<p> Wider bike facilities intuitively accommodate a greater number of cyclists in the same amount of time, but specific queue discharge characteristics associated with varying widths and/or types of bike facilities have not been thoroughly documented. </p><p> The focus of this research analyzed queues of cyclists at four signalized intersections in Portland, OR with varying widths on the approach and downstream intersection legs. A total of 2,820 cyclists within 630 groups of queued cyclists were observed at five different intersection layouts in Portland, Oregon. The layouts consisted of: a standard bike lane six feet wide connecting bicyclists to a standard bike lane six feet wide, a standard bike lane five feet wide connecting bicyclists to two standard bike lanes each five feet wide, a buffered bike lane 12 feet wide connecting bicyclists to a standard bike lane 6.5 feet wide, a bike box 21 feet wide connecting bicyclists to a buffered bike lane 10 feet wide, and a bike box 15 feet wide connecting bicyclists to two standard bike lanes each five feet wide. </p><p> For each configuration, the following aspects were analyzed: average headway per cyclist within each queue, the time required for queues to enter the intersection, the time required for queues to clear the intersection, the number of cyclists within queues, the width of the bicycle facilities, the approach grade, and the utilization of a bike box at the intersection approach if it was present. </p><p> The first major focus of the analysis reviewed the average headway values associated with each observed queue of cyclists. The queue size with the lowest mean of the average headway was for groups of seven cyclists with an average headway of approximately 0.8 seconds per cyclist. For queues larger than seven in size, the mean of the average headway remained relatively stable until queues of 12 in size and started to slightly increase toward approximately 1.0 seconds for queues larger than 12 cyclists. In addition, it appears that utilization of a bike box has a potential relationship with a reduced average headway as compared to queues that do not utilize a bike box. The associated reduction in the mean of the average headway was approximately 0.2 to 0.3 seconds per cyclist for queues of three or more in size. </p><p> The second major focus of the analysis reviewed the queue discharge rate associated with each observed queue of cyclists. The results appear to potentially indicate that wider bike facilities approaching an intersection, wider receiving bike facilities, or utilization of a bike box generally discharge queues of bicyclists into the intersection over a shorter amount of time as compared to facilities that are narrower or underutilized. The installation of a bike box at one of the study intersections increased the approach width from five to 15 feet and resulted in consistently lower average discharge times for all queue sizes, a reduction of greater than one second for queues of two cyclists to as much as about four seconds for queues of nine cyclists. </p><p> The third major focus of the analysis reviewed the intersection clearance time associated with each observed queue of cyclists. The results appear to potentially indicate that wider bike facilities approaching an intersection, wider receiving bike facilities, or utilization of a bike box generally clear queues of bicyclists through the intersection over a shorter amount of time as compared to facilities that are narrower or underutilized.</p><p>

<p> The future success of traffic management is contingent upon the advancement of information logistic systems. The ability to provide accurate, valid, and timely information is critical to the effectiveness of an intelligent transportation system&rsquo;s ability to improve public safety and economic growth. Traffic Operation Centers (TOC) receive and disseminate information with various actors in real-time and near real-time environments. Using the traffic incident management business process for a Traffic Operation Center, this research explores the effects of designing a traffic management system in context to the business process. Two system designs for a TOC are compared using the system architecture maps and incident duration time stamps captured during the use of each system. The results show the impact of using process-oriented information logistics (POIL) during the design phase when developing traffic management systems. </p><p>

<p> Louisiana currently has 30 roundabouts in operation and hundreds of roundabouts in the planning and design stage. The Louisiana Department of Transportation and Development (DOTD) is very interested in knowing the safety performance of existing roundabouts in the state. </p><p> As revealed in this paper, the safety effectiveness of a roundabout depends on its prior traffic control type, conformity to the geometric design guidelines, changes in layout of intersection, and nighttime lighting conditions. All 19 roundabouts investigated by this study demonstrated significant reduction in injury crashes because of lower operating speed, reduced right-angle collisions, and elimination of head-on and left turn crashes. Based on changes in the number of conflicting points and traffic control method, it is understandable why the most significant and consistent safety improvement was associated with the roundabouts previously controlled by stop signs on minor streets. The Crash Modification Factor (CMF), as estimated by the Empirical Bayes (EB) method, for this group of roundabouts is 0.28 with a standard deviation of 0.054. The roundabout is economically justified for its safety benefit alone based on the benefit-cost ratio analysis for this group of roundabouts. </p><p> The study did identify a few compounding factors at the individual intersections, such as questionable geometric design elements, increased number of conflicting points, unpredictable human behavior, and lack of lighting at night.</p><p>

<p> Evident similarities and links between the outcomes of traffic crashes and stranded (or constrained) mobility have been identified and are reported in this research. Generally, a high level of travel activities is an indicator of high crash exposure. However, studies have shown that the highest rates of traffic fatalities occur in low- and middle-income regions, where many citizens experience relatively low levels of motorized travel. This ironic observation reveals serious challenges facing transport mobility systems in the less privileged regions of the world. Studies on traffic crashes and mobility constraints also reveal that they both have individual and regional variations in their occurrence, effects, and severities. Consequently, the outcomes of traffic crashes and constrained mobility are serious public health concerns worldwide.</p><p> As public health problems, their study is analogous to the study of diseases and other injuries and thus, suitable for the application of epidemiological techniques. This dissertation therefore explores the use of epidemiological techniques to analyze traffic crashes and mobility/accessibility constraints from a human-centered perspective. The dissertation therefore consists of two major focus areas. The first part of the study applies widely used epidemiology/public health &ndash; based statistical tools to analyze traffic crashes with the aim of gaining better understanding of the human-centered causes and factors that influence these causes, and how these ultimately affect the severity of crashes. This part is further divided into two sub-sections. The first sub-section used latent class analysis to identify homogeneous clusters of human-centered crash causal factors and then applied latent class logit and random parameters logit modeling techniques to investigate the effects of these factors on crash outcomes. The second sub-section of the first part of the dissertation applies multilevel regression analysis to understand the effects of driver residential factors on driver behaviors in an attempt to explain the area-based differences in the severity of road crashes across sub-regions. Both studies are necessary to develop potential human-centered mitigations and interventions and for the effective and targeted implementation of those countermeasures. The second part of the study provides an epidemiological framework for addressing mobility/accessibility constraints with a view to diagnosing symptoms, recommending treatment, and even discussing the idea of transmission of constrained mobility among city dwellers. The medical condition, hypomobility, has been used to connote constrained mobility and accessibility for people in urban areas. In transportation and urban studies, hypomobility can result in a diminished ability to engage in economic opportunities and social activities, hence deepening poverty and social exclusion and increasing transport costs, among other negative outcomes. The condition is especially pronounced in poor urban areas in developing countries. The framework proposed in this study is expected to help identify and address barriers to mobility and accessibility in the rapidly growing cities throughout the developing world, with particular applicability to the rapidly developing cities in Sub-Saharan Africa. </p><p> Ultimately, this dissertation explores the application of epidemiological techniques to two major transportation problems: traffic safety and constrained mobility. The techniques presented in this dissertation provide policy makers, agencies, and transport professionals with tools for evidence-based policies and effective implementation of appropriate countermeasures.</p><p>

<p>In this research study, high plastic and medium plastic soils were used in evaluating the physical and mechanical properties of fly ash-soil Geopolymer mixtures. Sieve analysis and Atterberg limit tests were conducted to classify the soil. Class F fly ash, an industrial byproduct, was used in the alkaline environment of a mixture of sodium silicate and various concentration of sodium hydroxide to prepare fly ash based Soil-Geopolymer mixtures. The modified proctor test was conducted to investigate the moisture-density characteristics of mixtures. Based on literature search and preliminary experiments, the experimental design matrix of was developed by using various combination of fly ash content, alkaline ratio, and concentration of sodium hydroxide. Several mixtures based on the experimental design matrix were compacted, cured at elevated temperature and tested for unconfined compressive strength. Regression analysis was conducted to develop regression models to optimize and conduct sensitivity of the compressive strength in relation to mix variables of Soil-Geopolymer mixtures. Based on sensitivity analysis and UCS criteria recommended by DOTD Louisiana, two mixtures were selected for further evaluation along with Standard soil-cement mixtures. The resilience modulus, dynamic modulus, and durability test were conducted for selected Soil-Geopolymer mixtures and standard soil-cement mixtures, as recommended by LA DOTD. The result of the study showed that the alkali activated soil-fly ash mixtures fulfilled the compressive strength criteria of cement treated design (CTD) and cement stabilize design (CSD) of 150 psi and 300 psi, as recommended by LA DOTD. Also, the results indicated that Soil-Geopolymer showed satisfactory performance under compressive strength test and dynamic loading tests. Further, the Soil-Geopolymer mixtures passed wet and dry durability test criteria. Based on mechanical and durability characteristics evaluated it can be recommended that Soil-Geopolymer mixtures studied in this study has an immense potential to be used as pavement subgrade, subbase, and bases.

<p>There can be environmental problems associated with using cement to stabilize soils. Thus, a substitute for cement in the stabilization of road base/subbase is desirable. A Geopolymer can be a good alternative for cement stabilization, as geopolymer produces fewer greenhouse gasses compared to cement. Soil-RAP-Geopolymer as road base and subbase material have been investigated in this research. The standard method of soil stabilization in Louisiana is soil-cement, hence 5% and 10% soil-cement was selected for the comparison. In addition to the physical and mechanical tests, the durability test was also conducted to evaluate the long-term performance of Soil-RAP-Geopolymer mixtures developed in this study. Two different types of soils with medium and high plasticity indices from Louisiana were used. Water content was substituted with alkali at an OMC level to compact the Soil-RAP-Geopolymer at a maximum dry density. An experimental design matrix was established for developing statistical based regression models for the UCS and to optimize the mixture design. Higher FA and RAP content produced mixtures with higher strength, and hence 25% FA and 25% RAP provided the better performance in terms of mechanical properties. Optimum sodium silicate content however depended on the type of soil, and the percentage of FA and RAP in the mixture. UCS, resilient modulus, dynamic modulus and elastic modulus of the optimum mixture were found to be better than 5% and 10% of soil-cement mixtures. The optimum Soil-RAP-Geopolymer mixtures successfully passed the minimum strength criteria of CSD and CTD as used by Louisiana Department of Transportation and Development (DOTD). The durability characteristics also confirmed that the developed Soil-RAP-Geopolymer mixture could be used in the field of soil stabilization. The microstructure and morphology analysis on optimum mixtures confirmed that geopolymer was formed with FA, RAP, and soil in the presence of alkali.

About twenty percent of the U.S. National Highway System is under construction during the peak summer roadwork season. Fifty percent of all highway congestion is attributed to nonrecurring conditions and work zones are estimated to account for nearly twenty four percent of nonrecurring delay. Work zones account for two percent of roadway crashes and more than 1,000 fatalities per year. The major question on which this research focuses is: "How do work zone delineation strategies, intelligent transportation systems (ITS) technologies, and driver behavior impact traffic flow and crash potential in and around work zones?" To address this question effectively, one might consider assessing actual traffic situations under local conditions with the aid of a microscopic simulation model. Such simulation tools could be useful to individuals designing work zone deployment plans, developing work zone traffic management concepts, deciding on the use of ITS applications in work zones, and formulating alternate route strategies. In addition, such tools may improve the ability to visualize the impact of delineation and dynamic merge guidance strategies as well as to quantitatively assess the impact on delay and the occurrence of high crash potential situations in and around work zone areas. The underlying objective of this research is to improve the way researchers and practitioners are able to explain and predict traffic conditions and driver behavior as they are impacted by work zone strategies including variable message signs, static signage, tapers, arrow boards, and positive separation. Central to this research was the formulation of an algorithm that improves upon traditional car following theory by incorporating factors such as driver familiarity, adaptability, aggression, and accommodation to the changing road conditions found in work zones. The use of these concepts incorporates two notions: (1) drivers must manage interaction with both the roadway and other drivers; and (2) drivers exhibit varying preferences for early or late merges based on their willingness to respond to upcoming lane restrictions and their inclination to be passive or aggressive in forced merge situations.

Congestion is a world-wide problem in transportation. One major reason is random interruptions. The traffic network is inherently stochastic, and strong dependencies exist among traffic quantities, e.g., travel time, traffic speed, link volume. Information in stochastic networks can help with adaptive routing in terms of minimizing expected travel time or disutility. Routing in such networks is different from that in deterministic networks or when stochastic dependencies are not taken into account. This dissertation addresses the optimal routing problems, including the optimal a priori path problem and the optimal adaptive routing problem with different information scenarios, in stochastic and time-dependent networks with explicit consideration of the correlations between link travel time random variables. There are a number of studies in the literature addressing the optimal routing problems, but most of them ignore the correlations between link travel times. The consideration of the correlations makes the problem studied in this dissertation difficult, both conceptually and computationally. The optimal path finding problem in such networks is different from that in stochastic and time-dependent networks with no consideration of the correlations. This dissertation firstly provides an empirical study of the correlations between random link travel times and also verifies the importance of the consideration of the spatial and temporal correlations in estimating trip travel time and its reliability. It then shows that Bellman's principle of optimality or non-dominance is not valid due to the time-dependency and the correlations. A new property termed purity is introduced and an exact label-correcting algorithm is designed to solve the problem. With the fast advance of telecommunication technologies, real-time traffic information will soon become an integral part of travelers' route choice decision making. The study of optimal adaptive routing problems is thus timely and of great value. This dissertation studies the problems with a wide variety of information scenarios, including delayed global information, real-time local information, pre-trip global information, no online information, and trajectory information. It is shown that, for the first four partial information scenarios, Bellman's principle of optimality does not hold. A heuristic algorithm is developed and employed based on a set of necessary conditions for optimality. The same algorithm is showed to be exact for the perfect online information scenario. For optimal adaptive routing problem with trajectory information, this dissertation proves that, if the routing policy is defined in a similar way to other four information scenarios, i.e., the trajectory information is included in the state variable, Bellman's principle of optimality is valid. However, this definition results in a prohibitively large number of the states and the computation can hardly be carried out. The dissertation provides a recursive definition for the trajectory-adaptive routing policy, for which the information is not included in the state variable. In this way, the number of states is small, but Bellman's principle of optimality or non-dominance is invalid for a similar reason as in the optimal path problem. Again purity is introduced to the trajectory-adaptive routing policy and an exact algorithm is designed based on the concept of decreasing order of time.

Many claim that, with regard to transportation infrastructure, only partnerships between public and private entities, which draw on the strengths of both, can achieve the goals of enhancing operational efficiency, increasing service delivery, improving asset maintenance, and stretching scarce federal, state, and local tax dollars. While some completed public-private partnership (P3) agreements on existing toll roads in the United States have seen a measure of success, others have raised critical questions pertaining to the true costs and benefits associated with these agreements for all stakeholders. Of particular concern is an apparent reliance on monetary calculations alone to determine toll road lump sum value. This primary focus on monetary considerations appears to neglect a number of non-monetary variables associated with potential costs and benefits. Four distinct groups of variables to consider in the decision process are presented in the dissertation: Monetary, Monetizable, Quantitative, and Qualitative. The last two groups represent variables of a non-monetary nature, which can reflect the much larger stewardship role that government plays in our society. The objectives of this research are twofold: to formulate a conceptual framework for a decision support system (DSS); and to propose an approach, including a set of analytical methods, that assesses the costs, benefits and other impacts associated with alternative P3 strategies. The primary user of the conceptual framework is identified as the public sector decision maker who has been asked to make recommendations regarding different strategies of toll road operation. Two analytical methods are presented. The first uses cash flow diagrams to calculate the net present value (NPV) for each of three core P3 strategies. The second, weighs the relative importance of quantitative and qualitative (non-monetizable) variables. When used as part of a seven-step process, these two analytical methods help create a decision support system framework that provides stakeholders with a more complete analysis of the costs and benefits associated with the P3 toll road decision process.

The forces which led to widespread suburbanization resulted in the migration of job opportunities, especially in retailing and in industry. This migration in part led to public transit service decline since a substantial share of transit trips in urban areas consisted of work trips, particularly to the CBD. Most planning agencies in small and medium urban areas include transportation improvements as an integral part of their efforts to stimulate economic development in the central city. The extent to which transportation improvements impact the central city in such areas is an important issue for urban planners, transportation engineers, and other professionals involved in attempts to enhance the local economy. While it is extremely difficult to attribute changes in demographic and economic activity to specific transportation improvements, it is posited in this research that general conclusions regarding such changes can be drawn and related to transportation improvements if consistent patterns of changes can be observed in demographic and economic activities among a large number of cities. The objective of this research is twofold: (1) to examine the relationship between transportation, central city and CBD development, and (2) to develop an econometric model that will depict such relationships. This research depicts selected relationships between employment, population, economic activity and transportation using a system of equations in a recursive model. The models are based on a sample of 112 small and medium sized cities with a 1980 population between 50,000 to 500,000, located in 36 different states. The models were tested using data from 11 cities with a 1980 population of 500,000 to 1,000,000 from 10 different states. The consistent results suggest that growth in the basic manufacturing sector is an important factor for central city growth. Increases in manufacturing employment attract more people to the cities, which in turn changes the retail sector. Also transit service improvements help to improve the downtown economy, since a relatively large share of peak trips are by transit and most of these transit trips are work trips, particularly to the CBD. Increased work trips to the CBD will have a positive (although small) impact on CBD sales. (Abstract shortened with permission of author.)