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Highway safety has been a priority for many years now. A system-wide crash analysis is a practical solution when only a limited budget is available for improving safety of highways. A systematic approach, in contrast to a hotspot analysis, allows for a widespread installation of lower-cost countermeasures across the highway network. This study focuses on the safety evaluation of a particular facility type, urban freeway off-ramps, in terms of its geometric and traffic characteristics. 144 off-ramp segments in Richmond, VA were evaluated based on the crash data available from 2011 to 2015. A statistical model was developed that relates crashes to the geometric and traffic characteristics of each off-ramp segment. A test for independence was performed to identify if a statistically significant difference existed between type of collision and severity of crashes with respect to ramp geometry and traffic control. Significant geometric and traffic variables were then identified from the model and independence test to assist in the selection of low-cost countermeasures. AADTs of both freeways and off-ramps were found to be the most statistically significant variables. Installation of advance warning signs for better traffic management near the freeway diverge area and clearing roadsides of fixed objects to reduce rear-end collisions are low-cost solutions for crashes on urban off-ramps in the study area. The results of this study demonstrate an approach to safety evaluations that could support transportation planners and agencies in identifying system-wide locations to install or apply appropriate low-cost countermeasures. / Master of Science

The dissertation develops analytical models that estimate the capacity of freeway weaving sections. The analytical models are developed using simulated data that were compiled using the INTEGRATION software. Consequently, the first step of the research effort is to validate the INTEGRATION lane-changing modeling procedures and the capacity estimates that are derived from the model against field observations. The INTEGRATION software is validated against field data gathered by the University of California at Berkeley by comparing the lateral and longitudinal distribution of simulated and field observed traffic volumes categorized by O-D pair on nine weaving sections in the Los Angeles area. The results demonstrate a high degree of consistency between simulated and field observed traffic volumes within the various weaving sections. Subsequently, the second validation effort compares the capacity estimates of the INTEGRATION software to field observations from four weaving sections operating at capacity on the Queen Elizabeth Way (QEW) in Toronto, Canada. Again, the results demonstrate that the capacity estimates of the INTEGRATION software are consistent with the field observations both in terms of absolute values and temporal variability across different days. The error was found to be in the range of 10% between simulated and field observed capacities. Prior to developing the analytical models, the dissertation presents a systematic analysis of the factors that impact the capacity of freeway weaving sections, which were found to include the length of the weaving section, the weaving ratio (a new parameter that is developed as part of this research effort), the percentage of heavy vehicles, and the speed limit differential between freeway and on- and off-ramps. The study demonstrates that the weaving ratio, which is currently defined as the ratio of the lowest weaving volume to the total weaving volume in the 2000 Highway Capacity Manual, has a significant impact on the capacity of weaving sections. The study also demonstrates that the weaving ratio is an asymmetric function and thus should reflect the source of the weaving volume. Consequently, a new definition for the weaving ratio is introduced that explicitly identifies the source of the weaving volume. In addition, the study demonstrates that the length of the weaving section has a larger impact on the capacity of weaving sections for short lengths and high traffic demands. Furthermore, the study demonstrates that there does not exist enough evidence to conclude that the speed limit differential between mainline freeway and on- and off-ramps has a significant impact on weaving section capacities. Finally, the study demonstrates that the HCM procedures model the heavy duty vehicle impacts reasonably well. This dissertation presents the development of new capacity models for freeway weaving sections. In these models, a new definition of the weaving ratio that explicitly accounts for the source of weaving volume is introduced. The proposed analytical models estimate the capacity of weaving sections to within 12% of the simulated data, while the HCM procedures exhibit errors in the range of 114%. Among the newly developed models, the Artificial Neural Network (ANN) models performs slightly better that the statistical models in terms of model prediction errors. However, the sensitivity analysis results demonstrate unrealistic behavior of the ANN models under certain conditions. Consequently, the use of a statistical model is recommended because it provides a high level of accuracy while providing accurate model responses to changes in model input parameters (good response to the gradient of the input parameters). / Ph. D.

The Bay Area Metropolitan Transportation Commission’s (MTC) Freeway Service Patrol’s highway motorist response service is reporting a reduction in their service levels. We analyze the relationship between the reduction in the Bay Area Freeway Service Patrol’s (FSP) motorist assists and changes in vehicle miles traveled (VMT), California Highway Patrol (CHP) reported incidents, and cover research on the impact of new and old vehicle fleet turnover. VMT and CHP incidents have differential effects on FSP assists. Although incidents occurring on freeways with high traffic flows tend to cause more congestion, the trend in local VMT along Bay Area freeway corridors does not share a strong correlation with FSP assists. Through a chi-square test, bivariate correlation and cross tabulation, we can see a relationship and pattern between FSP assists, incidents and VMT. Further analysis into the dispersion of assists, incidents and VMT show that the distribution of the FSP assists over CHP reported incidents is not perfectly equal. By analyzing VMT, CHP reported incidents and research around new vehicle fleet turnover affecting FSP assisted-incidents, Metropolitan Transportation Commission staff can systematically improve the FSP operational model; strategize ways to improve service on needier freeway corridors, while reducing unnecessary service in other regions.

The Road Ranger program is a freeway service patrol (FSP) designed to assist disabled vehicles along congested freeway segments and relieve peak period non-recurring congestion through quick detection, verification and removal of freeway incidents in Florida. It consists of approximately 88 vehicles in fleet and provides free service to about 918 centerline miles. The program is funded by the Florida Department of Transportation (FDOT) and its partners, and is bid out to private contractors. The objective of this study is to examine and evaluate the benefits of the Road Ranger service against their operating costs in five of the seven FDOT Districts and Florida Turnpike Enterprise. The five Districts were chosen due to the availability of Road Ranger program data and activity logs for analysis. The Road Ranger program provides direct benefits to the general public in terms of reduced delay, fuel consumption, air pollution and improved safety and security. The benefits would be expected to be more significant during the peak period when demand reaches or exceeds capacity than in the off-peak and the mid-day period where capacity may not be as significant an issue. The costs considered in this analysis include costs of administration, operation, maintenance, employee salaries, and overhead costs. Incident data were obtained from the daily logs maintained by the Road Ranger service provider containing important information about the time, duration, location, and type of service provided. Other data collected for this study include average daily traffic volume, geometric characteristics of the freeways, unit cost of Road Ranger service, etc. The Freeway Service Patrol Evaluation (FSPE) model developed by the University of California-Berkley was calibrated and used to estimate the benefit-cost ratio for the Road Ranger program. The estimated benefit/cost ratios based on delay and fuel savings indicate that the Road Ranger program produces significant benefits in all the five Districts and Turnpike. The range of benefit-cost ratio of the Road Ranger program in different districts is from 2.3:1 to 41.5:1. The benefit -cost ratio of the entire Road Ranger program is estimated to be in excess of 25:1.

abstract: The role of environmental factors that influence atmospheric propagation of sound originating from freeway noise sources is studied with a combination of field experiments and numerical simulations. Acoustic propagation models are developed and adapted for refractive index depending upon meteorological conditions. A high-resolution multi-nested environmental forecasting model forced by coarse global analysis is applied to predict real meteorological profiles at fine scales. These profiles are then used as input for the acoustic models. Numerical methods for producing higher resolution acoustic refractive index fields are proposed. These include spatial and temporal nested meteorological simulations with vertical grid refinement. It is shown that vertical nesting can improve the prediction of finer structures in near-ground temperature and velocity profiles, such as morning temperature inversions and low level jet-like features. Accurate representation of these features is shown to be important for modeling sound refraction phenomena and for enabling accurate noise assessment. Comparisons are made using the acoustic model for predictions with profiles derived from meteorological simulations and from field experiment observations in Phoenix, Arizona. The challenges faced in simulating accurate meteorological profiles at high resolution for sound propagation applications are highlighted and areas for possible improvement are discussed. A detailed evaluation of the environmental forecast is conducted by investigating the Surface Energy Balance (SEB) obtained from observations made with an eddy-covariance flux tower compared with SEB from simulations using several physical parameterizations of urban effects and planetary boundary layer schemes. Diurnal variation in SEB constituent fluxes are examined in relation to surface layer stability and modeled diagnostic variables. Improvement is found when adapting parameterizations for Phoenix with reduced errors in the SEB components. Finer model resolution (to 333 m) is seen to have insignificant ($<1\sigma$) influence on mean absolute percent difference of 30-minute diurnal mean SEB terms. A new method of representing inhomogeneous urban development density derived from observations of impervious surfaces with sub-grid scale resolution is then proposed for mesoscale applications. This method was implemented and evaluated within the environmental modeling framework. Finally, a new semi-implicit scheme based on Leapfrog and a fourth-order implicit time-filter is developed. / Dissertation/Thesis / Doctoral Dissertation Mechanical Engineering 2014

Orientador: Eliseu Savério Sposito / Banca: Marcos Kazuo Matushima / Banca: Paulo Fernando Cirino Mourão / Resumo: Os eixos de desenvolvimento referem-se às grandes vias de circulação de pessoas, mercadorias, bens, serviços e informações, balizados por uma rede de centros urbanos, e que estimulam a localização das atividades industriais. No Estado de São Paulo, os eixos de desenvolvimento podem ser visualizados ao longo de importantes rodovias que fazem a ligação da metrópole paulista com o interior e que funcionaram como canais para a desconcentração urbano-industrial que se iniciou na década de 1970 e se intensificou na década de 1980. O eixo da rodovia Washington Luiz (trecho Araraquara São José do Rio Preto), duplicado no início da década de 1990, somente nos últimos anos passa a atuar como um dos fatores de localização industrial para o município de Itápolis na atração de algumas indústrias desconcentradas de outras regiões. No entanto, a maioria das indústrias de Itápolis é de capital local (70,37% das indústrias pesquisadas). Os principais ramos industriais observados na pesquisa foram as agroindústrias e as confecções. São indústrias classificadas como tradicionais ou de trabalho intensivo e estão ligadas aos antigos fatores de localização industrial, como a proximidade das matériasprimas e a disponibilidade de mão-de-obra. A economia de Itápolis é baseada fundamentalmente na agropecuária. O município possui o maior PIB agrícola do Brasil e foi responsável por 0,6% de toda a produção agrícola brasileira em 2002. Em 2003, a participação de Itápolis no valor adicionado da agricultura estadual foi de 1,8%. A citricultura é responsável pela geração de 80% do ICMS. O dinamismo da agricultura constitui-se em um importante atrativo para a atividade industrial, seja...(Resumo completo, clicar no acesso eletrônico abaixo) / Abstract: Development axles refer to big circulation routes of people, goods, services and information marked out by a network of urban centers, which foster industrial activities location. In the State of São Paulo, these development axles can be seen along important freeways that connect the capital with the country and they worked as channels for urban-industrial concentration changes, which began in the 70's and became stronger in the 80's. The axle of Washington Luiz freeway (between the cities of Araraquara and São José do Rio Preto), which was doubled at the beginning of the 90's, has only contributed to attract some industries from other areas to the district of Itápolis in the last few years. However, most of the industries in the town were born with local investment (70.37% of the ones researched). The main industrial branches observed were agriculture-industry and clothes. They can be considered traditional or intensive work and are linked to old factors of industrial location, such as being close to raw materials and work force availability. Itápolis economy is essentially based in agriculture. The district has the highest agricultural GDP of Brazil, being responsible for 0.6% of the Brazilian agricultural production in 2002. In 2003, its participation in the state agriculture was 1.8%. The citrus culture is responsible for producing 80% of ICMS (Brazilian tax over goods and services movement). A dynamic agriculture fully attracts industrial activity in the...(Complete abstract, click eletronic address below) / Mestre

Master of Science

Recent years have seen a renewed interest in Variable Speed Limit (VSL) strategies. New opportunities for VSL as a freeway metering mechanism or a homogenization scheme to reduce speed differences and lane changing maneuvers are being explored. This paper examines both the macroscopic and microscopic effects of different speed limits on a traffic stream, especially when adopting low speed limits. To that end, data from a VSL experiment carried out on a freeway in Spain are used. Data include vehicle counts, speeds and occupancy per lane, as well as lane changing rates for three days, each with a different fixed speed limit (80 km/h, 60 km/h, and 40 km/h). Results reveal some of the mechanisms through which VSL affects traffic performance, specifically the flow and speed distribution across lanes, as well as the ensuing lane changing maneuvers. It is confirmed that the lower the speed limit, the higher the occupancy to achieve a given flow. This result has been observed even for relatively high flows and low speed limits. For instance, a stable flow of 1942 veh/h/lane has been measured with the 40 km/h speed limit in force. The corresponding occupancy was 33%, doubling the typical occupancy for this flow in the absence of speed limits. This means that VSL strategies aiming to restrict the mainline flow on a freeway by using low speed limits will need to be applied carefully, avoiding conditions as the ones presented here, where speed limits have a reduced ability to limit flows. On the other hand, VSL strategies trying to get the most from the increased vehicle storage capacity of freeways under low speed limits might be rather promising. Additionally, results show that lower speed limits increase the speed differences across lanes for moderate demands. This, in turn, also increases the lane changing rate. This means that VSL strategies aiming to homogenize traffic and reduce lane changing activity might not be successful when adopting such low speed limits. In contrast, lower speed limits widen the range of flows under uniform lane flow distributions, so that, even for moderate to low demands, the under-utilization of any lane is avoided. These findings are useful for the development of better traffic models that are able to emulate these effects. Moreover, they are crucial for the implementation and assessment of VSL strategies and other traffic control algorithms.

This abstract deals with the control of truck platoons traveling in freeways. In order to improve their travel performance, in terms of travelling times and comfort and to guarantee safety, a hierarchical control scheme is proposed for each platoon. At the high level, the reference speed is computed according to a PI-based control rule with the main aim of reducing the time spent by the platoon in the congested area. This reference speed is communicated to the low control level which implements a Linear Quadratic Tracking policy and determines the optimal speed for each truck in the platoon. The application of these hierarchical controllers to a case study shows the effectiveness of the proposed scheme.