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0-7136, This project compiled and reviewed existing road cross-section guidance (for urban, suburban, and rural environments) from across the United States, along with research findings, to identify content that would be appropriate for inclusion in Texas-based guidelines for road cross-section optimization. A separate project task focused on considering the data needs for assessing a proposed cross-section treatment, using the results from previous efforts to determine if existing guidance and data are sufficient to develop cross-section optimization guidelines. Based on the information obtained in those tasks, this report provides recommended guidelines for selecting optimal cross-sections for highways in Texas. Those guidelines include suggested revisions to the TxDOT Roadway Design Manual and Access Management Manual.

The project team compiled and reviewed existing road cross-section guidance (for urban, suburban, and rural environments), along with research findings, to identify content that would be appropriate for inclusion in Texas-based guidelines for cross-section optimization. A subsequent task focused on considering the data needs for assessing a proposed cross-section treatment, using the results from previous efforts to determine if existing guidance and data are sufficient to develop cross-section optimization guidelines. The project concluded by providing recommendations for further evaluation and adoption.

Project 0-6568, MUTCD 2009 Edition suggests the use of Flashing Yellow Arrow (FYA) indication in replacement of green ball indication for permissive left-turn signal in presence of separate signal heads. Currently, there is no clear guidance on how to implement flashing yellow operations with PPLT in Texas. The objective of this research project is to developed guidelines for FYA with PPLT operations. To fulfill this goal, the researchers (1) reviewed and synthesized national and peer state practices on FYA PPLT; (2) surveyed traffic engineers and drivers ; (3) deployed FYA PPLT operation at five selected intersections in Texas cities; (4) identified software and hardware issues associated with the deployment of FYA PPLT; and (5) evaluated the safety performance of FYA PPLT based on the historical crash data analysis and field traffic conflict studies. According to the findings of this research, it is recommended that FYA signal indication can be used at most of signals with PPLT operations to improve intersection safety and to comply with the requirements of the MUTCD. However, FYA PPLT operation is not recommended at busy intersections that have high left-turn volumes and opposing volumes, and it should be implemented with great cautions at intersections where lead-lead left-turn phasing is used.

MoDOT project# TR201515, US DOT contract #DTRT13-G-UTC37, Carlos Sun : http://orcid.org/0000-0002-8857-9648, The J-turn, also known as RCUT (Restricted Crossing U-Turn) and Superstreet, is an innovative geometric design that can improve intersection safety. Even though this design has been in use in several states for many years, there is very little research-based guidance for several design parameters. A driving simulator study was conducted to analyze the parameters of lane configuration, U-turn spacing, and signage. Two lane configurations were examined: 1) acceleration/deceleration configuration where acceleration and deceleration lanes are provided and 2) deceleration only configuration where only deceleration lanes are provided. Lane configuration was found to be the most important parameter affecting J-turn safety based on speed-differentials. The only significant interaction effect among parameters was between lane configuration and U-turn spacing. The acceleration/deceleration configuration performed better than the deceleration only configuration with 66.3% fewer safety critical events. Vehicle trajectories and average lane change locations showed that U-turn spacing impacted significantly the acceleration/deceleration configuration (e.g. average merge locations changed by 96% to 101%) but not the deceleration only configuration. No strong preference was demonstrated by the study subjects for either the directional or the diagrammatic signage style. This report presented the first human factors study of the J-turn focused on developing design guidance. This human factors approach complements other traditional approaches such as crash analysis and micro-simulation.

Project 0-6112, Left- or right-turn lanes at intersections improve safety and operations by separating turning and through vehicles. At intersections, with heavy turning demand, it may be necessary to provide multiple turn lanes. Triple left-turn (TLT) and dual right-turn (DRT), lanes are still considered as relatively new designs that many agencies are reluctant to use, so they are somewhat limited in Texas., Guidelines for TLT or DRT lanes are almost nonexistent, leaving traffic engineers to rely on judgment for their designs. Therefore, this research was needed to develop consistent guidance. The 0-6112 project achieved two primary project goals: (1) development, of geometric and signal design guidelines for TLT and DRT lanes; and (2) evaluation of the safety and operational performance of, TLT and DRT sites in Texas., Researchers conducted field studies at 5 TLT and 20 DRT, primarily in the Dallas-Fort Worth and Houston urban areas, in order to, evaluate lane utilization patterns, saturation flow rates, conflicts, and other operational factors. The research team also analyzed, safety performance by investigating the crash history of the 25 sites using three techniques: collision diagrams, field conflict study, and comparison study. The results revealed that TLT lanes do not experience any major safety issues and also concluded that, in, general, a well-designed DRT lane does not cause significantly higher crash frequency or severity compared to single right-turn, lanes., Based on the results of this research and the geometric and signal design guidelines, TxDOT and other agencies should be, confident that well-designed TLT and DRT lanes can be implemented to address heavy turning demand at key intersections. The, evaluation of these multiple turn lane sites in Texas revealed that they perform well from both operational and safety standpoints., TLT and DRT lanes are not appropriate for all situations, and their use should be supported by an operational analysis. Other, techniques (grade separation, signal timing, etc.) might be better solutions for a particular site, especially when considering the, effects of adjacent intersections, pedestrian/bicycle movements, and other key factors. Researchers developed a product, Keys to, Successful Public Outreach, which is useful for implementing multiple turn lane projects.

134573, The formation of queues on a highway facility is a sign of the presence of operationally, inefficient sections of the facility. Queuing occurs at intersections in large part due to overflow, or inadequacy of turn bays, inadequate capacity, or poor signal progression. The ODOT Location, and Design (L&D) Manual Volume 1 has storage requirements for both signalized and, unsignalized intersections. Figures 401-9E and 401-10E of the L&D Manual provide the, required turn lane storage lengths which should be compared with the real world conditions to, check for adequacy of these lengths as a measure of ensuring that accesses to the turn lanes are, not blocked. In addition to the projected turn lane volume, ODOT’s methodology incorporates, both deceleration (based on the speed of the roadway) and potential blockage from the adjacent, through lane. Currently, however, there are no records whether these storage lengths computed, by the methodology put forth in this manual are valid and accurately represent the actual, conditions at intersections in Ohio. Consequently, collecting real world traffic and queue storage, data at some intersections and analyzing these data is valuable for validating and/or updating the, model ODOT is currently using. Accordingly, the purpose of this research was to collect traffic, and queue storage data at some intersections in Ohio and use the collected data to validate and/or, update the model in ODOT’s L&D Manual.

134573, Queuing occurs at intersections mostly due to overflow or inadequacy of turn bays. The ODOT L&D, Manual Volume 1 has storage requirements for both signalized and unsignalized intersections. Figures, 401-9E and 401-10E of the L&D Manual provide the required turn lane storage lengths which should be, compared with the real world conditions to check for adequacy of these lengths as a measure of ensuring, that accesses to the left turn lanes are not blocked. In addition to the projected turn lane volume, ODOT’s, methodology incorporates both deceleration (based on the speed of the roadway) and potential blockage, from the adjacent through lane. Currently, however, there are no records whether these storage lengths, computed by the methodology put forth in this manual are valid and accurately represent the actual, conditions at intersections in Ohio. This study used real world traffic and queue storage data at some, intersections and analyzed these data to validate the model ODOT is currently using. This study used the, observed field data to evaluate the ODOT’s model of storage length at intersections. In addition, the, queue storage lengths observed from field data were compared with the prediction results of HCS and, SYNCHRO computer packages. The model evaluation task evaluated the level of precision of each of the, three models (ODOT, HCS, and SYNCHRO) with respect to the field data observation. L&D Manual, lead the way by accurately predicting the observed queues by about 81.6% and closely followed by HCS, which also had a 79.2% prediction accuracy. SYNCHRO was by far the lowest with a 46.0% prediction, accuracy.