Simulation-based Evaluation of Traffic Safety Performance Using Surrogate Safety Measures

2012 Traffic safety

Author : Hong Yang
Release : 2012
Genre : Traffic safety
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Book Synopsis Simulation-based Evaluation of Traffic Safety Performance Using Surrogate Safety Measures by : Hong Yang

Download or read book Simulation-based Evaluation of Traffic Safety Performance Using Surrogate Safety Measures written by Hong Yang. This book was released on 2012. Available in PDF, EPUB and Kindle. Book excerpt: Traffic safety evaluation is one of the most important processes in the analysis of transportation systems performance. The use of traditional crash-data-oriented methodologies to analyze traffic safety problems has been frequently questioned due to shortcomings such as unavailability and low quality of historical crash data. The advancement of traffic conflict techniques and micro-simulation tools motivated this dissertation to develop a simulation-based approach of combining micro-simulation models and traffic conflict technique to investigate the safety issues in traffic systems. The proposed simulation-based approach consists of two major components: the development of surrogate safety measures; and the integration of the developed surrogate safety measures with micro-simulation models. In this dissertation, a new surrogate safety measure is derived and applied in micro-simulation models to capture the conflict risk of the interactions among vehicles. The conceptual and computational logics of the proposed surrogate safety indicator are described in detail. A calibration procedure that focuses on safety evaluation using the simulation model with the new surrogate measure has been proposed. The proposed calibration approach has been developed based on the stochastic gradient approximation algorithms to find optimal parameters of the stochastic traffic simulation models. The calibration methodology has been implemented on a selected traffic simulation platform to test its performance. Simulated operational measurements and traffic conflict risk in terms of the surrogate safety measure are quantified and compared with observations derived from high resolution vehicle trajectory data. The calibrated traffic model has also been validated by using independent vehicle trajectory data saved as a hold-out sample. The results show that the fine-tuning of parameters using the proposed calibration approach can significantly improve the performance of the simulation model to describe actual traffic conflict risk as well as operational performance. The applicability of the proposed new surrogate measure and the simulation-based safety evaluation approach using this surrogate measure has been successfully demonstrated through several cases studies. The overall findings can inform road safety investigators as to how operations-oriented simulation models in conjunction with the surrogate safety measure can complement traffic safety evaluation in cases to which traditional approaches are not applicable.

Surrogate Safety Measures from Traffic Simulation Models

2003 Roads

Author : Douglas Gettman
Release : 2003
Genre : Roads
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Book Synopsis Surrogate Safety Measures from Traffic Simulation Models by : Douglas Gettman

Download or read book Surrogate Safety Measures from Traffic Simulation Models written by Douglas Gettman. This book was released on 2003. Available in PDF, EPUB and Kindle. Book excerpt: "This project investigates the potential for deriving surrogate measures of safety from existing microscopic traffic simulation models for intersections. The process of computing the measures in the simulation, extracting the required data, and summarizing the results is denoted as the Surrogate Safety Assessment Methodology. These surrogate measures could then be used to support traffic engineering alternatives evaluation with respect to safety for both signalized and unsignalized intersections. The report describes the five main activities of this project: (1) review of previous work in modeling of safety at traffic facilities (focusing on intersection safety modeling) using surrogate measures, (2) survey of the capabilities of existing traffic simulation models to support derivation of surrogate measures of safety, (3) identification of use cases and functional requirements for a surrogate safety assessment tool that interacts with traffic simulation model outputs, (4) specification of algorithms for calculating surrogate measures of safety appropriate for intersections, and (5) suggestions for validation activities to support the analysis potential for surrogate measures and compare surrogate measures from simulation models with field data and previous safety studies"--Technical report documentation page.

Surrogate Safety Assessment Model and Validation

2008 Traffic conflicts

Author :
Release : 2008
Genre : Traffic conflicts
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Book Synopsis Surrogate Safety Assessment Model and Validation by :

Download or read book Surrogate Safety Assessment Model and Validation written by . This book was released on 2008. Available in PDF, EPUB and Kindle. Book excerpt: Safety of traffic facilities is most often measured by counting the number (and severity) of crashes that occur. It is not possible to apply such a measurement technique to traffic facility designs that have not yet been built or deployed in the real world. This project has resulted in the development of a software tool for deriving surrogate safety measures for traffic facilities from data output by traffic simulation models. This software is referred to as SSAM, an acronym for the Surrogate Safety Assessment Model. The surrogate measures developed in this project are based on the identification, classification, and evaluation of traffic conflicts that occur in the simulation model. By comparing one simulated design case with another, this software allows an analyst to make statistical judgments about the relative safety of the two designs. The method is based on processing detailed trajectories of all vehicles in the simulation environment and identifying conflicts that occur between any two vehicles. An open-standard vehicle trajectory data format was designed, and support for this format has been added as an output option by four simulation model vendors/developers PTV (VISSIM), TSS (AIMSUN), Quadstone (Paramics), and Rioux Engineering (TEXAS). Eleven 'theoretical' validation tests were performed to compare the surrogate safety assessment results of pairs of simulated design alternatives. In some cases, these comparative tests showed clear agreement with traditional results from crash prediction models; and, in other cases, the results from SSAM utilizing the traffic simulation models were counterindicative. Typically, one design would exhibit a statistically significant lower number of conflicts, but the severity of conflicts that did occur would be higher. Nevertheless, SSAM does provide metrics for use by analysts in comparing traffic facility designs that do not have established crash statistics. More research work is necessary to refine the metrics for broader consumption by a general audience. A field validation exercise was completed to compare the output from SSAM with real-world crash records. Eighty-three intersections from British Columbia, Canada were modeled in VISSM and simulated under AM-peak traffic conditions. The processed conflict results were then compared with the crash records in a number of different statistical validation tests. In general, the correlation results between the outputs from the simulation models and the crash records were significant, with the regression model predicting crashes from conflict data exhibiting a correlation (R-squared) value of = 0.41. However, the simulation modeling effort did present a number of issues. Sensitivity analysis was performed to identify differences between the SSAM-related outputs of each simulation model vendors system on the same traffic facility designs. These comparative analyses provide some guidance to the relative use of surrogate measures data from each simulation system. For more information regarding the SSAM tool and user manual (FHWA-HRT-08-050) see companion report, PB2008-111196.

A Simulation-based Approach to Evaluate Safety Impacts of Increased Traffic Signal Density

2002 Roads

Author : Kenneth P. Drummond
Release : 2002
Genre : Roads
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Book Synopsis A Simulation-based Approach to Evaluate Safety Impacts of Increased Traffic Signal Density by : Kenneth P. Drummond

Download or read book A Simulation-based Approach to Evaluate Safety Impacts of Increased Traffic Signal Density written by Kenneth P. Drummond. This book was released on 2002. Available in PDF, EPUB and Kindle. Book excerpt: One of the most controversial access management techniques practitioners face is also one of the most common: restricting signal density. Increased signal density can improve access for minor approaches to a corridor; however, it can also increase delays and rear-end crashes for vehicles on the mainline (major) approach. An ability to evaluate the impacts of increased signal spacing is thus critical for decision makers. Because crash data are not always easy to obtain, a logical question arises: Can simulation models be used to evaluate the safety impacts of increased traffic signal density? This report describes a method for using simulation models to evaluate the safety impacts of increased traffic signal density in suburban corridors. Using 10 years of data from two major arterials in Virginia, actual crash rates were compared with operational performance measures simulated by the Synchro/SimTraffic model. As expected, crash rates were positively correlated with stops per vehicle and delay per vehicle and negatively correlated with mainline speed. Three findings were significant. First, the correlation between crash rates and select mainline performance measures (delay, speed, and stops) was relatively strong despite the inherent variability in crash rates: R2, a measure of explained variance in crash rates, yielded values from 0.54 to 0.89. Second, three distinct regimes relate stops per vehicle to signal density: the installation of the first few signals causes a drastic increase in stops, the addition of the next set of signals causes a moderate increase in stops, and the addition of a third set of signals does not significantly affect the number of stops per vehicle. Third, multiple regime models also relate delay per vehicle to signal density. This study recommends two practical applications. To the extent these mainline performance measures correlate with crashes, simulation modeling may be used to estimate safety impacts of increased signals, which is appealing because simulation packages are becoming easier to apply. Further, three regime models can suggest when, in the timeline of corridor development, the addition of a traffic signal is likely to degrade corridor performance significantly versus when it will have little effect, thereby allowing decision makers to expend political capital when it is most beneficial (e.g., the occasions when there is significant degradation of corridor performance). Most important, the approach herein suggests a long-range corridor-planning tool for evaluating the impacts of different access densities.

Proceedings of the Sixth International Conference of Transportation Research Group of India

2022-09-28 Technology & Engineering

Author : Lelitha Devi
Release : 2022-09-28
Genre : Technology & Engineering
Kind : eBook
Book Rating : 048/5 ( reviews)

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Book Synopsis Proceedings of the Sixth International Conference of Transportation Research Group of India by : Lelitha Devi

Download or read book Proceedings of the Sixth International Conference of Transportation Research Group of India written by Lelitha Devi. This book was released on 2022-09-28. Available in PDF, EPUB and Kindle. Book excerpt: This book comprises the proceedings of the Sixth International Conference of Transportation Research Group of India (CTRG2021) focusing on emerging opportunities and challenges in the field of transportation of people and freight. The contents of the volume include characterization of conventional and innovative pavement materials, operational effects of road geometry, user impact of multimodal transport projects, spatial analysis of travel patterns, socio-economic impacts of transport projects, analysis of transportation policy and planning for safety and security, technology enabled models of mobility services, etc. This book will be beneficial to researchers, educators, practitioners and policy makers alike.

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