is used as a case study. The urban rail connects the CBD, the University of Texas at Austin campus, and other large traffic generators. The majority of the rail system shares right-of-way with traffic. However, several segments have completely dedicated guideway. Previous analyses have focused either on microsimulation (which is limited in spatial area and does not consider route choice changes) or regional planning (which typically lacks detailed inputs and does not directly model transit impedances in the traffic assignment process). DTA provides a connection between these two methods: it can model route choice behavior using realistic inputs at a fine time scale across a large spatial area. Five scenarios with varying mode split percentages were modeled. At low ridership levels, corridors with major geometric modifications experienced more congestion. This caused travel pattern changes, increasing the volume on nearby parallel corridors.
Construction activities and numbers of related work zones on urban freeways have grown significantly. The most problematic work zones occur on roads that are already fully loaded with traffic. The impact of work zones on mobility and safety makes success of the traffic control plan vital. Full freeway closures are sometimes implemented to expedite project completion and thereby reduce the cumulative impact of construction on travelers. Traffic diversion strategy is one way to improve the management of traffic and reduce user costs. An effective diversion plan makes drivers become aware of likely work zone delays and available alternate routes increasing the chances that they will choose alternate routes. Construction on the SH-71/IH-35 interchange required complete closure of all IH-35 main lanes. IH-35 is an important business corridor, conveniently connecting four large Texas cities, as well as, facilitating trade between Mexico and the United States. A parallel route, the SH-130 toll road, was made free to travelers during those closures. The purpose of this paper is to investigate driver route switching behavior during IH-35 closure and explore options for relieving delays on IH-35 during future closures. The Austin highway network was analyzed. However, usage of SH-130 was less than anticipated, and there was significant traffic queuing on IH-35 at the work zone. Analysis was based on integrating data from all available sources. In order to compare conditions of a non-closure weekend to the closure weekend, five recent months were considered.