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Evaluation of Cost-Effective Alternative Designs for Rural Expressway IntersectionsHoward, Jonathan 01 March 2022 (has links) (PDF)
Despite numerous studies demonstrating the effectiveness of Restricted Crossing U-Turn (RCUT) intersection design, its implementation remains uneven and close to zero in some large states such as California. This research provides a comprehensive framework to estimate the operational and safety performance of future RCUT designs in California. The framework is demonstrated for five intersections located on high-speed rural expressways in California using VISSIM microsimulation models to measure operational performance for each intersection including the base condition with the existing Two-Way Stop-Controlled (TWSC) intersection and two RCUT designs. To evaluate future safety performance, the microsimulation models were further utilized to compile vehicle trajectory data to use with the Surrogate Safety Assessment Model (SSAM) to develop a surrogate measure-based approach to estimating future safety performance. Detailed Intersection Control Evaluation (ICE) studies found that the RCUT was cost-effective and the preferred alternative. This framework may be applied to the analysis of locations where a RCUT intersection may be appropriate. The framework demonstrated here may be used by agencies to estimate the future benefits of the first-time application of treatments that have been successful elsewhere. Based on simulation results, the proposed RCUT designs reduced or eliminated the more severe crossing conflicts.
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Fatores de equivalência de veículos pesados em rodovias de pista dupla / Passenger-car equivalents for heavy vehicles on expresswaysPiva, Fernando José 19 June 2015 (has links)
Este trabalho visa avaliar o impacto de veículos pesados na qualidade de serviço de rodovias de pista dupla através de equivalentes veiculares. Para isso, foram feitas estimativas dos fatores de equivalência veicular em rodovias paulistas de pista dupla, com três ou mais faixas de tráfego em cada sentido. Essas estimativas foram obtidas a partir de dados empíricos coletados separadamente para cada faixa de tráfego, em intervalos de curta duração (5 ou 6 minutos). Foram utilizadas 53.655 observações, coletadas em oito estações de monitoramento, nos anos 2010 e 2011. O fator de equivalência foi calculado para cada intervalo através de uma equação obtida a partir do método de Huber, admitindo-se que a qualidade de serviço é a mesma para todas as faixas de tráfego naquele intervalo. Foi considerado como fluxo básico o da faixa da esquerda, nos intervalos em que são detectados apenas automóveis, e fluxo misto o da faixa da direita, em que passam automóveis e caminhões. Os resultados sugerem que: (1) em uma parte signicativa do tempo (52%), a qualidade de serviço não é a mesma em todas as faixas da rodovia; (2) o impacto marginal dos caminhões decresce à medida que a porcentagem de caminhões na corrente aumenta; e (3) as diferenças que existem no fator de equivalência em função do nível de serviço são menos evidentes em rampas mais íngremes, onde o efeito das limitações de desempenho dos caminhões é mais notado. A comparação deste estudo com outras duas pesquisas, em que foram utilizados dados gerados em simuladores de tráfego para estimar os fatores de equivalência, mostrou que as estimativas dos equivalentes veiculares obtidos usando dados empíricos são consistentemente maiores que as obtidas através de simulação. / The objective of this study is to evaluate the impact of heavy vehicles on the quality of service on Brazilian expressways (freeways and divided multilane highways), using passenger-car equivalents (PCEs) for heavy vehicles (trucks and buses). PCE estimates for expressways with three or more traffic lanes in each direction were obtained using traffic data collected over short time intervals (5 or 6 minutes) on expressways in the state of São Paulo. A total of 53,655 speed-flow observations, made at eight permanent trac sensor installations during 2010 and 2011, were used in this study. A PCE estimate was calculated for each time interval, using an equation derived from Huber\'s method, based on the assumption that the quality of service is the same across all traffic lanes during the time interval over which the traffic data is collected. Basic flow (passenger cars only) was assumed to be the observed traffic flow on the lane closest to the median, whereas mixed flow (passenger cars and heavy vehicles) was assumed to be the observed traffic flow on the lane closest to the shoulder. The results indicate that: (1) in a signicant portion of the time (52% of the observations) the quality of service is not the same across all traffic lanes; (2) the marginal impact of heavy vehicles decreases as the fraction of heavy vehicles in the traffic stream increases; and (3) the variations in PCE estimates due to the level of service are less evident on steeper grades, where the effect of heavy vehicles\' poorer performance is greater. PCE estimates obtained in this study were compared with PCEs obtained using simulation. The results indicate that PCE from empirical data are consistently higher than those estimated from simulation results.
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Relationship between traffic operations and road safety / Relações entre a operação de tráfego e segurança viáriaGustavo Riente de Andrade 18 December 2018 (has links)
Since before the release of the Highway Safety Manual research has been indicating the need to incorporate mobility and control aspects to road safety analysis. The first part of this work developed and implement in an existing computational engine a signal timing optimization method that considers mobility, safety, and emissions measures simultaneously. A sensitivity analysis was conducted to provide insight on the practical effects and order of relevance of 20 key input variables. Mobility improvement performance usually coincides with emissions improvements, but sometimes at the expense of safety. The second part of this work investigated the relationship between hourly traffic density and crash rates on Brazilian expressways with different characteristics, based on a database containing over 20,000 crashes and more than 35 million traffic volume observations and. The resulting curves for urban expressways follow a U shape, with minimum values associated with LOS B to C, while the relationships for rural expressways were found to be continuously increasing, suggesting that low volume rural roads are safer than the higher volume ones. The analysis of other influencing factors revealed that nighttime conditions, weaving segments and urban multilane highways could be related to higher crash rates. The third part of the project extends the analysis to crash severity modeling, using an ordered response choice model. The framework that better fit this database led to the development of two different models: single-vehicle crashes (SV) and multiple-vehicle crashes (MV), since the factors that explain the severity of crashes varies widely between these models. For instance, guardrails and barriers proved to effectively reduce severity for SV crashes, for which run-offs are the most severe crash type. The unique database used in this study also allowed for an investigation of the influence of prevailing traffic conditions on crash severity, while still controlling for all other factors. The results suggested that multiple-vehicle crash severity is negatively related with traffic density, while single-vehicle crashes are more closely related to speed. The findings of this work have implications to policy and design decisions, and the produced equation could be incorporated to active traffic management (ATM) and HCM reliability analysis. / Desde antes da publicação do Highway Safety Manual, vários pesquisadores indicam a necessidade de se incorporar aspectos de operação de tráfego à análise de segurança viária. A primeira parte deste trabalho desenvolveu e implementou em uma ferramenta computacional existente um método de otimização de tempos semafóricos que considera medidas de desempenho de operação, segurança e emissões simultaneamente. Uma análise de sensibilidade foi realizada para produzir conhecimento sobre os efeitos práticos e a ordem de relevância de 20 variáveis de entrada principais. O desempenho da programação semafórica em termos de redução dos atrasos geralmente coincide com redução das emissões, embora às vezes às custas da segurança. A segunda parte deste trabalho investigou a relação entre a densidade horária de tráfego e as taxas de acidentes em autoestradas e rodovias de pista dupla brasileiras com características diversas, com base em um banco de dados contendo mais de 20.000 registros de acidentes e mais de 35 milhões de observações de tráfego. As curvas resultantes para rodovias urbanas seguem um formato em U, com valores mínimos associados aos níveis de serviço B a C, enquanto que as relações para as rodovias rurais são contínuas e crescentes, sugerindo que rodovias rurais de baixo volume são mais seguras do que as de maior volume. A análise de outros fatores revelou que condições noturnas, segmentos de entrelaçamento e rodovias de pista dupla convencionais urbanas estariam relacionadas a maiores taxas de acidentes. A terceira parte deste projeto amplia a análise para modelagem de severidade dos acidentes, usando um modelo de escolha discreta ordenado. A estrutura que melhor se adequa a esse banco de dados levou ao desenvolvimento de dois modelos diferentes: acidentes com um veículo e acidentes com múltiplos veículos, já que os fatores que explicam a severidade dos acidentes variam muito entre esses modelos. Por exemplo, defensas e barreiras se mostraram efetivas para a redução da severidade de acidentes com um veículo, para as quais a saída de pista é o tipo de acidente mais grave. O amplo banco de dados usado neste estudo também permitiu uma investigação da influência das condições de tráfego na severidade do acidente, em comparação com todos os outros fatores. Os resultados sugeriram que a severidade de acidentes de múltiplos veículos está negativamente relacionada com a densidade de tráfego, enquanto colisões com um único veículo estão mais relacionadas à velocidade. As descobertas deste trabalho têm implicações nas decisões sobre políticas e projetos de transportes, e a equação produzida pode ser incorporada à análise de confiabilidade do gerenciamento ativo do tráfego (ATM) e do Highway Capacity Manual.
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Fatores de equivalência de veículos pesados em rodovias de pista dupla / Passenger-car equivalents for heavy vehicles on expresswaysFernando José Piva 19 June 2015 (has links)
Este trabalho visa avaliar o impacto de veículos pesados na qualidade de serviço de rodovias de pista dupla através de equivalentes veiculares. Para isso, foram feitas estimativas dos fatores de equivalência veicular em rodovias paulistas de pista dupla, com três ou mais faixas de tráfego em cada sentido. Essas estimativas foram obtidas a partir de dados empíricos coletados separadamente para cada faixa de tráfego, em intervalos de curta duração (5 ou 6 minutos). Foram utilizadas 53.655 observações, coletadas em oito estações de monitoramento, nos anos 2010 e 2011. O fator de equivalência foi calculado para cada intervalo através de uma equação obtida a partir do método de Huber, admitindo-se que a qualidade de serviço é a mesma para todas as faixas de tráfego naquele intervalo. Foi considerado como fluxo básico o da faixa da esquerda, nos intervalos em que são detectados apenas automóveis, e fluxo misto o da faixa da direita, em que passam automóveis e caminhões. Os resultados sugerem que: (1) em uma parte signicativa do tempo (52%), a qualidade de serviço não é a mesma em todas as faixas da rodovia; (2) o impacto marginal dos caminhões decresce à medida que a porcentagem de caminhões na corrente aumenta; e (3) as diferenças que existem no fator de equivalência em função do nível de serviço são menos evidentes em rampas mais íngremes, onde o efeito das limitações de desempenho dos caminhões é mais notado. A comparação deste estudo com outras duas pesquisas, em que foram utilizados dados gerados em simuladores de tráfego para estimar os fatores de equivalência, mostrou que as estimativas dos equivalentes veiculares obtidos usando dados empíricos são consistentemente maiores que as obtidas através de simulação. / The objective of this study is to evaluate the impact of heavy vehicles on the quality of service on Brazilian expressways (freeways and divided multilane highways), using passenger-car equivalents (PCEs) for heavy vehicles (trucks and buses). PCE estimates for expressways with three or more traffic lanes in each direction were obtained using traffic data collected over short time intervals (5 or 6 minutes) on expressways in the state of São Paulo. A total of 53,655 speed-flow observations, made at eight permanent trac sensor installations during 2010 and 2011, were used in this study. A PCE estimate was calculated for each time interval, using an equation derived from Huber\'s method, based on the assumption that the quality of service is the same across all traffic lanes during the time interval over which the traffic data is collected. Basic flow (passenger cars only) was assumed to be the observed traffic flow on the lane closest to the median, whereas mixed flow (passenger cars and heavy vehicles) was assumed to be the observed traffic flow on the lane closest to the shoulder. The results indicate that: (1) in a signicant portion of the time (52% of the observations) the quality of service is not the same across all traffic lanes; (2) the marginal impact of heavy vehicles decreases as the fraction of heavy vehicles in the traffic stream increases; and (3) the variations in PCE estimates due to the level of service are less evident on steeper grades, where the effect of heavy vehicles\' poorer performance is greater. PCE estimates obtained in this study were compared with PCEs obtained using simulation. The results indicate that PCE from empirical data are consistently higher than those estimated from simulation results.
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Relationship between traffic operations and road safety / Relações entre a operação de tráfego e segurança viáriaAndrade, Gustavo Riente de 18 December 2018 (has links)
Since before the release of the Highway Safety Manual research has been indicating the need to incorporate mobility and control aspects to road safety analysis. The first part of this work developed and implement in an existing computational engine a signal timing optimization method that considers mobility, safety, and emissions measures simultaneously. A sensitivity analysis was conducted to provide insight on the practical effects and order of relevance of 20 key input variables. Mobility improvement performance usually coincides with emissions improvements, but sometimes at the expense of safety. The second part of this work investigated the relationship between hourly traffic density and crash rates on Brazilian expressways with different characteristics, based on a database containing over 20,000 crashes and more than 35 million traffic volume observations and. The resulting curves for urban expressways follow a U shape, with minimum values associated with LOS B to C, while the relationships for rural expressways were found to be continuously increasing, suggesting that low volume rural roads are safer than the higher volume ones. The analysis of other influencing factors revealed that nighttime conditions, weaving segments and urban multilane highways could be related to higher crash rates. The third part of the project extends the analysis to crash severity modeling, using an ordered response choice model. The framework that better fit this database led to the development of two different models: single-vehicle crashes (SV) and multiple-vehicle crashes (MV), since the factors that explain the severity of crashes varies widely between these models. For instance, guardrails and barriers proved to effectively reduce severity for SV crashes, for which run-offs are the most severe crash type. The unique database used in this study also allowed for an investigation of the influence of prevailing traffic conditions on crash severity, while still controlling for all other factors. The results suggested that multiple-vehicle crash severity is negatively related with traffic density, while single-vehicle crashes are more closely related to speed. The findings of this work have implications to policy and design decisions, and the produced equation could be incorporated to active traffic management (ATM) and HCM reliability analysis. / Desde antes da publicação do Highway Safety Manual, vários pesquisadores indicam a necessidade de se incorporar aspectos de operação de tráfego à análise de segurança viária. A primeira parte deste trabalho desenvolveu e implementou em uma ferramenta computacional existente um método de otimização de tempos semafóricos que considera medidas de desempenho de operação, segurança e emissões simultaneamente. Uma análise de sensibilidade foi realizada para produzir conhecimento sobre os efeitos práticos e a ordem de relevância de 20 variáveis de entrada principais. O desempenho da programação semafórica em termos de redução dos atrasos geralmente coincide com redução das emissões, embora às vezes às custas da segurança. A segunda parte deste trabalho investigou a relação entre a densidade horária de tráfego e as taxas de acidentes em autoestradas e rodovias de pista dupla brasileiras com características diversas, com base em um banco de dados contendo mais de 20.000 registros de acidentes e mais de 35 milhões de observações de tráfego. As curvas resultantes para rodovias urbanas seguem um formato em U, com valores mínimos associados aos níveis de serviço B a C, enquanto que as relações para as rodovias rurais são contínuas e crescentes, sugerindo que rodovias rurais de baixo volume são mais seguras do que as de maior volume. A análise de outros fatores revelou que condições noturnas, segmentos de entrelaçamento e rodovias de pista dupla convencionais urbanas estariam relacionadas a maiores taxas de acidentes. A terceira parte deste projeto amplia a análise para modelagem de severidade dos acidentes, usando um modelo de escolha discreta ordenado. A estrutura que melhor se adequa a esse banco de dados levou ao desenvolvimento de dois modelos diferentes: acidentes com um veículo e acidentes com múltiplos veículos, já que os fatores que explicam a severidade dos acidentes variam muito entre esses modelos. Por exemplo, defensas e barreiras se mostraram efetivas para a redução da severidade de acidentes com um veículo, para as quais a saída de pista é o tipo de acidente mais grave. O amplo banco de dados usado neste estudo também permitiu uma investigação da influência das condições de tráfego na severidade do acidente, em comparação com todos os outros fatores. Os resultados sugeriram que a severidade de acidentes de múltiplos veículos está negativamente relacionada com a densidade de tráfego, enquanto colisões com um único veículo estão mais relacionadas à velocidade. As descobertas deste trabalho têm implicações nas decisões sobre políticas e projetos de transportes, e a equação produzida pode ser incorporada à análise de confiabilidade do gerenciamento ativo do tráfego (ATM) e do Highway Capacity Manual.
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A cidade em movimento: a via expressa e o pensamento urbanístico no século XX / The City in Motion: Expressway and Urbanistic Thinking in the Twentieth CenturyLuís Pompeo Martins 24 May 2017 (has links)
Este trabalho apresenta uma visão sobre a conceituação e o desenvolvimento tipológico das vias expressas urbanas durante a primeira metade do século XX. Partindo do entendimento das condições que determinaram a sua invenção para, em seguida, analisar o desenvolvimento técnico dessas infraestruturas nos campos da engenharia e do urbanismo. As promissoras possibilidades que as novas velocidades do automóvel ofereciam no início do século entraram imediatamente em conflito com a estrutura física, histórica e social da cidade tradicional. Para que fosse possível mediar tal embate, seria necessário um novo pacto social do uso da rua que segregasse pessoas e veículos, separando-os entre a calçada e o leito carroçável. É a partir da regulamentação do espaço viário dos centros urbanos - concebida pelos primeiros engenheiros de tráfego, nos Estados Unidos, entre as décadas de 1910 e 1920 - que a rua deixa de ser primordialmente espaço público para se tornar infraestrutura, dedicada ao transporte urbano de pedestres e motoristas. No entanto, a partir da década de 1930, devido ao crescimento dos acidentes de trânsito e dos congestionamentos, tornou-se necessário o desenvolvimento de um novo tipo de infraestrutura, que contemplasse as necessidades do carro, permitindo-lhe trafegar em velocidade com segurança. Era preciso construir um espaço absolutamente segregado, sem nenhum tipo de obstáculo, numa ruptura radical entre suas pistas e o restante da cidade. É dessa forma que surge a via segregada de acesso limitado - a via expressa -, um dos momentos mais contundentes da ideologia rodoviarista no espaço urbano, transformando radicalmente sua estrutura física e social. Ao longo do desenvolvimento da via expressa como tipologia por diversos profissionais, na primeira metade do século XX, sua relação com o espaço urbano é enfrentada de forma dialética. Enquanto algumas propostas negavam a cidade tradicional na sua busca por segregação através de novas formas de urbanismo, outras a enfrentaram, cortando a cidade com suas pistas, tornando os centros urbanos acessíveis ao automóvel. A partir da segunda metade do século XX, a síntese se estabelece. Ambas as formas de relação entre rodovia e cidade - de negação e enfrentamento - prosperam, tornando-se parte da realidade inexorável de uma nova condição urbana. Por fim, em contrapartida, a via expressa é analisada de forma abstrata, através da leitura de aspectos culturais, do conceito de \"progresso\" como um mito contemporâneo, bem como as noções de \"lugar\" e \"não-lugar\", à luz das condições impostas pela modernidade do capitalismo pós-industrial. / This paper presents a vision on the conceptualization and the typological development of urban expressways during the first half of the 20th century. Starting from the understanding of the conditions that determined its invention, and furtherly, analyzing the technical development of these infrastructures in the fields of engineering and urbanism. The promising possibilities offered by the automobile at the turn of the century immediately clashed with the physical, historical, and social structure of the traditional city. In order to mediate such a conflict, a new social pact regarding street use would be needed, managing the segregation between people and vehicles. In the United States, between the 1910s and 1920s, the street regulation conceived by the first traffic engineers transformed the public space of the street into infrastructure, dedicated almost exclusively to the urban transportation of Pedestrians and drivers. However, since the 1930s, due to the increase in traffic accidents and congestion, it became necessary to develop a new type of infrastructure, which would meet the needs of the car, allowing it to travel safely at a proper speed. It has become necessary the construction of an entirely segregated space to the car, rid of any kind of obstacle, in a radical rupture between its tracks and the rest of the city. The urban limited-access highway - also known as the \"expressway\" - emerges along this scenario, being one of the most striking moments of the car culture in urban space, radically transforming its physical and social structure. Throughout the development of the expressway as typology by several professionals, in the first half of the twentieth century, its relationship with urban space is dialectically confronted. While some proposals \"denied\" the traditional city through new forms of road design and urbanism, others \"confronted\" it, cutting through the city with its tracks, making urban centers accessible to the automobile. From the second half of the twentieth century, synthesis is established. Both forms of relationship between highway and city - of denial and confrontation - thrive, becoming part of the inexorable reality of a new urban condition. Finally, the expressway is analyzed in a more abstract approach, through the reading of some of its cultural aspects. The concept of \"progress\" as a contemporary myth is also mentioned, as well as the notions of \"place\" and \"non-place\", regarding the conditions imposed by the modernity of post-industrial capitalism.
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A cidade em movimento: a via expressa e o pensamento urbanístico no século XX / The City in Motion: Expressway and Urbanistic Thinking in the Twentieth CenturyMartins, Luís Pompeo 24 May 2017 (has links)
Este trabalho apresenta uma visão sobre a conceituação e o desenvolvimento tipológico das vias expressas urbanas durante a primeira metade do século XX. Partindo do entendimento das condições que determinaram a sua invenção para, em seguida, analisar o desenvolvimento técnico dessas infraestruturas nos campos da engenharia e do urbanismo. As promissoras possibilidades que as novas velocidades do automóvel ofereciam no início do século entraram imediatamente em conflito com a estrutura física, histórica e social da cidade tradicional. Para que fosse possível mediar tal embate, seria necessário um novo pacto social do uso da rua que segregasse pessoas e veículos, separando-os entre a calçada e o leito carroçável. É a partir da regulamentação do espaço viário dos centros urbanos - concebida pelos primeiros engenheiros de tráfego, nos Estados Unidos, entre as décadas de 1910 e 1920 - que a rua deixa de ser primordialmente espaço público para se tornar infraestrutura, dedicada ao transporte urbano de pedestres e motoristas. No entanto, a partir da década de 1930, devido ao crescimento dos acidentes de trânsito e dos congestionamentos, tornou-se necessário o desenvolvimento de um novo tipo de infraestrutura, que contemplasse as necessidades do carro, permitindo-lhe trafegar em velocidade com segurança. Era preciso construir um espaço absolutamente segregado, sem nenhum tipo de obstáculo, numa ruptura radical entre suas pistas e o restante da cidade. É dessa forma que surge a via segregada de acesso limitado - a via expressa -, um dos momentos mais contundentes da ideologia rodoviarista no espaço urbano, transformando radicalmente sua estrutura física e social. Ao longo do desenvolvimento da via expressa como tipologia por diversos profissionais, na primeira metade do século XX, sua relação com o espaço urbano é enfrentada de forma dialética. Enquanto algumas propostas negavam a cidade tradicional na sua busca por segregação através de novas formas de urbanismo, outras a enfrentaram, cortando a cidade com suas pistas, tornando os centros urbanos acessíveis ao automóvel. A partir da segunda metade do século XX, a síntese se estabelece. Ambas as formas de relação entre rodovia e cidade - de negação e enfrentamento - prosperam, tornando-se parte da realidade inexorável de uma nova condição urbana. Por fim, em contrapartida, a via expressa é analisada de forma abstrata, através da leitura de aspectos culturais, do conceito de \"progresso\" como um mito contemporâneo, bem como as noções de \"lugar\" e \"não-lugar\", à luz das condições impostas pela modernidade do capitalismo pós-industrial. / This paper presents a vision on the conceptualization and the typological development of urban expressways during the first half of the 20th century. Starting from the understanding of the conditions that determined its invention, and furtherly, analyzing the technical development of these infrastructures in the fields of engineering and urbanism. The promising possibilities offered by the automobile at the turn of the century immediately clashed with the physical, historical, and social structure of the traditional city. In order to mediate such a conflict, a new social pact regarding street use would be needed, managing the segregation between people and vehicles. In the United States, between the 1910s and 1920s, the street regulation conceived by the first traffic engineers transformed the public space of the street into infrastructure, dedicated almost exclusively to the urban transportation of Pedestrians and drivers. However, since the 1930s, due to the increase in traffic accidents and congestion, it became necessary to develop a new type of infrastructure, which would meet the needs of the car, allowing it to travel safely at a proper speed. It has become necessary the construction of an entirely segregated space to the car, rid of any kind of obstacle, in a radical rupture between its tracks and the rest of the city. The urban limited-access highway - also known as the \"expressway\" - emerges along this scenario, being one of the most striking moments of the car culture in urban space, radically transforming its physical and social structure. Throughout the development of the expressway as typology by several professionals, in the first half of the twentieth century, its relationship with urban space is dialectically confronted. While some proposals \"denied\" the traditional city through new forms of road design and urbanism, others \"confronted\" it, cutting through the city with its tracks, making urban centers accessible to the automobile. From the second half of the twentieth century, synthesis is established. Both forms of relationship between highway and city - of denial and confrontation - thrive, becoming part of the inexorable reality of a new urban condition. Finally, the expressway is analyzed in a more abstract approach, through the reading of some of its cultural aspects. The concept of \"progress\" as a contemporary myth is also mentioned, as well as the notions of \"place\" and \"non-place\", regarding the conditions imposed by the modernity of post-industrial capitalism.
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Traffic Safety Assessment of Different Toll Collection Systems on Expressways Using Multiple Analytical TechniquesAbuzwidah, Muamer 01 January 2014 (has links)
Traffic safety has been considered one of the most important issues in the transportation field. Crashes have caused extensive human and economic losses. With the objective of reducing crash occurrence and alleviating crash injury severity, major efforts have been dedicated to reveal the hazardous factors that affect crash occurrence. With these consistent efforts, both fatalities and fatality rates from road traffic crashes in many countries have been steadily declining over the last ten years. Nevertheless, according to the World Health Organization, the world still lost 1.24 million lives from road traffic crashes in the year of 2013. And without action, traffic crashes on the roads network are predicted to result in deaths of around 1.9 million people, and up to 50 million more people suffer non-fatal injuries annually, with many incurring a disability as a result of their injury by the year 2020. To meet the transportation needs, the use of expressways (toll roads) has risen dramatically in many countries in the past decade. In fact, freeways and expressways are considered an important part of any successful transportation system. These facilities carry the majority of daily trips on the transportation network. Although expressways offer high level of service, and are considered the safest among other types of roads, traditional toll collection systems may have both safety and operational challenges. The traditional toll plazas still experience many crashes, many of which are severe. Therefore, it becomes more important to evaluate the traffic safety impacts of using different tolling systems. The main focus of the research in this dissertation is to provide an up-to-date safety impact of using different toll collection systems, as well as providing safety guidelines for these facilities to promote safety and enhance mobility on expressways. In this study, an extensive data collection was conducted that included one hundred mainline toll plazas located on approximately 750 miles of expressways in Florida. Multiple sources of data available online maintained by Florida Department of Transportation were utilized to identify traffic, geometric and geographic characteristics of the locations as well as investigating and determination of the most complete and accurate data. Different methods of observational before-after and Cross-Sectional techniques were used to evaluate the safety effectiveness of applying different treatments on expressways. The Before-After method includes Naive Before-After, Before-After with Comparison Group, and Before-After with Empirical Bayesian. A set of Safety Performance Functions (SPFs) which predict crash frequency as a function of explanatory variables were developed at the aggregate level using crash data and the corresponding exposure and risk factors. Results of the aggregate traffic safety analysis can be used to identify the hazardous locations (hot spots) such as traditional toll plazas, and also to predict crash frequency for untreated sites in the after period in the Before-After with EB method or derive Crash Modification Factors (CMF) for the treatment using the Cross-Sectional method. This type of analysis is usually used to improve geometric characteristics and mainly focus on discovering the risk factors that are related to the total crash frequency, specific crash type, and/or different crash severity levels. Both simple SPFs (with traffic volume only as an explanatory variable) and full SPFs (with traffic volume and additional explanatory variable(s)) were used to estimate the CMFs and only CMFs with lower standard error were recommended. The results of this study proved that safety effectiveness was significantly improved across all locations that were upgraded from Traditional Mainline Toll Plazas (TMTP) to the Hybrid Mainline Toll Plazas (HMTP) system. This treatment significantly reduced total, Fatal-and-Injury (F+I), and Rear-End crashes by 47, 46 and 65 percent, respectively. Moreover, this study examined the traffic safety impact of using different designs, and diverge-and-merge areas of the HMTP. This design combines either express Open Road Tolling (ORT) lanes on the mainline and separate traditional toll collection to the side (design-1), or traditional toll collection on the mainline and separate ORT lanes to the side (design-2). It was also proven that there is a significant difference between these designs, and there is an indication that design-1 is safer and the majority of crashes occurred at diverge-and-merge areas before and after these facilities. However, design-2 could be a good temporary design at locations that have low prepaid transponder (Electronic Toll Collection (ETC)) users. In other words, it is dependent upon the percentage of the ETC users. As this percentage increases, more traffic will need to diverge and merge; thus, this design becomes riskier. In addition, the results indicated significant relationships between the crash frequency and toll plaza types, annual average daily traffic, and drivers* age. The analysis showed that the conversion from TMTP to the All-Electronic Toll Collection (AETC) system resulted in an average reduction of 77, 76, and 67 percent for total, F+I, and Property Damage Only (PDO) crashes, respectively; for rear end and Lane Change Related (LCR) crashes the average reductions were 81 and 75 percent, respectively. The conversion from HMTP to AETC system enhanced traffic safety by reducing crashes by an average of 23, 29 and 19 percent for total, F+I, and PDO crashes; also, for rear end and LCR crashes, the average reductions were 15 and 21 percent, respectively. Based on these results, the use of AETC system changed toll plazas from the highest risk sections on Expressways to be similar to regular segments. Therefore, it can be concluded that the use of AETC system was proven to be an excellent solution to several traffic operations as well as environmental and economic problems. For those agencies that cannot adopt the HMTP and the AETC systems, improving traffic safety at traditional toll plazas should take a priority. This study also evaluates the safety effectiveness of the implementation of High-Occupancy Toll lanes (HOT Lanes) as well as adding roadway lighting to expressways. The results showed that there were no significant impact of the implementation of HOT lanes on the roadway segment as a whole (HOT and Regular Lanes combined). But there was a significant difference between the regular lanes and the HOT lanes at the same roadway segment; the crash count increased at the regular lanes and decreased at the HOT lanes. It was found that the total and F+I crashes were reduced at the HOT lanes by an average of 25 and 45 percent, respectively. This may be attributable to the fact that the HOT lanes became a highway within a highway. Moreover adding roadway lighting has significantly improved traffic safety on the expressways by reducing the night crashes by approximately 35 percent. Overall, the proposed analyses of the safety effectiveness of using different toll collection systems are useful in providing expressway authorities with detailed information on where countermeasures must be implemented. This study provided for the first time an up-to-date safety impact of using different toll collection systems, also developed safety guidelines for these systems which would be useful for practitioners and roadway users.
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