Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
Browse
5 results
Search Results
Item Dynamic Traffic Management of Highway Networks(2022) Alimardani, Fatemeh; Baras, John S; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Efficient operation of traffic networks via management strategies can guarantee overall societal benefits for both the humans and the environment. As the number of vehicles and the need for transportation grows, dynamic traffic management aims to increase the safety and efficiency of the traffic networks without the need to change the infrastructure of the existing roads. Since the highway networks are considered permanent investments that are expensive to build and maintain, the main scope of this dissertation is to propose traffic flow models and methods to improve the efficiency of the current highway systems without the need to change their infrastructure. When all vehicles in a network are \textit{Human-Driven Vehicles} (HDVs), and changing the infrastructure is either so expensive or impossible, then one reasonable approach to improve the efficiency of traffic networks is through the control of traffic signal lights specially because the behavior of the human drivers cannot be directly controlled. A literature review of highway traffic control demonstrate that \textit{Ramp Metering} (RM) is one of the most commonly used approaches as it improves the network performance in regards to travel time, travel distance, throughput, etc and cost-wise, it is a very economical approach. As such, in this research, the ultimate goal focus is to extend the current literature on traffic managements of highway networks by offering new models and algorithms to improve this field. To reach this goal, the first step is to focus on improving and extending the current traffic flow models. There are two categories of traffic flow models in the literature: First-order models, and Second-order models. Many different extensions of the famous first-order model called the Cell-Transmission Model (CTM) have been proposed throughout the past decades, each one proposed based on different criteria and the specific needs of different applications. In the first part of this dissertation, a performance assessment of the most important extensions of CTM will be performed. Then, based on this evaluation, an extended version of the CTM, called the Piece-Wise Affine Approximation-CTM (\textit{PWA-CTM}), will be offered which will be proven to have better performance regarding the evolution of traffic flow and computation time comparing to the previous versions of this model. In the next step, the focus will be shifted to second-order models as they have better capabilities of modeling the behavior of traffic flow comparing to the first-order models. However, any optimization scheme for highway traffic control based on these models is highly nonlinear and computationally intensive. As such, in this part of the research, a linearization of the famous second-order model called the \textit{METANET} will be offered which is based on PWA approximations and also synthetic data generation techniques. With extensive simulations, it will be shown that this linearized approximation can greatly impact the computational complexity of any optimization-based traffic control framework based on this second-order traffic flow model. Moreover, to have significant traffic management improvements, not only the underlying traffic models, but also the control strategies should be enhanced. The availability of increasing computational power and sensing and communication capabilities, as well as advances in the field of machine learning, has developed \textit{learning-based} control approaches which can address constraint satisfaction and closed-loop performance optimization. In this chapter, \textit{Reinforcement Learning} (RL) algorithms will be investigated to solve the optimal control problem of RM. In the case of RM, RL-based techniques offer a potentially appealing alternative method to solve the problem at hand, since they are data-based and make no assumptions on the underlying model parameters. Towards this direction, it is convenient to study the road model as a multi-agent system of non-homogeneous networked agents. In the following, a novel formulation of the RM problem as an optimal control problem based on a first-order multi-agent dynamical system will be offered. Then, applying policy gradient RL algorithms, a probabilistic policy will be found that solves the ramp-metering problem. The performance of the optimal policy learnt will be investigated under different scenarios to evaluate its efficiency.Item Up Ahead(2020) Head, Bryan; Collier, Michael; Creative Writing; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Up Ahead documents the ways movement and speed inform, permit, and distort a speaker’s perception of narratives assumed both individually and collectively. The collection’s skeletal metaphor—the American interstate as vehicle for American opportunism and exceptionalism—dramatizes the tension (or lack thereof) in reckoning with the contradictions and fictions inherent in being a traveler, a husband, and an American. Many of the poems in Up Ahead pull real documents surrounding the planning, lobbying, and building of the interstate system (the largest human construction wonder in history) to parallel language found in the domestication of violence, and the absolution of individual guilt.Item EMPIRICAL ANALYSIS OF THE QUALITY, EFFECTIVNESS, AND LOCALIZED IMPACTS OF HIGHWAY DYNAMIC MESSAGE SIGN MESSAGES(2011) Fish, Robin Lee Wilson; Haghani, Ali; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The need to convey accurate, real-time travel information to road users has long been recognized by transportation engineers. One of the primary means to accomplish this is the operation of highway Dynamic Message Signs (DMS). Though utilized for over 50 years, the quality of messages used, their effectiveness in influencing traffic, and the localized impacts they have are not well documented. This thesis introduces Bluetooth traffic detection sensors as a new tool for evaluation of DMS message quality and resulting route choice decisions. In addition, highway speed sensors are used to determine whether DMS influence changes in local traffic speeds. The findings indicate DMS messages are generally accurate in communicating prevailing conditions and can influence the route choice behavior of drivers. The speed analysis indicated that certain messages have more influence on traffic than others, though the majority of messages do not negatively affect traffic speeds.Item STABILIZATION OF RECYCLED BASE MATERIALS WITH HIGH CARBON FLY ASH(2009) Cetin, Bora; Aydilek, Ahmet H.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)ABSTRACT Fly ashes produced by several power plants in United States occasionally contain significant amounts of unburned carbon due to common use of low nitrogen-oxide and sulphur-oxide burners in recent years. This ash cannot be reused in concrete production due to its reactivity with air entrainment admixtures and is being landfilled at large percentages. A study was conducted to stabilize low stiffness road surface material with high carbon fly ash. The non-cementitious Maryland fly ash was activated with another recycled material, lime kiln dust (LKD). California bearing ratio (CBR) and resilient modulus tests were conducted to determine the strength and stiffness, respectively, of the stabilized materials. Addition of LKD and curing of specimens generally increased CBR and summary resilient modulus (SMR) and lowered plastic strains, CBR increased with increasing CaO content as well as with CaO/SiO2 and CaO/(SiO2 + Al2O3) ratio of the mixtures; however, these parameters could not be correlated with the SMR. The unpaved road materials stabilized with LKD and fly ash is expected to lose 31 to 67% of their initial moduli after twelve cycles of freezing and thawing. Most of the factor considered on the thickness of the base layer and cost calculations.Item FIELD EVALUATION OF HYDROLOGIC AND WATER QUALITY BENEFITS OF GRASS SWALES WITH CHECK DAMS FOR MANAGING HIGHWAY RUNOFF(2009) Jamil, Nor Eliea Eluziea; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)ABSTRACT Title of Thesis: FIELD EVALUATION OF HYDROLOGIC AND WATER QUALITY BENEFITS OF GRASS SWALES WITH CHECK DAMS FOR MANAGING HIGHWAY RUNOFF Nor Eliea Eluziea Jamil, Master of Science, 2009 Thesis Directed By: Professor Allen P. Davis Departrment of Civil and Environmental Engineering Managing highway runoff is a complex storm water management problem. This research is an input/output field study that specifically examines the hydrologic and water quality benefits of having grass swales with an additional pre-treatment area and incorporation of check dams for managing highway runoff at a Maryland highway. These swales manage the hydrology of the stormwater by increasing the lag time (2-3 hours), reducing the overall average peak (32-44%) and reducing the total runoff volume (4-46%). The overall mass pollutant loads are reduced for TSS (38-62%), nitrate (92-95%), nitrite (54-71%), lead (78-82%), copper (56-70%) and zinc (67-79%). On the other hand, TKN (-120 to 44%), TP (-5 to 40%) and chloride (-61 to -4%) show mass increase. Compared to previous study, swales with check dams do not show any significant improvement over swales without check dams. However, a check dam swale with a pretreatment area has higher reduction of the overall mass pollutants removal for all pollutants except for TSS.