This paper presents an evaluation of the use of lighted pavement markers parallel to an intersection stop bar for three treatment intersections in Houston, Texas. The line of pavement markers was active, with a red light displayed from each marker during the red interval of the traffic signal. Each lighted pavement marker contained multiple LEDs, which operated such that each marker displayed an alternating wigwag pattern. The intended impact of the pavement markers was to reduce red light running violations and crashes on the intersection approach to an arterial that had an at-grade light rail line within its median. A before-and-after study was conducted to determine changes in crashes, red light running violations, and right turn on red violations at the study sites (right turns on red are prohibited at all the study sites). The analysis results showed that the lighted pavement markers reduced red light running violations at all three treatment sites, with two of the three reductions being statistically significant. Right turn on red violations were also reduced, and the reduction was statistically significant at all three treatment sites. A fourth site was chosen as a comparison (nontreatment) site, and the before-and-after study showed no notable change in the number of red light running violations or right turn on red violations at this site.

No abstract

U-turn lanes are commonly provided at at-grade diamond interchanges with frontage roads to reduce delays for U-turning traffic and for the interchange as a whole; however, there are currently many unknowns related to their design, operation, and use. Researchers of this study assessed the existing practice of U-turn implementation by evaluating operations of U-turn lanes at 25 diamond interchanges in Texas through field data collection and simulation analysis. Researchers determined the performance and limitations of U-turn lanes under various geometric and operational conditions, identified and investigated several factors affecting U-turn lane use, and determined the anticipated effectiveness of proposed solutions to U-turn operational issues. This paper provides implementable guidelines for designing and operating U-turn lanes at diamond interchanges. Among the ten countermeasures studied in this paper, closing nearby driveways, adding acceleration lane for U-turn departures, and separating U-turn departures from conflicting traffic using pylons were found to be effective solutions to improve U-turn operations.

The intersection and mandatory movement lane control signs placed on intersection approaches are critical to safe and efficient intersection operations. Ramp, frontage road, and cross-street approaches to interchanges often widen at intersections to accommodate additional through or turn lanes. Currently, there is inconsistency in conveying to drivers how they should align themselves upstream of a diamond intersection to maneuver for their desired turning movement as the intersection widens. These inconsistencies can result in drivers making an incorrect lane selection that may result in late lane changes or illegal turns. This paper focuses on the expectancy violations that were discovered by a driver survey portion of a larger project that included practitioner surveys and a field evaluation of sign alternatives. A computer-based driver survey sampled 204 Texas drivers in four cities. The questions reported in this paper focused on driver expectations of lane movement and assignment on frontage road approaches to cross streets on freeway on- and off-ramps. Findings that showed that drivers are often incorrect in their assumptions about lane assignment when approaching intersections indicate a greater need for advanced lane control signs. A new sign design, adopted from Australian practice, that graphically shows lane additions and drops was the most effective for cases in which the downstream geometry varied from the driver's expectations.

A recent research project investigated the operational benefits of modern roundabouts for high-speed locations that serve heavy vehicles, while developing examples of best practices for design. The research team compiled proven results from designs in other states and collected and analyzed data from within and outside of Texas to develop updated design guidance, which can be used to implement roundabout designs that accommodate oversize/overweight (OSOW) vehicles in rural areas. This paper summarizes activities and findings from that project. Project activities indicate that the drone-based data collection effort, along with a computer algorithm-based method for data reduction, was an effective and efficient alternative to traditional data collection and reduction methods for this project. Findings from field data and simulation confirmed practices in other states that roundabouts can be designed to accommodate not only heavy vehicles but also OSOW vehicles in rural locations with high-speed approaches. The roundabout with the largest diameter studied (180 ft) had the best performance, but the smallest roundabout (120-ft diameter) was also able to accommodate larger vehicles at lower volumes, and roundabouts of all sizes generally outperformed two-way stop-controlled intersections in simulation results.