A study was done to explore the suitability of intersection and arterial collision prediction models based on traffic conflicts, generated using the Paramics microsimulation suite and the Surrogate Safety Assessment Model (SSAM). A linear regression model and a generalized linear model with a negative binomial error structure were explored to correlate conflicts to crash rates, as well as the conflict-based models suggested by SSAM. The model predictions were compared to volume-based predictions and historical data from Toronto, Ontario, Canada. The volume- based predictions were calculated using a negative binomial generalized linear model, fitted to the same arterial and intersection sets used to fit the conflict-based models. The results show the predictions generated by a conflict-based model were comparable for intersections, but poor for arterials.

A study was done to explore the suitability of intersection and arterial collision prediction models based on traffic conflicts, generated using the Paramics microsimulation suite and the Surrogate Safety Assessment Model (SSAM). A linear regression model and a generalized linear model with a negative binomial error structure were explored to correlate conflicts to crash rates, as well as the conflict-based models suggested by SSAM. The model predictions were compared to volume-based predictions and historical data from Toronto, Ontario, Canada. The volume- based predictions were calculated using a negative binomial generalized linear model, fitted to the same arterial and intersection sets used to fit the conflict-based models. The results show the predictions generated by a conflict-based model were comparable for intersections, but poor for arterials.

Traffic safety has traditionally been measured by analyzing historical accident data, which is a reactive method where a certain number of accidents must occur in order to identify the safety problem. An alternative safety assessment method is to use proximal safety indicators that are defined as measures of accident proximity, which is considered a proactive method. With this method it is possible to detect the safety problem before the accidents have happened. To be able to detect problems in traffic situations in general, microscopic simulation is commonly used. In these models it may be possible to generate representative near-accidents, measured by proximal safety indicator techniques. A benefit of this would be the possibility to experiment with different road designs and evaluate the traffic safety level before reconstructions of the road infrastructure. Therefore has an investigation been performed to test the possibility to identify near-accidents (conflicts) in a microscopic simulation model mimicking the Traffic Conflict Technique developed by Hydén (1987). In order to perform the investigation a case study has been used where an intersection in the city center of Stockholm was studied. The intersection has been rebuilt, which made it possible to perform a before and after study. For the previous design there was a traffic safety assessment available which was carried out using the Traffic Conflict Technique. Microscopic simulation models representing the different designs of the intersection were built in PTV Vissim. In order to evaluate and measure the traffic safety in reality as well as in the microscopic simulation models, a traffic safety assessment was performed in each case. The traffic safety assessment in field for the present design was carried out as a part of this thesis. The main focus of this thesis was the road safety for vulnerable road users. The method to identify conflicts in the simulation model has been to extract raw data output from the simulation model and thereafter process this data in a Matlab program, aiming to mimic the Traffic Conflict Technique. The same program and procedure was used for both the previous and the present design of the intersection. The results from the traffic safety assessment in the simulation model have been compared to the results from the field study in order to evaluate how well microscopic simulation works as an evaluation tool for traffic safety in new designs. The comparison shows that the two methods of conflict identification cannot replace each other straight off. But with awareness of the differences between the methods, the simulation model could be used as an indication when evaluating the level of traffic safety in a road design.

Esta pesquisa propõe um método que compara o desempenho de interseções através de quatro medidas: número de conflitos de tráfego, capacidade integral de processamento, atraso e espera média e custo de construção. O método foi aplicado a um grupo de seis interseções, três configurações alternativas e três variações do conceito trevo vazado, conceito básico adotado na grande maioria das interseções em nível de rodovias rurais brasileiras. Em paralelo, desenvolveu-se um método de conflitos baseado no conceito de conflito equivalente. O programa INTEGRATION foi utilizado no cálculo da capacidade integral de processamento e atraso e espera média. É apresentada uma planilha simplificada de custo de construção para obtenção dos orçamentos das interseções. Uma comparação de desempenhos é realizada para uma condição particular de capacidade de tráfego. Como o método permite a parametrização, ele pode também ser utilizado para avaliar outras condições operacionais. Conclui-se que, para as condições operacionais avaliadas, as configurações do tipo trevo vazado tem desempenho inferior a duas alternativas investigadas na pesquisa, a rotatória e a rotatória alongada com entrelaçamento. / This research proposes a method to compare road intersection performances through four measures: number of traffic conflicts, processing integral capacity, average delay and waiting time and construction cost. The method was applied to a group of six intersections, three alternative configurations of intersections and three variations of the \"trevo vazado\" concept, which is usual basic concept for projects of Brazilian road intersection. At the same time, a traffic conflict method, based on equivalent conflict concept, was developed. The INTEGRATION software was used to calculate the processing integral capacity and the average delays and waiting times. A simple construction cost table for estimating the construction cost of the intersections is presented. A performance comparison of the various intersection configurations is also presented for a particular level of processing capacity. As the method permits parametrization, it can be used to evaluate other operational conditions. It is concluded that, for the evaluated operational conditions, the configurations of the \"trevo vazado\" have an inferior performance than the roundabout and the along roundabout.

Esta pesquisa propõe um método que compara o desempenho de interseções através de quatro medidas: número de conflitos de tráfego, capacidade integral de processamento, atraso e espera média e custo de construção. O método foi aplicado a um grupo de seis interseções, três configurações alternativas e três variações do conceito trevo vazado, conceito básico adotado na grande maioria das interseções em nível de rodovias rurais brasileiras. Em paralelo, desenvolveu-se um método de conflitos baseado no conceito de conflito equivalente. O programa INTEGRATION foi utilizado no cálculo da capacidade integral de processamento e atraso e espera média. É apresentada uma planilha simplificada de custo de construção para obtenção dos orçamentos das interseções. Uma comparação de desempenhos é realizada para uma condição particular de capacidade de tráfego. Como o método permite a parametrização, ele pode também ser utilizado para avaliar outras condições operacionais. Conclui-se que, para as condições operacionais avaliadas, as configurações do tipo trevo vazado tem desempenho inferior a duas alternativas investigadas na pesquisa, a rotatória e a rotatória alongada com entrelaçamento. / This research proposes a method to compare road intersection performances through four measures: number of traffic conflicts, processing integral capacity, average delay and waiting time and construction cost. The method was applied to a group of six intersections, three alternative configurations of intersections and three variations of the \"trevo vazado\" concept, which is usual basic concept for projects of Brazilian road intersection. At the same time, a traffic conflict method, based on equivalent conflict concept, was developed. The INTEGRATION software was used to calculate the processing integral capacity and the average delays and waiting times. A simple construction cost table for estimating the construction cost of the intersections is presented. A performance comparison of the various intersection configurations is also presented for a particular level of processing capacity. As the method permits parametrization, it can be used to evaluate other operational conditions. It is concluded that, for the evaluated operational conditions, the configurations of the \"trevo vazado\" have an inferior performance than the roundabout and the along roundabout.

This study adopted the traffic conflict technique, investigated and applied it for evaluation of freeway weaving section safety performance. Conflicts between vehicles were identified based on the state of interactions between vehicles in the traffic stream at microscopic level. The VISSIM microscopic simulation model was employed to simulate traffic operation. Surrogate safety measures were formulated based on deceleration rate required to avoid crash and these simulation-based measures were statistically compared and validated using crash data collected from the same study site. Three study sites located in Houston and Dallas areas were selected. Geometric and traffic data were collected using various technique including the use of traffic surveillance cameras and pneumatic tubes. The study revealed the existence of links between actually observed crashes and the surrogate safety measures. The study findings support the possible the use of microscopic simulation to evaluate safety performance of weaving areas and other transportation facilities.

<p dir="ltr">In 2021, the U.S. experienced over 45,000 road accident fatalities and approximately two million injuries, resulting in both emotional trauma and tangible economic impact. Road safety management traditionally depends on crash data, which though invaluable, is reactive, takes a long time to aggregate and has certain limitations. Traffic conflicts, the most used surrogate measure, promises to enhance road safety estimation without the drawbacks of crash data using a short amount of data collection.</p><p dir="ltr">After decades of debate, a definition for traffic conflicts that can be practically applied (Tarko, 2018, 2021) and a bridge method to estimate number of crashes given conflicts (Tarko, 2018) have emerged. The predictive validity of the bridge method has been successfully demonstrated for naturalistic driving data using a framework to extract conflicts (Tarko & Lizarazo, 2021). The only hurdle remaining for adoption of traffic conflicts to estimate safety at a given location is a means to record trajectories of all road users at that location.</p><p dir="ltr">Traditionally, video cameras and associated image processing techniques have been used to track road users at a given location. Cameras capture a 2D projection of the 3D world, therefore incur a loss of information and cameras are sensitive to ambient light conditions.</p><p dir="ltr">Over the past decade, LiDARs have emerged as an alternative to cameras for tracking road users. The advantage of LiDARs is that they record 3D information directly and are insensitive to ambient light conditions. Furthermore, they are less affected by adverse weather conditions than cameras. Spurred by the adoption by autonomous vehicle manufacturers, LiDAR sensors are projected to achieve cost parity with cameras over the next several years.</p><p dir="ltr">This dissertation explores the various aspects of LiDAR based tracking starting with sensor selection. The simulation work done shows the advantage of a multi-LiDAR setup in effectively covering an intersection. A novel self-aligning procedure to achieve spatial congruity proposed is shown to outperform the state of the art.</p><p dir="ltr">New methods for identifying and removing background points that work even under moderate congestion have been proposed. New methods for clustering the non-background points and estimating a bounding box with proper orientation are proposed. The results of the experiments show that they work better than the corresponding state of the art methods. The rest of the processing follows the framework introduced by (Bandaru, 2016).</p><p dir="ltr">A thorough evaluation of positional accuracy, orientation accuracy and accuracy of estimated vehicle dimensions has been undertaken using data from an instrumented vehicle acting as ground truth to prove that the trajectories generated are of sufficient quality to identify traffic conflicts.</p><p dir="ltr">Further, the framework proposed by (Lizarazo, 2020) has been adopted to identify traffic encounters from the trajectories obtained. A new method to select an alternative trajectory for a vehicle exhibiting an evasive maneuver, used in the counterfactual analysis to estimate time to collision is proposed. Data collected at three different intersections using a LiDAR are processed to extract trajectories and the framework is applied to identify safety relevant events. The spatial distribution of the identified events is compared against the spatial distribution of crashes.</p><p dir="ltr">While the spatial distribution shows promise, the actual number of claimed conflicts was too low. The rare nature of failure caused traffic conflict that can be linked to crashes could be a reason. A more permanent installation is suggested to ascertain the duration required to observe sufficient number of traffic conflicts, that could be used to reliably estimate crashes.</p><p dir="ltr"><b>References:</b></p><p dir="ltr">Bandaru, V. K. (2016). Algorithms for LiDAR Based Traffic Tracking: Development and Demonstration. <i>Open Access Theses</i>. https://docs.lib.purdue.edu/open_access_theses/922</p><p dir="ltr">Lizarazo, C. (2020). <i>Identification Of Failure-Caused Traffic Conflicts in Tracking Systems: A General Framework</i> [PhD Thesis]. Purdue University.</p><p dir="ltr">Tarko, A. (2018). Estimating the expected number of crashes with traffic conflicts and the Lomax Distribution–A theoretical and numerical exploration. <i>Accident Analysis & Prevention</i>, <i>113</i>, 63–73.</p><p dir="ltr">Tarko, A. (2021). A unifying view on traffic conflicts and their connection with crashes. <i>Accident Analysis & Prevention</i>, <i>158</i>, 106187. https://doi.org/10.1016/j.aap.2021.106187</p><p dir="ltr">Tarko, A., & Lizarazo, C. (2021). Validity of failure-caused traffic conflicts as surrogates of rear-end collisions in naturalistic driving studies. <i>Accident Analysis & Prevention</i>, <i>149</i>, 105863.</p>

Este trabalho contém uma revisão bibliográfica atualizada acerca do tema segurança viária; um diagnóstico da situação atual da gestão da segurança viária em Marília e um elenco de ações propostas para a melhoria dessa gestão; um estudo dos acidentes de trânsito ocorridos na cidade, contemplando a identificação dos pontos críticos, a análise das causas dos acidentes à luz das informações contidas nos boletins da ocorrência policial e a apresentação de propostas de ações para redução dos acidentes nesses locais, elaboradas com base em auditorias no campo. Algumas das ações propostas para a melhoria da segurança viária na cidade de Marília são: criação de um órgão específico da Prefeitura para fazer a gestão do trânsito na cidade (incluindo a segurança); implementação de um banco de dados de acidentes informatizado; investimentos nas áreas de Educação e Esforço Legal, utilização da técnica de análise de conflitos de tráfego e de auditoria de campo de forma rotineira pelo órgão gestor, aperfeiçoamento do preenchimento dos boletins de ocorrência de acidentes, através de treinamento dos policiais e eventuais alterações de conteúdo; etc. / This work contains: a bibliographical revision brought up to date concerning the subject road safety; a diagnosis of the current situation of the management of the road safety in Marília and proposal of actions for the improvement of this management; and a study of the traffic accidents occurred in the city, contemplating the identification of the critical points, the analysis of the causes of the accidents based in bulletins of occurrence and some proposals for to reduce the accidents rates in those places based on field auditorships. Some of the actions proposals for the improvement of the road security in the city of Marília are: creation of a specific agency of the City hall to make the management in the transit in the city; implementation of a computerized data base; investment in the area of Education and Efforcement; use ofthe technique of analysis of traffic conflicts and audit of field of routine form for the managing agency; perfectioning of the fulfilling of accident reports, through training of the policemen and eventual alterations the format; etc.

Este trabalho contém uma revisão bibliográfica atualizada acerca do tema segurança viária; um diagnóstico da situação atual da gestão da segurança viária em Marília e um elenco de ações propostas para a melhoria dessa gestão; um estudo dos acidentes de trânsito ocorridos na cidade, contemplando a identificação dos pontos críticos, a análise das causas dos acidentes à luz das informações contidas nos boletins da ocorrência policial e a apresentação de propostas de ações para redução dos acidentes nesses locais, elaboradas com base em auditorias no campo. Algumas das ações propostas para a melhoria da segurança viária na cidade de Marília são: criação de um órgão específico da Prefeitura para fazer a gestão do trânsito na cidade (incluindo a segurança); implementação de um banco de dados de acidentes informatizado; investimentos nas áreas de Educação e Esforço Legal, utilização da técnica de análise de conflitos de tráfego e de auditoria de campo de forma rotineira pelo órgão gestor, aperfeiçoamento do preenchimento dos boletins de ocorrência de acidentes, através de treinamento dos policiais e eventuais alterações de conteúdo; etc. / This work contains: a bibliographical revision brought up to date concerning the subject road safety; a diagnosis of the current situation of the management of the road safety in Marília and proposal of actions for the improvement of this management; and a study of the traffic accidents occurred in the city, contemplating the identification of the critical points, the analysis of the causes of the accidents based in bulletins of occurrence and some proposals for to reduce the accidents rates in those places based on field auditorships. Some of the actions proposals for the improvement of the road security in the city of Marília are: creation of a specific agency of the City hall to make the management in the transit in the city; implementation of a computerized data base; investment in the area of Education and Efforcement; use ofthe technique of analysis of traffic conflicts and audit of field of routine form for the managing agency; perfectioning of the fulfilling of accident reports, through training of the policemen and eventual alterations the format; etc.

The purpose of this study is to compare the safety of cyclists in five bicycle facility layouts in signalized intersections at various traffic volumes in order to assess if some layouts are better than others with regards to cyclist safety and to develop methods to facilitate this comparison. The five layouts included two full-length bicycle tracks with and without separate right-turning lane, two truncated bicycle tracks – one in which cyclists and right-turning vehicles merge in the right-turning lane, one continued into a narrow bicycle lane – and a recessed bicycle track. Using two different definitions of traffic conflicts the safety of cyclists in each layout is calculated as the risk of a cyclist being involved in a conflict with left- and right-turning vehicles at low, medium and high vehicle volumes, respectively. In total, around 35,500 left-turning vehicles, 38,000 right-turning vehicles and 16,000 cyclists going straight ahead were observed, resulting in 12 left-hook and 25 right-hook traffic conflicts for the reaction-based indicator and 25 left-hook and 80 right-hook traffic conflicts for the time-based indicator. The results show that regardless of which of the two conflict indicators were used, the number of conflicts was too small to make firm conclusions about which layout is safest for cyclists at various traffic volumes, although the study was based on 80 h of video recordings from each of the five intersections. However, a recessed bicycle track seems to be safer than the other geometric layouts. In order to facilitate the detection of conflicts, we developed watchdog video analysis software to reduce the amount of video. This software compressed 400 h of video into 64 h, i.e. 16% of its original length. The use of this software is particularly important to provide enough conflicts for an analysis if even larger traffic conflict studies should be carried out.