Safety Evaluation of Median U-Turn Crossover-Based Intersections

Al-Omari, Ma’en Mohammad Ali; Abdel-Aty, Mohamed; Lee, Jae Young; Yue, Lishengsa; Abdelrahman, Ahmed

doi:10.1177/0361198120921158

Cited by 11 publications

(10 citation statements)

References 11 publications

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“…The safety performance of UAIDs can be assessed using different measures, such as theoretical number of conflict points, real-life crash data, and traffic microsimulation analysis using surrogate safety measures. Several studies have investigated the safety performance of different UAIDs designs using crash data and simulation models including the SSM design ( 20–25 ), the DLT ( 6, 26–28 ), the continuous green T-intersection (CGT) ( 29, 30 ), and the jughandle intersection ( 31 ). Najaf and Pulugurtha ( 32 ) compared the safety performance of six UAIDs (unsignalized MUT, signalized MUT, the SSM, bowtie, forward jughandle, and reverse jughandle) relative to three conventional intersection designs.…”

Section: Previous Workmentioning

confidence: 99%

Operational and Safety Performance Evaluation of Parallel Flow Intersection

Abobakr

Esawey

Osama

2022

Transportation Research Record

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Unconventional arterial intersection designs have recently gained popularity as an alternative solution to alleviate congestion and mitigate safety problems of at-grade signalized intersections. This study investigates the operational and safety performance of the parallel flow intersection (PFI) under different balanced and unbalanced traffic volume conditions in comparison with a conventional counterpart using VISSIM microsimulation and Surrogate Safety Assessment Model software. The operational performance of the two intersections was based on the overall intersection capacity and the average vehicle delay. The safety performance, on the other hand, was based on the number and severity of simulated conflicts. The results showed that the PFI had a higher capacity compared with the conventional intersection under balanced volume conditions. Under unbalanced volume levels, the PFI outperformed the conventional intersection especially with an increase of left-turn volumes. Moreover, the PFI enhanced the safety conditions relative to the conventional intersection by eliminating all the crossing conflicts under all balanced and unbalanced volume levels and reducing the total number and severity of conflicts at all volume conditions. The study provides guidelines for the optimal spacing distance between the main and secondary intersections for the implementation of the PFI based on its safety and operational impacts on the intersection.

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Section: Previous Workmentioning

confidence: 99%

Operational and Safety Performance Evaluation of Parallel Flow Intersection

Abobakr

Esawey

Osama

2022

Transportation Research Record

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“…A method for the dynamic use of the left-turn lane for opposite through traffic to improve the efficiency of a signalized intersection has also been proposed [20]. Some scholars have studied the effect of U-turn facilities [21], while other scholars have specialized in optimizing the phase of left-turn signals at intersections to improve left-turning traffic problems [22].…”

Section: Introductionmentioning

confidence: 99%

Evaluation and Analysis Model of the Length of Added Displaced Left-Turn Lane Based on Entropy Evaluation Method

Pan

Ying

Luo

et al. 2021

Journal of Advanced Transportation

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As the number of vehicles continues to grow in China, the problem of urban traffic congestion gets more serious, particularly at intersections. As a new type of unconventional intersection, the displaced left-turn (DLT) intersection has been widely recognized to improve the efficiency of intersections with heavy left-turn traffic flows. Converting an existing intersection into an intersection with additional DLT lanes is a valuable solution. However, the studies on DLT intersections mainly focus on performance, applicability, and safety. The guidelines on the specific engineering design process mostly come from experience, and the study on the considering multifactor design method is still insufficient. Therefore, this paper proposed an evaluation and analysis model of the lengths of added DLT lanes based on the entropy evaluation method, in which VISSIM and Surrogate Safety Assessment Model (SSAM) software were adopted for simulation. A design process for the length of the added DLT lanes was proposed with this model. An urban intersection in Xi’an was taken as a case study, and the application of the model and the design process was studied in detail. After selecting four evaluation indicators, the model was applied to calculate and analyze the optimal length of the added DLT lanes under 45 different traffic volume combinations. The recommended lengths of different situations were within the range recommended in the guidebook published by Federal Highway Administration. The results of the case study proved that the model proposed in this paper was advanced, reasonable, and practical.

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“…While the Al-Omari et al study has quantified the safety benefits associated with signalized MUTs using the empirical Bayes (EB) method, several important areas of investigation remain unexplored ( 16 ). Research specific to unsignalized reduced left-turn conflict intersections continues to be limited to the works conducted before the HSM ( 4–6 ) or that include RCUT intersections ( 22–26 ).…”

mentioning

confidence: 99%

“…It should be noted that the cross-sectional study design employed by Al-Omari et al to estimate CMFs for signalized MUTs represented an appropriate approach, given that preconversion period data are limited for signalized MUTs in Michigan that have been in place for several decades ( 16 ). However, a before-and-after approach is preferred where sufficient pre- and postconversion data are available, as the difference in safety performance observed via cross-sectional studies could be the result of either known or unknown factors—including the countermeasure being evaluated ( 27 ).…”

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confidence: 99%

Safety Performance of Unsignalized Median U-Turn Intersections

Kay

Gates

Savolainen

et al. 2022

Transportation Research Record

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Alternative intersection designs can offer safety and operational benefits with potentially lower costs than conventional intersections when implemented in the proper setting. The Federal Highway Administration has previously identified a subset of alternative designs called reduced left-turn conflict intersections as a proven safety countermeasure. Median U-turn intersections (also known as “Michigan lefts” or “boulevard turnarounds”) are one such design that accommodates all left-turn movements via directional U-turn crossovers within the median. Prior work has consistently shown that median U-turn intersections can provide superior safety performance when used in the appropriate conditions. However, research that is specific to unsignalized reduced left-turn conflict intersections continues to be limited to work conducted before the Highway Safety Manual, or which includes restricted crossing U-turn intersections. This study included the evaluation of historical traffic crashes and volume data at 95 unsignalized intersections in the state of Michigan. This included the collection of data for 39 median U-turn sites and 56 reference group sites to estimate safety performance functions and crash modification factors that can be used when considering future conversions. Ultimately, crash modification factors for fatal and injury crashes of 0.438 and 0.686 are recommended when converting intersections with undivided two-lane two-way major approaches and four-lane divided boulevard major approaches, respectively. Although there was no significant difference in property damage only crashes associated with converting intersections with undivided, two-lane, two-way major approaches, a crash modification factor of 1.325 is recommended for property damage only crashes specific to conversions with four-lane, divided boulevard major approaches.

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Safety Evaluation of Median U-Turn Crossover-Based Intersections

Cited by 11 publications

References 11 publications

Operational and Safety Performance Evaluation of Parallel Flow Intersection

Operational and Safety Performance Evaluation of Parallel Flow Intersection

Evaluation and Analysis Model of the Length of Added Displaced Left-Turn Lane Based on Entropy Evaluation Method

Safety Performance of Unsignalized Median U-Turn Intersections

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