Evaluating Safety Impacts of Access Management Alternatives with the Surrogate Safety Assessment Model

2018 ◽  
Vol 2672 (17) ◽  
pp. 120-128 ◽  
Author(s):  
Kyung Min Kim ◽  
Mitsuru Saito ◽  
Grant G. Schultz ◽  
Dennis L. Eggett
Keyword(s):  
Multiple Access ◽  
Safety Assessment ◽  
Impact Analysis ◽  
Simulation Software ◽  
Assessment Model ◽  
Access Management ◽  
Left Turn ◽  
Crash Data ◽  
Simulated Environment ◽  
Management Alternatives

In a traditional safety impact analysis, it is necessary to have crash data on existing roadway conditions and a few years must pass before accumulating additional crash data to evaluate the safety impact of an improvement. This is a time-consuming approach and there remains uncertainty in the crash data integrity. The surrogate safety assessment model (SSAM) was developed for resolving these issues. With SSAM, a conflict analysis is performed in a simulated environment. A planned improvement alternative is modeled and no physical installation of the alternative is needed. This study evaluated if SSAM can be used to assess the safety of a highway segment in terms of the number and type of conflicts and to compare the safety effects of multiple access management alternatives. An evaluation of the effect of converting a two-way left-turn lane (TWLTL) into a raised median on a section of an urban street was performed using SSAM working on VISSIM simulation’s trajectory files. The analysis showed that a raised median would be much safer than a TWLTL median for the same level of traffic volume, with approximately 32 to 50 percent reduction in the number of crossing conflicts. The analysis showed that about 34,000 to 38,000 veh/day would be the demand level where the median conversion is recommended for the four-lane study section. The study concluded that the combination of a simulation software program with SSAM could be a viable surrogate analysis approach for evaluating and comparing the safety effects of multiple access management alternatives.

scholarly journals Statistical Analysis of Safety Performance of Displaced Left-Turn Intersections: Case Studies in San Marcos, Texas

2020 ◽  
Vol 17 (18) ◽  
pp. 6446
Author(s):  
Wenrui Qu ◽  
Qiao Sun ◽  
Qun Zhao ◽  
Tao Tao ◽  
Yi Qi
Keyword(s):  
Statistical Analysis ◽  
Traffic Signal ◽  
Safety Performance ◽  
Access Management ◽  
Left Turn ◽  
Crash Data ◽  
Safety Issues ◽  
The Road ◽  
San Marcos ◽  
Driver Acceptance

Displaced left-turn (DLT) intersections are designed to increase the mobility of vehicles by relocating the left-turn lane (lanes) to the far-left side of the road upstream of the main signalized intersection. Since DLT is a relatively new design and very limited crash data are available, previous studies have focused mainly on the analysis of its operational performance rather than its safety performance. To fill this gap, in this study, we investigated the safety performance of two DLT intersections located in San Marcos, Texas. Crash data from 2011 to April 2018 were extracted from the TxDOT Crash Record Information System (CRIS). These crash data were analyzed using two different approaches, i.e., statistical analysis and collision diagram-based analysis. The results of this study indicated that DLT did not increase the overall crash frequencies at the studied intersections. Traffic crashes related to left turns and right turns were reduced significantly by DLT. Meanwhile, it also caused safety issues related to traffic signage, traffic signal, geometric design, and access management at DLT intersections. Thus, in the implementation of DLT intersections, traffic engineers need to carefully consider different aspects of the DLT intersection design, including access management, traffic signal coordination, and driver acceptance. As a result of these analyses, recommendations were provided for the safe implementation of the DLT design in the future.

scholarly journals Safety Evaluation of Turbo-Roundabouts with and without Internal Traffic Separations Considering Autonomous Vehicles Operation

2021 ◽  
Vol 13 (16) ◽  
pp. 8810
Author(s):  
Tullio Giuffrè ◽  
Anna Granà ◽  
Salvatore Trubia
Keyword(s):  
Autonomous Vehicles ◽  
Safety Assessment ◽  
Safety Evaluation ◽  
Simulation Models ◽  
Safety Performance ◽  
Assessment Model ◽  
Crash Data ◽  
Vehicle Trajectories ◽  
Traffic Conflicts ◽  
Surrogate Measures

The paper presents a microsimulation approach for assessing the safety performance of turbo-roundabouts where Cooperative Autonomous Vehicles “CAVs” have been introduced into the traffic mix alongside conventional vehicles “CVs”. Based on the analysis of vehicle trajectories from VISSIM and subsequent analysis of traffic conflicts through the Surrogate Safety Assessment Model (SSAM), the research aims to evaluate the safety benefits of turbo-roundabouts where the lanes are physically separated by raised curbs, compared to roundabouts without such curbs. The paper will then describe the methodological path followed to build VISSIM models of turbo-roundabouts with and without raised curbs in order to calibrate the simulation models and estimate the potential conflicts when a higher percentage of CAVs are introduced into the traffic mix. A criterion has been also proposed for setting properly the principal SSAM filters. The results confirmed both higher safety levels for turbo-roundabouts equipped with raised lane dividers compared to turbo-roundabout solutions without curbs, and better safety conditions under the traffic mix of CVs and CAVs. Therefore, it follows that, in absence of crash data including CAVs, the surrogate measures of safety are the only approach in which the safety performance of any roundabout or road entity can be evaluated.

scholarly journals Evaluation and Analysis of CFI Schemes with Different Length of Displaced Left-Turn Lanes with Entropy Method

2021 ◽  
Vol 13 (12) ◽  
pp. 6917
Author(s):  
Binghong Pan ◽  
Shasha Luo ◽  
Jinfeng Ying ◽  
Yang Shao ◽  
Shangru Liu ◽  
...  
Keyword(s):  
Fuel Consumption ◽  
Heavy Traffic ◽  
Efficiency Index ◽  
Entropy Method ◽  
Sustainable Transportation ◽  
Assessment Model ◽  
Left Turn ◽  
Traffic Demand ◽  
Traffic Efficiency ◽  
Multi Attribute Decision Making

As an unconventional design to alleviate the conflict between left-turn and through vehicles, Continuous Flow Intersection (CFI) has obvious advantages in improving the sustainability of roadway. So far, the design manuals and guidelines for CFI are not enough sufficient, especially for the displaced left-turn lane length of CFI. And the results of existing research studies are not operational, making it difficult to put CFI into application. To address this issue, this paper presents a methodological procedure for determination and evaluation of displaced left-turn lane length based on the entropy method considering multiple performance measures for sustainable transportation, including traffic efficiency index, environment effect index and fuel consumption. VISSIM and the surrogate safety assessment model (SSAM) were used to simulate the operational and safety performance of CFI. The multi-attribute decision-making method (MADM) based on an entropy method was adopted to determine the suitability of the CFI schemes under different traffic demand patterns. Finally, the procedure was applied to a typical congested intersection of the arterial road with heavy traffic volume and high left-turn ratio in Xi’an, China, the results showed the methodological procedure is reasonable and practical. According to the results, for the studied intersection, when the Volume-to-Capacity ratio (V/C) in the westbound and eastbound lanes is less than 0.5, the length of the displaced left-turn lanes can be selected in the range of 80 to 170 m. Otherwise, other solutions should be considered to improve the traffic efficiency. The simulation results of the case showed CFI can significantly improve the traffic efficiency. In the best case, compared with the conventional intersection, the number of vehicles increases by 13%, delay, travel time, number of stops, CO emission, and fuel consumption decrease by 41%, 29%, 25%, 17%, and 17%, respectively.

Safety Assessment Method for Equipment of Urban Rail Transit Network Operation

2014 ◽  
Vol 513-517 ◽  
pp. 3958-3963 ◽  
Author(s):  
Bo Gao ◽  
Ling Xi Zhu ◽  
Xue Mei Xiao
Keyword(s):  
Safety Assessment ◽  
Spatial Information ◽  
Urban Rail Transit ◽  
Assessment Model ◽  
Rail Transit ◽  
Source Information ◽  
Transit Network ◽  
Urban Rail ◽  
Network Operation ◽  
Urban Rail Transit Network

Based on the multi-source information fusion and complex network theory, through studying the effective matching and integration of safety equipment and spatial information of urban rail transit network operation, a safety assessment model is proposed: through equipment fusion and the node fusion, the global safety parameter is obtained, which is accurate in description and evaluation of urban rail transit operating than the partial safety factors and realize the transform from microscopic description to macroscopic description.

Safety Assessment of Railway Dangerous Goods Transportation Based on Set Pair Analysis

2013 ◽  
Vol 869-870 ◽  
pp. 288-292
Author(s):  
Dong Jie Liu ◽  
Zhen Lin Wei
Keyword(s):  
Safety Assessment ◽  
Assessment Model ◽  
Engineering System ◽  
Set Pair Analysis ◽  
System Research ◽  
Analytic Hierarchy ◽  
Dangerous Goods ◽  
Index Weight ◽  
Hierarchy Process ◽  
Pair Analysis

In order to overcome the drawbacks that occur when traditional safety assessment methods do not consider the certain and uncertain characteristics of information and in order to enhance the calculation efficiency, a new Identical Discrepancy Contrary (IDC) system is safety comprehensive assessment model based on Set Pair Analysis is established. Incorporating the Analytic Hierarchy Process (AHP) to obtain the index weight, this model analyses the uncertainties in the degree of connection acquired by assessment, and then makes the identical discrepancy contrary system research on the certainty and uncertainty of information in the engineering system.

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