A distância de visibilidade de parada deve ser garantida ao longo de toda a extensão de uma rodovia por questões de segurança. Elementos da seção transversal podem se tornar obstruções que interferem nas distâncias de visibilidade do projeto. Este é o caso do uso de barreiras ao invés de canteiros centrais em rodovias bidirecionais, especialmente ao longo de curvas à esquerda. Desta forma, este trabalho analisa o posicionamento de barreiras em cenários hipotéticos aclives planos e declives com uso de simulações gráficas tridimensionais. O afastamento lateral da barreira, em relação à pista de rolamento, foi definido em função de cada velocidade de projeto e de cada raio de curva horizontal analisados. Os diagramas gerados foram comparados com modelo de afastamento de objetos fixos em curvas horizontais, presente como recomendações em manuais nacionais. As diferenças encontradas indicam a viabilidade da metodologia utilizada, em que o projeto foi considerado como um todo, o qual se desenvolve tridimensionalmente. / Stopping Sight Distance must be guaranteed throughout of a highway for safety reasons. However, cross section elements can become obstructions which interfere on design sight distances. This occurs when barriers are used instead of medians on bidirectional highways, especially along left curves. Therefore, this paper analyzes the barriers placement on hypothetical scenarios upgrades, plans and downgrades using three-dimensional graphics simulations. The lateral offset of the barrier in relation to the roadway was defined according to each design speed and each radius of the horizontal curve analysis. For each scenario were generated diagrams, which use compared with offset model of fixed objects on horizontal curves presents as recommendation in national manuals. The differences indicate the viability of the methodology used, where the project was considered as a whole, which develops three-dimensionally.

Die kürzer gewordenen Bremswege moderner Pkw erlauben ein schnelleres Anhalten im Gefahrenfall. Dadurch erscheint es möglich, zukünftig auch kürzere Haltesichtweiten im Straßenentwurf zu fordern. Es ist jedoch fraglich, ob ein verringertes Sichtweitenniveau eine ausreichende Fahrerorientierung gewährleisten kann. In drei umfangreichen Versuchsreihen wurde das Blick- und Fahrverhalten von Probanden bei Versuchsfahrten im realen Verkehr sowie im Fahrsimulator untersucht. Das Untersuchungsprogramm umfasste Fahrten mit Blickbewegungsmessung, die Bearbeitung von Nebenaufgaben sowie die Reaktion an plötzlich auftauchenden Hindernissen. Ausgewertet wurden der Verlauf von Beanspruchungsindikatoren, Zuwendungshäufigkeiten zu Nebenaufgaben sowie Parameter des Fahrverhaltens bei geringer werdenden Sichtweiten. Aus den Ergebnissen konnten verallgemeinerungsfähige Aussagen zum Verhalten von Fahrern bei unterschiedlichen Sichtweiten abgeleitet werden. Es wurden Sichtweitenbereiche definiert, in denen eine ansteigende Beanspruchung der Fahrer auf eine unzureichende Orientierung über den Streckenverlauf hinweist bzw. in denen plötzlich auftauchende Hindernisse nur noch unter Schwierigkeiten gemeistert werden können. Daraus wurde ein entwurfsklassenbezogenes Modell einer Orientierungssichtweite abgeleitet, das die Belange der Fahrerorientierung im Straßenentwurf würdigt. Die Ergebnisse wurden bei der Fortschreibung der Entwurfsrichtlinien für Straßen berücksichtigt.

A distância de visibilidade de parada deve ser garantida ao longo de toda a extensão de uma rodovia por questões de segurança. Elementos da seção transversal podem se tornar obstruções que interferem nas distâncias de visibilidade do projeto. Este é o caso do uso de barreiras ao invés de canteiros centrais em rodovias bidirecionais, especialmente ao longo de curvas à esquerda. Desta forma, este trabalho analisa o posicionamento de barreiras em cenários hipotéticos aclives planos e declives com uso de simulações gráficas tridimensionais. O afastamento lateral da barreira, em relação à pista de rolamento, foi definido em função de cada velocidade de projeto e de cada raio de curva horizontal analisados. Os diagramas gerados foram comparados com modelo de afastamento de objetos fixos em curvas horizontais, presente como recomendações em manuais nacionais. As diferenças encontradas indicam a viabilidade da metodologia utilizada, em que o projeto foi considerado como um todo, o qual se desenvolve tridimensionalmente. / Stopping Sight Distance must be guaranteed throughout of a highway for safety reasons. However, cross section elements can become obstructions which interfere on design sight distances. This occurs when barriers are used instead of medians on bidirectional highways, especially along left curves. Therefore, this paper analyzes the barriers placement on hypothetical scenarios upgrades, plans and downgrades using three-dimensional graphics simulations. The lateral offset of the barrier in relation to the roadway was defined according to each design speed and each radius of the horizontal curve analysis. For each scenario were generated diagrams, which use compared with offset model of fixed objects on horizontal curves presents as recommendation in national manuals. The differences indicate the viability of the methodology used, where the project was considered as a whole, which develops three-dimensionally.

Die kürzer gewordenen Bremswege moderner Pkw erlauben ein schnelleres Anhalten im Gefahrenfall. Dadurch erscheint es möglich, zukünftig auch kürzere Haltesichtweiten im Straßenentwurf zu fordern. Es ist jedoch fraglich, ob ein verringertes Sichtweitenniveau eine ausreichende Fahrerorientierung gewährleisten kann. In drei umfangreichen Versuchsreihen wurde das Blick- und Fahrverhalten von Probanden bei Versuchsfahrten im realen Verkehr sowie im Fahrsimulator untersucht. Das Untersuchungsprogramm umfasste Fahrten mit Blickbewegungsmessung, die Bearbeitung von Nebenaufgaben sowie die Reaktion an plötzlich auftauchenden Hindernissen. Ausgewertet wurden der Verlauf von Beanspruchungsindikatoren, Zuwendungshäufigkeiten zu Nebenaufgaben sowie Parameter des Fahrverhaltens bei geringer werdenden Sichtweiten. Aus den Ergebnissen konnten verallgemeinerungsfähige Aussagen zum Verhalten von Fahrern bei unterschiedlichen Sichtweiten abgeleitet werden. Es wurden Sichtweitenbereiche definiert, in denen eine ansteigende Beanspruchung der Fahrer auf eine unzureichende Orientierung über den Streckenverlauf hinweist bzw. in denen plötzlich auftauchende Hindernisse nur noch unter Schwierigkeiten gemeistert werden können. Daraus wurde ein entwurfsklassenbezogenes Modell einer Orientierungssichtweite abgeleitet, das die Belange der Fahrerorientierung im Straßenentwurf würdigt. Die Ergebnisse wurden bei der Fortschreibung der Entwurfsrichtlinien für Straßen berücksichtigt.

The majority of the road infrastructure in developing countries consists oftwo-lane highways with one lane in each travel direction. Operational efficiency of these highways is derived fromintermittent passing zones where fast vehicles are permitted by design to pass slow vehicles using the opposite traffic lane. Passing zonescontributeto reduction oftravel delay and queuing of fast vehiclesbehind slow vehicles. Thishoweverincreases crash risks between passing and opposite vehiclesespecially at high traffic volumesdue to reduction of passing opportunities.Reduction of passing-related crash risks is therefore a primary concern ofpolicy makers, planners, and highway design engineers. Despite the wide application of passing zones on two-lane highways, there is limited knowledge on the underlying causal mechanisms that exacerbate crash risks, and the essential tools to assess safety of the passing zones. This thesis presentsa methodology to appraisesafety of two-lane rural highways based on observed operation of passing zones.Theproposed methodology takes into accountthe impact of traffic and geometric factors onthe rate passing maneuvers end insidepassing zonesand in the no-passing zones, adequacy ofthe designpassing sight distance,and time-to-collision at the end of passing maneuvers.Thethesis is comprised offive papers addressing capacity and safety aspectsof passing zoneson two-lane rural highways. Paper Ipresents a review of the literature on capacity and safety of passing zones. Paper IIdiscusses adequacy of the design passing sight distance based on the sight distance required to complete a passing maneuverusing observed data. Paper IIIdiscusses formulation, estimation, and application of a model to predict the passing rate using geometric and traffic factors, and applications. Paper IVdiscusses risk appraisal of the passing process based on the probability to complete passing maneuvers with time-to-collision less than 3.0 seconds taking into account the accepted gap in the opposite direction and the passing duration. Paper Vdiscusses formulation and estimation of models to predict the probability and the rate at which passing maneuvers end in a no-passing zone, and applications. Resultsshow that passing zones of lengths between 1.30and 2.50km aregood for both operational efficiency and safety.Passing zones of lengths between 0.50and 1.30km exhibitincreasing crash risks resulting from delayed passing maneuvers thatend in the no-passing zone where the sight distance is limited to evadepotential collisions. Safety of these passing zones could be enhanced with additional signage to indicate the farthestpoint along a passing zone that maneuvers can be initiated so as not to end in a no-passing zone. Passing zones less than 0.50km compel drivers to commence passing maneuvers close to the beginning of the passing zone,and should be avoided during design for safety reasons. The results further show that the passing rate depends on the length of the passing zone, absolute vertical grade, traffic volume in two travel directions, directional split, 85thpercentile speed of free flow vehicles,and percent of heavy vehicles in the subject direction. The peak-passing rate also known as the passing capacity occurs at 200, 220, and 240vph in the subject direction for 50/50, 55/45, and 60/40directional splits, respectively. The rate at which passing maneuvers end in a no-passing zone increaseswith traffic volume and unequal distribution of traffic in two directions, absolute vertical grade, and percent of heavy vehiclesin the subject direction. The thesis furtherdiscusses practical applications of the study findings in highway planning and design to enhancesafety and improve operational efficiency of two-lane rural highways. / <p>QC 20151106</p>

Crashes categorized as running red light or left turning are most likely to occur at signalized intersections and resulted in substantial severe injuries and property damages. This dissertation mainly focused on these two types of vehicle crashes and the research methodology involved several perspectives. To examine the overall characteristics of red-light running and left-turning crashes, firstly, this study applied 1999-2001 Florida traffic crash data to investigate the accident propensity of three aspects of risk factors related to traffic environments, driver characteristics, and vehicle types. A quasi-induced exposure concept and statistical techniques including classification tree model and multiple logistic regression were used to perform this analysis. Secondly, the UCF driving simulator was applied to test the effect of a proposed new pavement marking countermeasure which purpose is to reduce the red-light running rate at signalized intersections. The simulation experiment results showed that the total red-light running rate with marking is significantly lower than that without marking. Moreover, deceleration rate of stopping drivers with marking for the higher speed limit are significantly less than those without marking. These findings are encouraging and suggesting that the pavement marking may result in safety enhancement as far as right-angle and rear-end traffic crashes at signalized intersections. Thirdly, geometric models to compute sight distances of unprotected left-turns were developed for different signalized intersection configurations including a straight approach leading to a straight one, a straight approach leading to a curved one, and a curved approach leading to a curved one. The models and related analyses can be used to layout intersection design or evaluate the sight distance problem of an existing intersection configuration to ensure safe left-turn maneuvers by drivers.

Current design methods in transportation engineering do not simultaneously address the levels of risk and service associated with the design and use of various highway geometric elements. Passing sight distance (PSD) is an example of a geometric element designed with no risk measures. PSD is provided to ensure the safety of passing maneuvers on two-lane roads. Many variables decide the minimum length required for a safe passing maneuver. These are random variables and represent a wide range of human and vehicle characteristics. Also, current PSD design practices replace these random variables by single-value means in the calculation process, disregarding their inherent variations. The research focuses on three main objectives. The first goal is to derive a PSD distribution that accounts for the variations in the contributing parameters. Two models are devised for this purpose, a Monte-Carlo simulation model and a closed form analytical estimation model. The results of both models verify each other and differ by less than 5 percent. Using the PSD distribution, the reliability index of the current PSD criteria are assessed. The second goal is to attach risk indices to the various PSD lengths of the obtained distribution. A unique microscopic simulation is devised to replicate passing maneuvers on two-lane roads. Using the simulation results, the author is able to assess the risk of various PSD lengths for a specific design speed. The risk index of the AASHTO Green Book and the MUTCD PSD standards are also obtained using simulation. With risk measures attached to the PSD lengths, a trade-off analysis between the level of service and risk is feasible to accomplish. The last task is concerned with applying the Highway Capacity Manual concepts to assessing the service measures of the different PSD lengths. The results of the final trade-off analysis show that for a design speed of 50 mph, the AASHTO Green Book and the MUTCD standards overestimate the PSD requirements. The criteria can be reduced to 725 ft and still be within an acceptable risk level. / Ph. D.

This study introduces a multi-objective optimization framework for the re-dimensioning of the cross-section elements of rural horizontal curves with limited sight distance. The optimization aims at minimizing both the risk of collision associated with the limited sight distance and the expected collision frequency corresponding to the cross-section elements’ dimensions. The risk component was assessed using an index known as (Pnc), which is developed based on the reliability theory. The change in collision frequency corresponding to the change of the cross-section elements was extracted from the literature. The risk and the safety components were then combined into one measure (CMFcombined) to develop a direct measure of the safety impacts of the optimization. The proposed framework was applied to five restricted curves in British Columbia, Canada, considering various scenarios. The results showed a considerable reduction in the Pnc value (ranging from 12% to 73%) and the expected collision frequency (ranging from 10% to 31%) after optimization. The estimated combined reduction in collision frequency (CMFcombined) was estimated to vary between 48% and 76%. The results showed that the optimization of cross-section elements can improve the safety of horizontal curves significantly. The framework presented in this study would support transportation engineers in selecting optimal dimensions of cross-section elements of restricted horizontal curves, understanding the safety consequences of selecting a specific cross-section configuration, and assessing the economic viability of different design options. / Thesis / Master of Applied Science (MASc)

Overtaking maneuver is very complex event influenced by many parameters. The most important parameters are vehicle performance, longitudinal slope, the speed at the beginning of the maneuver, the reaction time of the driver. Overtaking distance at CSN 73 6101 is determined on the basis of a simplified physical model. It considers constant speed of vehicles (overtaking and overtaken) and it does not consider a longitudinal gradient of road. This calculation is used for several decades and it is required to verify this procedure. That was the purpose of this work. Detailed physical model was performed for several types of passenger vehicles, performance curves and gear changes were included too. Distances between vehicles at the beginning and in the end of the maneuver were chosen with regard to reaction times of drivers. Distances were compared with conclusions of observation studies. Input values of some parameters were determined by own measurement and compared with data reported in the literature. The analysis was performed using the video camera positioned at the front and rear of the vehicle. For selected vehicle were conducted simulations testing the influence of particular parameters. The parameters with the biggest influence were longitudal slope of the road and rolling friction. To achieve results useful for a possible regulations update for the design of roads another simulation models for 43 variants of passenger cars with different engines and transmissions were done. The vehicles were divided into categories based on engine capacity and engine power (up to 1400 ccm, over 1400 ccm; 66 kW to over 66 kW). Results were compiled in tabular form that could be used to discuss modifications to CSN 73 6101 Design of roads.