Development Of Guidelines For Triple Left And Dual Right Turn Lanes
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| Author | : Scott Allen Cooner |
| Publisher | : |
| Total Pages | : |
| Release | : 2011 |
| Genre | : Turning lanes |
| ISBN | : |
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, their research was needed to develop consistence 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, Tudor 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.
| Author | : |
| Publisher | : |
| Total Pages | : 354 |
| Release | : 2002 |
| Genre | : Left-turn lanes |
| ISBN | : |
| Author | : |
| Publisher | : |
| Total Pages | : 80 |
| Release | : 2004 |
| Genre | : Left-turn lanes |
| ISBN | : |
It is generally accepted that the level of service (LOS) at intersections significantly affects the overall LOS of the road system. It is also known that the LOS at an intersection can be adversely affected by frequently allowing left-turning vehicles to block through traffic. In addition, crash rates tend to be higher at intersections than on through sections of a road. The separation of left-turning vehicles from through traffic is therefore an important condition for the safe and effective operation of intersections. Existing guidelines for installing left-turn lanes have several limitations. They are mainly based on the traffic volumes at the intersection, and they use deterministic models with fixed gap acceptance and/or left-turn maneuver times. In addition, the guidelines for left-turn lanes for unsignalized intersections and signalized intersections must be specific for the type of intersection. In this study, new left-turn guidelines for both unsignalized and signalized intersections were developed on the basis of well-validated event-based simulation programs. Guidelines for unsignalized intersections were based on the percentage of left turns blocking through vehicles, whereas the guidelines for signalized intersections were developed using a minimum left-turn volume of either 85% left-turn capacity or LOS E delay (55 seconds/vehicle). In addition to the general guidelines, a prioritization tool that can be used to prioritize candidate intersections was developed. The prioritization tool accounts for both operational and safety aspects.
| Author | : Yi Qi |
| Publisher | : |
| Total Pages | : 126 |
| Release | : 2012 |
| Genre | : Right-turn lanes |
| ISBN | : |
Right-turn lanes provide space for the deceleration and storage of right-turn vehicles, and separate turning vehicles from through movements. Dual right-turn lanes are increasingly used at urban intersections primarily for two reasons: (1) to accommodate high right-turn demands and avoid turn-pocket overflows, and/or (2) to prevent right-turn vehicles that exit from a nearby upstream freeway off-ramp (on the left of the roadway) from abruptly changing too many lanes toward the right-turn lane at the intersection. In addition, a number of other factors may affect the decisions on the installation of dual right-turn lanes. However, warrants for dual right lane installation are almost non-existent, leaving traffic engineers to rely on engineering judgment. This research aims to develop warrants for installation of dual right-turn lanes at signalized intersections. Both the operational and safety benefits/costs were analyzed by surveying traffic engineers and by conducting traffic simulation-based analysis. Microscopic traffic simulation model, VISSIM, was used to quantify the operation benefits and Surrogate Safety Assessment Model (SSAM) developed by Siemens was used to analyze the safety gains due to installation of dual right-turn lanes.
| Author | : Zoltan Anthony Nemeth |
| Publisher | : |
| Total Pages | : 12 |
| Release | : 1976 |
| Genre | : Traffic flow |
| ISBN | : |
| Author | : |
| Publisher | : |
| Total Pages | : 50 |
| Release | : 2004 |
| Genre | : Left-turn lanes |
| ISBN | : |
In Missouri, multiple left-turns are gaining popularity. However, the installation of these multiple left-turn raises questions for which the Missouri Department of Transportation (MoDOT) has not yet developed answers. Specifically, MoDOT seeks guidance on: Criteria for determining when to install double and triple left-turns. The type of phasing to be used for dual and triple left-turn lanes. Whether to use "Dallas" or permitted lead-lag phasing for any left-turn lanes. Where to begin reducing the number receiving lanes downstream of an intersection with multiple left-turn lanes
| Author | : Kay Fitzpatrick |
| Publisher | : Transportation Research Board |
| Total Pages | : 62 |
| Release | : 2013 |
| Genre | : Left-turn lanes |
| ISBN | : 0309258987 |
"TRB's National Cooperative Highway Research Program (NCHRP) Report 745: Left-Turn Accommodations at Unsignalized Intersections presents guidance for the selection and design of left-turn accommodations at unsignalized intersections. The report includes 11 case studies of typical situations that illustrate the use of the guidance." -- publisher's description.
| Author | : L. K. Staplin |
| Publisher | : |
| Total Pages | : 256 |
| Release | : 1997 |
| Genre | : Older automobile drivers |
| ISBN | : |
| Author | : |
| Publisher | : |
| Total Pages | : 128 |
| Release | : 1995 |
| Genre | : Roads |
| ISBN | : |
Free right-turn (FRT) lanes are turning roadways at intersections that provide for free-flowing right-turn movements. The objective of the research presented in this report was to develop guidelines for FRT lanes at unsignalized intersections on rural two-lane highways in Nebraska. The development of the guidelines was based on a benefit-cost analysis, which determined the right-turn volumes required to justify the construction and maintenance of FRT lanes at these locations. The research involved the evaluation of the operational and safety effects of FRT lanes. The operational effects of FRT lanes were analyzed using kinematic and traffic flow models. Accident data analysis, field studies, and computer simulation of truck dynamics were used to evaluate the safety effects of FRT lanes. The results of these analyses were also used to determine acceptable design criteria for FRT lanes. A survey of other state agencies was conducted to identify any existing guidelines, design criteria, and experience that might be useful in developing the guidelines and evaluating the design criteria. Also, the concerns of citizens opposed to the removal of FRT lanes were examined in an effort to develop guidelines that might effectively address these concerns. The results of the research indicate that design-year right-turn AADTs ranging from 440 to 825 vehicles per day, depending on the percentage of trucks, are required to warrant a FRT lane at an unsignalized intersection of rural two-lane highways. A design speed of 40 mph was found to be a realistic design speed and the most cost-effective design speed for FRT lanes. However, design speeds up to 55 mph do not significantly reduce the cost effectiveness of a FRT lane. The AASHTO design criteria for curves on open highways were found to be appropriate for designing the curvature of FRT lanes. The AASHTO criteria for minimum-radii intersection curves were not acceptable. Also, acceleration lanes were found to improve the safety of the merging operations associated with FRT lanes. The results of the accident data analysis do not support the perceptions of concerned citizens regarding the safety benefits of FRT lanes. FRT lanes were not found to affect the frequency, severity, or types of accidents that occur at unsignalized intersections on rural two-lane highways. Thus, FRT lanes should not be perceived, or promoted, as traffic safety improvements. The benefits of FRT lanes are limited to improving the efficiency of right-turn movements.
| Author | : L. K. Staplin |
| Publisher | : |
| Total Pages | : 36 |
| Release | : 1997 |
| Genre | : Older automobile drivers |
| ISBN | : |
