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Author: Yousteena Bocktor Publisher: ISBN: Category : Languages : en Pages :
Book Description
"Motor-vehicle turning maneuvers at intersections are often involved in crashes and serious injuries, in particular collisions involving vulnerable road users. In Canada alone, 30% of fatalities and 40% of serious injuries took place in intersections. Thus, to improve intersection safety, geometric design related treatments have been implemented and studied in past literature. These include curb radius reduction and curb extensions which aim to reduce turning speeds and crossing distances. The radius effects and treatments have been investigated for large intersections and road curves in rural areas using observed crash and point-speed measures, with limited studies examining small urban intersections. With the help of modern data collection techniques (video footage and GPS data), this study aims to fill the gaps presented in the literature on the investigation of the safety of curb radii and other geometric elements in local urban intersections using surrogate safety measures derived from vehicle trajectories and statistical regression models. More specifically, this research aims at: (1) develop a methodology to evaluate the impact of the curb radius on the speed of vehicle turning maneuvers in local intersections with small radius using Montreal video trajectory data and a cross-sectional approach. (2) To evaluate the safety effectiveness of curb radius reduction as a traffic calming treatment using a naïve before-after study and video data collected from two intersections in Toronto, Canada. In addition to speeds, post-encroachment time is used as a surrogate indicator, (3) To expand on the use of GPS smartphone data for establishing a methodology for evaluating the safety of turning movements to overcome the shortcomings of video cameras. For this purpose, GPS-based surrogate safety measures (85th percentile, median speeds, and deceleration) were extracted and modeled using mixed-effect regression models for a large data set from Quebec City.Among other results, a statistically positive and significant association between the radius and speed measures was observed for the video trajectory data. For instance, in the cross-sectional analysis, an increase of 1-meter in the curb radius results in an increase of 0.775 kph for the 85th speed and 1.208 kph for the median speed for all turns. For the before-after study, an average decrease was witnessed for all speed measurements for both intersections studied after the curb reduction treatment implementation. The countermeasure contributed to 1.6 kph and 0.783 kph decrease for 85th percentile and median speed, respectively, for both intersections when examined using the mixed-effects linear regression models. Lastly, using GPS smartphone data, the findings also support the relation between exhibited speeds and the measured corner curb radius. Using regression models of speeds, for every 1-meter increase in the measured curb radius, a statistically significant increase of 0.4 kph in both 85th percentile and median speeds was observed. Other intersections attributes, like the signalization, had an influence on the speed measures. As for the deceleration models, an increase of 1-meter in the radius resulted in a 0.01 m/s2 increase in the severity, thus, decreasing the safety of the intersection. Overall, the effectiveness of curb radius and reduction treatment was confirmed in the three different case studies. Despite the modest impacts in most of the cases, the importance of radius reductions is implied. Also, future work is required to address the limitations presented by the filtering techniques for the GPS data. Moreover, cross-calibration of the models can be used to evaluate the means of data collection by collecting GPS data for the video trajectory models and vise-versa"--
Author: Yousteena Bocktor Publisher: ISBN: Category : Languages : en Pages :
Book Description
"Motor-vehicle turning maneuvers at intersections are often involved in crashes and serious injuries, in particular collisions involving vulnerable road users. In Canada alone, 30% of fatalities and 40% of serious injuries took place in intersections. Thus, to improve intersection safety, geometric design related treatments have been implemented and studied in past literature. These include curb radius reduction and curb extensions which aim to reduce turning speeds and crossing distances. The radius effects and treatments have been investigated for large intersections and road curves in rural areas using observed crash and point-speed measures, with limited studies examining small urban intersections. With the help of modern data collection techniques (video footage and GPS data), this study aims to fill the gaps presented in the literature on the investigation of the safety of curb radii and other geometric elements in local urban intersections using surrogate safety measures derived from vehicle trajectories and statistical regression models. More specifically, this research aims at: (1) develop a methodology to evaluate the impact of the curb radius on the speed of vehicle turning maneuvers in local intersections with small radius using Montreal video trajectory data and a cross-sectional approach. (2) To evaluate the safety effectiveness of curb radius reduction as a traffic calming treatment using a naïve before-after study and video data collected from two intersections in Toronto, Canada. In addition to speeds, post-encroachment time is used as a surrogate indicator, (3) To expand on the use of GPS smartphone data for establishing a methodology for evaluating the safety of turning movements to overcome the shortcomings of video cameras. For this purpose, GPS-based surrogate safety measures (85th percentile, median speeds, and deceleration) were extracted and modeled using mixed-effect regression models for a large data set from Quebec City.Among other results, a statistically positive and significant association between the radius and speed measures was observed for the video trajectory data. For instance, in the cross-sectional analysis, an increase of 1-meter in the curb radius results in an increase of 0.775 kph for the 85th speed and 1.208 kph for the median speed for all turns. For the before-after study, an average decrease was witnessed for all speed measurements for both intersections studied after the curb reduction treatment implementation. The countermeasure contributed to 1.6 kph and 0.783 kph decrease for 85th percentile and median speed, respectively, for both intersections when examined using the mixed-effects linear regression models. Lastly, using GPS smartphone data, the findings also support the relation between exhibited speeds and the measured corner curb radius. Using regression models of speeds, for every 1-meter increase in the measured curb radius, a statistically significant increase of 0.4 kph in both 85th percentile and median speeds was observed. Other intersections attributes, like the signalization, had an influence on the speed measures. As for the deceleration models, an increase of 1-meter in the radius resulted in a 0.01 m/s2 increase in the severity, thus, decreasing the safety of the intersection. Overall, the effectiveness of curb radius and reduction treatment was confirmed in the three different case studies. Despite the modest impacts in most of the cases, the importance of radius reductions is implied. Also, future work is required to address the limitations presented by the filtering techniques for the GPS data. Moreover, cross-calibration of the models can be used to evaluate the means of data collection by collecting GPS data for the video trajectory models and vise-versa"--
Author: Saroch Boonsiripant Publisher: ISBN: Category : Global Positioning System Languages : en Pages :
Book Description
The identification of roadway sections with a higher than expected number of crashes is usually based on long term crash frequency data. In situations where historical crash data are limited or not available, surrogate safety measures, based on characteristics such as road geometries, traffic volume, and speed variation are often considered. Most of existing crash prediction models relate safety to speed variation at a specific point on the roadway. However, such point-specific explanatory variables do not capture the effect of speed consistency along the roadway. This study developed several measures based on the speed profiles along road segments to estimate the crash frequency on urban streets. To collect speed profile data, second-by-second speed data were obtained from more than 460 GPS-equipped vehicles participating in the Commute Atlanta Study over the 2004 calendar year. A series of speed data filters have been developed to identify likely free-flow speed data. The quantified relationships between surrogate measures and crash frequency are developed using regression tree and generalized linear modeling (GLM) approaches. The results indicate that safety characteristics of roadways are likely a function of the roadway classification. Two crash prediction models with different set of explanatory variables were developed for higher and lower classification roadways. The findings support the potential use of the profile-based measures to evaluate the safety of road network as the deployment of GPS-equipped vehicles become more prevalent.
Author: European Conference of Ministers of Transport Publisher: OECD Publishing ISBN: 9282103781 Category : Languages : en Pages : 286
Book Description
Speeding is the number one road safety problem in a large number of OECD/ECMT countries. It is responsible for around one third of the current, unacceptably high levels of road fatalities. Speeding has an impact not only on accidents but also on the ...
Author: Kristin Kersavage Publisher: ISBN: Category : Languages : en Pages :
Book Description
Reducing the number and severity of crashes on highways and streets is of high importance for government officials and transportation professionals in the United States. Substantial research has focused on various speed metrics, such as operating speeds and the posted speed limit, and their relationship to safety, such as crash frequency and crash severity. Crash severity is the safety measure most often linked to measures of speed and is based on dissipation of kinetic energy. However, many aspects of the relationships between speed metrics and crash frequency and risk have yet to be studied in depth, so a complete understanding of speeding-related crashes is unknown. Design speeds are used to establish geometric design criteria, and operating speed results from the geometric design process. Posted speed limits may be established based on operating speeds or by statute. When posted speed limits are inconsistent with design or operating speeds, road safety performance may be affected. A more complete understanding of the relationship between safety performance and operating speeds, posted speed limits, and design speeds may produce rational speed limits and lead to improved safety performance on roadways.This research combined real-time vehicle probe speed data, roadway inventory data, and crash data to assess crash risk and crash frequency.This thesis first determined the risk of a crash on two-lane rural highways based on operating speed metrics, differences between speed metrics, and traffic volume data. Results from the crash risk analysis indicate that operating speeds in 1-minute and 5-minute averages improve the statistical fit and prediction of binary logistic regression models. Higher traffic volumes and operating speeds higher than either the road average speed or road reference speed were associated with increased crash risk. Whereas, variations in travel speeds between vehicles were associated with decreased crash risk. This thesis also analyzed the frequency of crashes on horizontal curve segments of two-lane rural roadways using operating speed data, differences among speed metrics, traffic volume data, roadway inventory data, and crash data. Negative binomial regression models improve the statistical fit and prediction of crash frequency models compared to random-effects negative binomial regression. Generally, increases in the differences between operating speed and road average speed and the differences between operating speed and inferred design were associated with an increase in crash frequency. Increases in the differences between inferred design speed and posted speed limit were also associated with an expected increase in crash frequency; however, increases in the operating speed variance and in the difference between operating speeds and posted speed limit were associated with an expected decrease in crash frequency.
Author: Akshaey Sabhanayagam Publisher: ISBN: Category : Languages : en Pages :
Book Description
According to the US Department of Transportation, around 20 people die on a daily basis in a signalized intersection, with most of these resulting from angle or head-on collisions. The US-DOT's Federal Highway Administration (FHWA) has identified modern roundabout intersections to be substantially safer than signalized intersections, due in part to the reduction in conflict points from 32 in a traditional signalized intersection to 8 in a modern roundabout. Despite the increased adoption of modern roundabouts across the US, there are a number of specific design elements for which the direct impact they have on operational and safety related performance of the roundabout remains unknown. To be specific, there is currently no conclusive research on the direct effects related to the introduction of a reverse curve (S-curve) on the approach to a roundabout. Moreover, what are the impacts of S-curves of varying geometries on the approach to a roundabout? This research employed a series of microsimulation-based analyses to investigate the speed related impacts related to the introduction to S-curves on the entry to a roundabout. An existing roundabout, in Amherst, MA, USA was used as a case study for this experiment. The data at each approach of the roundabout was collected by a static camera strategically placed to attain both the pedestrian and vehicle count during peak traffic hours. The data was manually reviewed to determine the upstream and downstream vehicle counts. The dimensions and angles of the existing roundabout were measured from Google earth and the image was extracted to AutoCaD Civil 3D. Since the objective is to check whether S-curves near an approach have a significant impact in speed, the deflection angle of the roundabout was not altered. The turning radius and angle at the approach was cross verified by measuring it on site. The existing roundabout was considered as the base model. The four approaches of the roundabout have different entry angles and radii. The revised models were drafted by strategically placing the S-curve at each approach and by steadily increasing their deflection angle and approach radius. The base and revised models cases were initially modelled, after which the conventional linear approach was modified to an S-curve and evaluated. Field data from the locations were to and calibrate microsimulation models on AIMSUN. The resulting trajectory data was analyzed for both the base case as well as three levels of experimental S-curves (ranging from 30 to 60 degrees) on each roundabout approach (16 total). The results provide evidence to suggest that a significant reduction in speed can be realized with a minimal amount of the reverse curvature on the roundabout approach. The trajectory output files were then imported into the Surrogate Safety Assessment Model (SSAM) to determine the number and type of conflicts experienced at each approach under each scenario evaluated in AIMSUN.
Author: Agnimitra Sengupta Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Vulnerable road users (VRUs), such as pedestrians and bicyclists, are at a higher risk of being involved in crashes with motor vehicles, resulting in severe injuries or fatalities. Signalized intersections are a major safety concern for VRUs due to their complex and dynamic nature, highlighting the need to understand how these road users interact with motor vehicles and deploy evidence-based countermeasures to improve safety performance. Crashes involving VRUs are however infrequent, making it difficult to understand the underlying factors contributing to them. Therefore, identifying frequently observed potential conflicts is important to better understand and improve VRU safety at intersections. The Pennsylvania Department of Transportation (PennDOT) conducted a study using video-based event monitoring system to assess VRU and motor vehicle interactions at 15 signalized intersections across Pennsylvania to improve VRU safety performance. As a part of that study, automatic crash surrogates were generated from video data at 15 intersections in Pennsylvania. This research aims to assess the reliability of these automatically generated surrogates from the event monitoring system in predicting confirmed conflicts without human supervision using advanced data-driven models. The surrogate data used for analysis include relevant variables such as vehicular and VRU speeds, movements, post-encroachment time, signal states, lighting, and weather conditions. Findings highlight the varying importance and impact of specific surrogates in predicting true conflicts, with some being more informative than others. The differences between significant variables that help identify bicycle and pedestrian conflicts were also examined, revealing critical distinctions. The findings will assist transportation agencies in prioritizing infrastructure investments, such as bike lanes and crosswalks, and evaluating their effectiveness. Automatically detecting safety-critical events using video-based systems is a crucial step in developing smart infrastructure to enhance VRU safety. However, further research is needed to enhance its reliability and accuracy.
Author: Simon Washington Publisher: CRC Press ISBN: 0429520751 Category : Technology & Engineering Languages : en Pages : 496
Book Description
The book's website (with databases and other support materials) can be accessed here. Praise for the Second Edition: The second edition introduces an especially broad set of statistical methods ... As a lecturer in both transportation and marketing research, I find this book an excellent textbook for advanced undergraduate, Master’s and Ph.D. students, covering topics from simple descriptive statistics to complex Bayesian models. ... It is one of the few books that cover an extensive set of statistical methods needed for data analysis in transportation. The book offers a wealth of examples from the transportation field. —The American Statistician Statistical and Econometric Methods for Transportation Data Analysis, Third Edition offers an expansion over the first and second editions in response to the recent methodological advancements in the fields of econometrics and statistics and to provide an increasing range of examples and corresponding data sets. It describes and illustrates some of the statistical and econometric tools commonly used in transportation data analysis. It provides a wide breadth of examples and case studies, covering applications in various aspects of transportation planning, engineering, safety, and economics. Ample analytical rigor is provided in each chapter so that fundamental concepts and principles are clear and numerous references are provided for those seeking additional technical details and applications. New to the Third Edition Updated references and improved examples throughout. New sections on random parameters linear regression and ordered probability models including the hierarchical ordered probit model. A new section on random parameters models with heterogeneity in the means and variances of parameter estimates. Multiple new sections on correlated random parameters and correlated grouped random parameters in probit, logit and hazard-based models. A new section discussing the practical aspects of random parameters model estimation. A new chapter on Latent Class Models. A new chapter on Bivariate and Multivariate Dependent Variable Models. Statistical and Econometric Methods for Transportation Data Analysis, Third Edition can serve as a textbook for advanced undergraduate, Masters, and Ph.D. students in transportation-related disciplines including engineering, economics, urban and regional planning, and sociology. The book also serves as a technical reference for researchers and practitioners wishing to examine and understand a broad range of statistical and econometric tools required to study transportation problems.
Author: Nathaniel Patrick Edelmann Publisher: ISBN: Category : Traffic accidents Languages : en Pages : 0
Book Description
"Traffic safety may be analyzed with the use of surrogate safety measures, measures of safety that do not incorporate collision data but rather rely on the concept of traffic conflicts. Use of these measures provides several benefits over use of more traditional analysis methods with historical crash data. Surrogate measures eliminate the need to wait for crashes to occur to conduct a safety analysis. The amount of time required for enough crash data to accumulate can be significant, delaying safety analyses. Similarly, these measures allow for safety analysis to be conducted prior to crashes occurring, potentially calling attention to hazardous areas which may be altered to prevent crashes. In addition to these benefits, traffic conflicts occur much more frequently than collisions, generating many more data points which in turn make statistical methods of analysis more effective. Evaluating surrogate safety measures for a particular transportation network is most effectively done with the use of traffic microsimulation or with connected vehicle data. Traffic microsimulation (such as the use of PTV VISSIM) will generate kinematic data that may then be used for computation of surrogate safety measures. A significant amount of research has been done on this topic, resulting in the establishment of algorithms for calculation of several different surrogate measures and validation of these measures. Kinematic data from connected vehicles has also been used for the calculation of surrogate safety measures. One data point collected by connected vehicles is harsh braking events which could serve as a surrogate safety measure. Because drivers usually brake more gently if given the opportunity to do so, harsh braking events indicate that a traffic conflict has occurred or is about to occur. Such events take away the driver’s opportunity to brake gently. This research establishes statistical models which relate harsh braking events to crashes on intersections and segments in Salt Lake City, Utah. The findings indicate that harsh braking events have the effect of reducing expected crashes because they represent traffic conflicts which were remedied through the use of harsh braking as an evasive action. The presence of schools and the presence of left turn lanes were also found to be statistically significant crash predictors. In addition to this research work a paper outlining the existing state of safety analysis with surrogate safety measures and evaluating the usefulness and practicality of various existing measures is presented."--Boise State University ScholarWorks.
Author: Gary R. Consolazio Publisher: ISBN: Category : Curbs Languages : en Pages : 84
Book Description
The objectives of this study were to perform computer simulations of vehicle-curb and vehicle-berm impacts, to characterize the behavior of a wide range of vehicle types after such impacts, and to produce design and evaluation trajectory data for use by New Jersey Department of Transportation (NJDOT) engineers. The impact simulations performed involved a wide variety of vehicle types and several different curb and berm configurations (profiles) that are typical of those in use in the state of New Jersey. Simulation results from this research, primarily in the form of vehicle bumper trajectory plots, were produced to supplement existing curb-impact vehicle trajectory databases.
Author: Yousteena Bocktor
Author: Yousteena Bocktor
Author: Saroch Boonsiripant
Author: Shile Zhang
Author: European Conference of Ministers of Transport
Author: Kristin Kersavage
Author: Akshaey Sabhanayagam
Author: Agnimitra Sengupta
Author: Simon Washington
Author: Nathaniel Patrick Edelmann
Author: Gary R. Consolazio