The Experts below are selected from a list of 140799 Experts worldwide ranked by ideXlab platform
Mohamed Abdelaty - One of the best experts on this subject based on the ideXlab platform.
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an optimal variable speed limits system to ameliorate Traffic Safety risk
2014Co-Authors: Mohamed AbdelatyAbstract:Active Traffic Management (ATM) systems have been emerging in recent years in the US and Europe. They provide control strategies to improve Traffic flow and reduce congestion on freeways. This study investigates the feasibility of utilizing a Variable Speed Limits (VSL) system, one key part of ATM, to improve Traffic Safety on freeways. A proactive Traffic Safety improvement VSL control algorithm is proposed. First, an extension of the METANET (METANET: A macroscopic simulation program for motorway networks) Traffic flow model is employed to analyze VSL’s impact on Traffic flow. Then, a real-time crash risk evaluation model is estimated for the purpose of quantifying crash risk. Finally, optimal VSL control strategies are achieved by employing an optimization technique to minimize the total crash risk along the VSL implementation corridor. Constraints are setup to limit the increase of average travel time and the differences of the posted speed limits temporarily and spatially. This novel VSL control algorithm can proactively reduce crash risk and therefore improve Traffic Safety. The proposed VSL control algorithm is implemented and tested for a mountainous freeway bottleneck area through the micro-simulation software VISSIM. Safety impacts of the VSL system are quantified as crash risk improvements and speed homogeneity improvements. Moreover, three different driver compliance levels are modeled in VISSIM to monitor the sensitivity of VSL effects on driver compliance. Conclusions demonstrated that the proposed VSL system could improve Traffic Safety by decreasing crash risk and enhancing speed homogeneity under both the high and moderate compliance levels; while the VSL system fails to significantly enhance Traffic Safety under the low compliance scenario. Finally, future implementation suggestions of the VSL control strategies and related research topics are also discussed.
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an optimal variable speed limits system to ameliorate Traffic Safety risk
2014Co-Authors: Mohamed AbdelatyAbstract:Active Traffic Management (ATM) systems have been emerging in recent years in the US and Europe; they provide control strategies to improve Traffic flow and reduce congestion on freeways. This study investigates the feasibility of utilizing a Variable Speed Limits (VSL) system, one key part of ATM, to improve Traffic Safety on freeways. A proactive Traffic Safety improvement VSL control algorithm is proposed. First, an extension of the METANET Traffic flow model is employed to analyze VSL’s impact on Traffic flow. Then, a real-time crash risk evaluation model is estimated for the purpose of quantifying crash risk. Finally, optimal VSL control strategies are achieved by employing an optimization technique to minimize the total crash risk along the VSL implemented corridor. Constraints are set up to limit the increase of average travel time and the differences of the posted speed limits temporarily and spatially. This novel VSL control algorithm can proactively reduce crash risk and therefore improve Traffic Safety. The proposed VSL control algorithm is implemented and tested for a mountainous freeway bottleneck area through the micro-simulation software VISSIM. Safety impacts of VSL are quantified as crash risk improvements and speed homogeneity improvements. Moreover, three different driver compliance levels are modeled to monitor the sensitivity of driver compliance effects on VSL’s Safety benefits. Conclusions demonstrated that the proposed VSL system would improve Traffic Safety by decreasing crash risk and enhancing speed homogeneity. Future implementation suggestions of the VSL control strategies and related research are also discussed.
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artificial neural networks and logit models for Traffic Safety analysis of toll plazas
2002Co-Authors: Hassan T Abdelwahab, Mohamed AbdelatyAbstract:Little research has been conducted to evaluate the Traffic Safety of toll plazas and the impact of electronic toll collection (ETC) systems on highway Safety, but analyses indicate that toll plazas do contribute to Traffic accidents. Traffic Safety issues related to toll plazas and ETC systems were studied using the 1999 and 2000 toll plaza Traffic accident reports of the Central Florida expressway system. The analysis focused on accident location with respect to the plaza structure (before, at, after plaza) and driver injury severity (no injury, possible, evident, severe injuries). Two well-known artificial neural network (ANN) paradigms were investigated: the Multi-Layer Perceptron and Radial Basis Functions neural networks. The performance of ANN was compared with calibrated logit models. Modeling results showed that vehicles equipped with ETC devices, especially medium/heavy-duty trucks, have higher risk of being involved in accidents at the toll plaza structure. Also, main-line toll plazas have a higher percentage of accident occurrence upstream of the toll plaza. In terms of driver injury severity, ETC users have a higher chance of being injured when involved in an accident. Older drivers tend to have higher risk of experiencing more severe injuries than younger drivers. Female drivers have a higher chance of experiencing a severe injury than do male drivers.
Ximiao Jiang - One of the best experts on this subject based on the ideXlab platform.
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Development of zone system for macro-level Traffic Safety analysis
2014Co-Authors: Mohamed Abdel-aty, Ximiao JiangAbstract:Various geographic units have been used in macro-level modeling. Amongst these units, Traffic analysis zones (TAZs) have been broadly employed in many macroscopic Safety studies. Nevertheless, no studies questioned the validity of TAZs for crash analysis at the macro-level crash modeling. In this study, we point out several possible problems of TAZs as spatial units for macroscopic Safety studies. Current TAZs with homogenous crash rates were combined into new single zones. Then we created ten new zonal systems by different zone aggregation levels. The optimal zonal scale for Traffic Safety analysis zones (TSAZ) was determined using the Brown-Forsythe test. It was found that the zone system with about 1:2 aggregation was the optimal zone system for macroscopic Safety modeling. Thus we develop what we call Traffic Safety analysis zones (TSAZs) that has the potential of reducing several possible problems of TAZs. Also it was shown that TSAZ based models had better fit compared to TAZ based models.
Mohamed Abdel-aty - One of the best experts on this subject based on the ideXlab platform.
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Development of zone system for macro-level Traffic Safety analysis
2014Co-Authors: Mohamed Abdel-aty, Ximiao JiangAbstract:Various geographic units have been used in macro-level modeling. Amongst these units, Traffic analysis zones (TAZs) have been broadly employed in many macroscopic Safety studies. Nevertheless, no studies questioned the validity of TAZs for crash analysis at the macro-level crash modeling. In this study, we point out several possible problems of TAZs as spatial units for macroscopic Safety studies. Current TAZs with homogenous crash rates were combined into new single zones. Then we created ten new zonal systems by different zone aggregation levels. The optimal zonal scale for Traffic Safety analysis zones (TSAZ) was determined using the Brown-Forsythe test. It was found that the zone system with about 1:2 aggregation was the optimal zone system for macroscopic Safety modeling. Thus we develop what we call Traffic Safety analysis zones (TSAZs) that has the potential of reducing several possible problems of TAZs. Also it was shown that TSAZ based models had better fit compared to TAZ based models.
B Bienkiewicz - One of the best experts on this subject based on the ideXlab platform.
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mobile mapping technology of wind velocity data along highway for Traffic Safety evaluation
2010Co-Authors: Susan Chen, Fangbin Chen, Juhua Liu, B BienkiewiczAbstract:Traffic Safety of highway vehicles under strong crosswind gust and other hazardous driving conditions has become a pressing issue for modern highway transportation and economy. It is known that the actual wind environment at the typical height of a moving vehicle varies considerably from one segment to another even on the same highway, because of influence of the specific terrain and surroundings. Therefore, accurate crosswind velocity data in both time and spatial domains are needed, for a rational assessment of Traffic Safety risks for various moving vehicles on highways in windy conditions. In addition to site-specific wind data which can be used for most vehicles, vehicle-specific crosswind velocity is often required for an accurate Safety assessment of high-sided vehicles with unique shapes. A mobile mapping technology aiming at collecting site-specific as well as vehicle-specific wind velocity data for Traffic Safety evaluations was developed. Such technology integrates a 3D sonic anemometer and geospatial video mapping system, mounted on a vehicle driven along highways at a normal (cruising) speed. As a result, both vehicle-specific and general site-specific crosswind velocity can be directly "sensed" and collected by using a high-sided vehicle or a streamlined car as the test vehicle. A field test of the developed technology with a high-sided truck driven on mountainous sections of the interstate I-70 (in Colorado) was conducted. The crosswind data at six selected feature locations along I-70, representing different roadside environments, was analyzed. Wind-tunnel investigations employing the scaled models of the truck used in the field test as well as a common streamlined sedan car were conducted to evaluate the accuracy and the feasibility of the developed technology.
Khaled A Abbas - One of the best experts on this subject based on the ideXlab platform.
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Traffic Safety assessment and development of predictive models for accidents on rural roads in egypt
2004Co-Authors: Khaled A AbbasAbstract:This paper starts by presenting a conceptualization of indicators, criteria and accidents' causes that can be used to describe Traffic Safety. The paper provides an assessment of Traffic Safety conditions for rural roads in Egypt. This is done through a three-step procedure. First, deaths per million vehicle kilometers are obtained and compared for Egypt, three other Arab countries and six of the G-7 countries. Egypt stands as having a significantly high rate of deaths per 100 million vehicle kilometers. This is followed by compiling available Traffic and accident data for five main rural roads in Egypt over a 10-year period (1990-1999). These are used to compute and compare 13 Traffic Safety indicators for these roads. The third step for assessing Traffic Safety for rural roads in Egypt is concerned with presenting a detailed analysis of accident causes. The paper moves on to develop a number of statistical models that can be used in the prediction of the expected number of accidents, injuries, fatalities and casualties on the rural roads in Egypt. Time series data of Traffic and accidents, over a 10 years period for the considered roads, is utilized in the calibration of these predictive models. Several functional forms are explored and tested in the calibration process. Before proceeding to the development of these models three ANOVA statistical tests are conducted to establish whether there are any significant differences in the data used for models' calibration as a result of differences among the considered five roads.
