Steven Venglar

Dynamic Traffic Assignment Evaluation of Hurricane Evacuation Strategies for the Houston-Galveston, Texas, Region

The Houston–Galveston, Texas, region has experienced several major hurricanes in recent years. During the evacuation for Hurricane Rita in 2005, the Texas Department of Transportation (DOT) decided to implement contraflow operations on I-45 to relieve massive evacuee congestion departing Houston to the north. The decision to implement contraflow was a difficult one because it involved multiple jurisdictions and required extensive coordination of manpower and resources from various entities. After the Hurricane Rita experience, the Texas DOT implemented a new strategy, referred to as “evaculane,” in which evacuation traffic could use the outside paved shoulder as a traveling lane when an evacuation was under way and evaculane signing beacons were activated. The objective is to increase capacity along key evacuation routes while avoiding the need for full-scale contraflow operation whenever possible. The evaculane on I-10 was successfully put into use during the Hurricane Ike evacuation in 2008. With the widening and completion of evaculanes on I-10 and US-290 as well as a partial contraflow plan for the I-45 corridor, the Texas DOT sponsored a study to develop a decision support tool to help determine whether these strategies would adequately handle the evacuation demand for various Houston–Galveston region evacuation scenarios. This paper describes the quantitative assessment of the performance of alternative evacuation strategies using a dynamic traffic assignment model, DynusT. The evaluation results indicated the evaculanes on I-10 and US-290 can sufficiently handle high evacuation demand on both routes without contraflow operation. In addition, a partial contraflow plan for I-45 was shown to provide sufficient capacity to handle high evacuation demand in lieu of full-scale contraflow operation.

Super 2 highways in Texas: operational and safety characteristics

As traffic volumes increase in both urban and rural areas, so do demands on the highway network. Specifically, as rural traffic volumes rise in Texas, the pressure on the states network of two-lane highways rises accordingly. Previous research in Texas demonstrated that periodic passing lanes can improve operations on two-lane highways with average daily traffic lower than 5,000 vehicles. These highways, called Super 2 highways, can provide many of the benefits of a four-lane alignment at a lower cost. A recent project expanded on that research to develop design guidelines for passing lanes on two-lane highways with higher volumes. Researchers investigated the effects of volume, terrain, and heavy vehicles on traffic flow and safety. This paper discusses findings from field observations and crash analysis of existing Super 2 highway corridors in Texas and computer modeling of traffic conditions on a simulated Super 2 corridor. Results indicate that passing lanes provide added benefit at higher traffic volumes by reducing crashes, delay, and percent time spent following. Empirical Bayes analysis of crash data reveals a 35% reduction in expected nonintersection crashes with injuries. Simulation results indicate that most passing activity takes place within the first mile of the passing lane, so additional passing lanes can offer greater benefit than longer passing lanes. Whether new passing lanes are added or existing lanes are lengthened, the incremental benefit diminishes as additional length is provided and the highway more closely resembles a four-lane alignment.

Operational Characteristics of Super 2 Highways in Texas

As traffic volumes increase in many jurisdictions in both urban and rural areas, the demand on the highway network also increases. Specifically, as rural traffic volumes rise in Texas, the pressure on the states network of two-lane highways rises accordingly. High proportions of heavy vehicles compound the problem and contribute to a decrease in safety as impatient drivers attempt to pass slower vehicles in no-passing zones or to pass trucks, despite diminished sight distance beyond such vehicles. Previous research in Texas demonstrated that periodic passing lanes can improve operations on two-lane highways with low to moderate volumes; these Super 2 highways can provide many benefits of a four-lane alignment at lower cost. The current Texas Roadway Design Manual contains these guidelines for highways with average daily traffic (ADT) lower than 5,000 vehicles per day. A current project expands on that research to develop design guidelines for passing lanes on two-lane highways with higher volumes. The project investigates the effects of volume, terrain, and heavy vehicles on traffic flow. This paper discusses findings from field observations of existing Super 2 highway corridors in Texas and computer modeling of traffic conditions on a simulated Super 2 corridor. Results indicate that passing lanes do provide added benefit at higher traffic volumes by reducing delay and percent time spent following. The incremental benefit of adding passing lanes or adding length to lanes diminished, and the effects of ADT on operations were more substantial than the effects of terrain or truck percentage for the study corridor.

Real-time optimization at diamond interchanges

Due to the complexity of road traffic movements occurring within urban interchanges and increasing levels of demand, many diamond interchanges on roads are experiencing serious congestion. The closely spaced traffic signals with high volume turning traffic create a complex control scenario. The diamond interchange offers the unique opportunity to integrate many innovative technologies into a system that is small enough to be manageable, yet complex enough to present a challenging control environment. Developing a real time, multi modal, traffic adaptive interchange control system is a research objective of the Intelligent Vehicle Highway System (IVHS) Research Center of Excellence Program of the Texas Transportation Institute. This research effort will integrate a variety of technologies into a single control system that will increase traffic performance and demonstrate IVHS concepts in advanced traffic management systems. Through the use of video imaging equipment, traffic information processing, and real time optimization and control, road users will experience less delay, less congestion and fewer safety problems at diamond interchanges.

Warrants for Active Warning Devices at Low-Volume Highway-Rail Grade Crossings

In order to utilize funds from the Highway-Rail Grade Crossing Safety Program, Section 130 of Title 23 United States Code (U.S.C.), states must prioritize public highway-rail crossings for improvements. With nearly 10,000 open public crossings in Texas to prioritize for Section 130 funds, an automated ranking procedure capable of generating a useful priority list can be instrumental for efficient fund allocation. Findings from this research were used develop the following products: warrants to identify crossings that may benefit from upgrades; revised Texas Priority Index (TPIrev); the Texas Passive Crossings Index (TPCI); and an integrated prioritization methodology.