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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
271

Exploring Pedestrian Responsive Traffic Signal Timing Strategies in Urban Areas

Kothuri, Sirisha Murthy 25 July 2014 (has links)
The role of walking in the development of healthy, livable communities is being increasingly recognized. In urban areas, intersections represent locations where different modes converge, and are often viewed as deterrents to walking. This is due to the unwarranted and often unnecessary delays imposed by signal timing policies for pedestrians and increased potential for conflicts. Traditional signal timing design prioritizes vehicles over pedestrians leading to undesirable consequences such as large delays and risky pedestrian behaviors. Pedestrians are accommodated in a manner that is designed to cause least interruption to the flow of motor vehicles. This lack of pedestrian accommodation at signalized intersections is the focus of this dissertation. Understanding pedestrian attitudes and perceptions is important because it offers insights into actual crossing behavior at signalized intersections. An intercept survey of 367 crossing pedestrians was undertaken at four signalized intersections in Portland, Oregon, and binary logistic regression models were constructed to quantify the impacts of demographics, trip characteristics and type of infrastructure on pedestrian perceptions and attitudes regarding delay, crossing time and motivators for crossing decisions. Safety was found to have a larger effect than compliance on the decision to cross the street. Pedestrians at recall intersections expressed higher satisfaction with delay than at actuated intersections. Novel methods to measure pedestrian delay using 2070 signal controllers and Voyage software were developed. These methods have been adopted by the City of Portland to record actuation trends and delays at various intersections. In the absence of demand data, pedestrian push button actuations can be considered as a proxy for crossing demand. The micro-simulation software VISSIM was used to analyze delays resulting from varying pedestrian and vehicle volumes on a network of three intersections in Portland, Oregon. From a pedestrian perspective, free operation was found to be always beneficial due to lower pedestrian delays. However, from a system wide perspective, free operation was found to be beneficial only under low-medium traffic conditions from an overall delay reduction viewpoint, while coordinated operation showed benefits under heavy traffic conditions, irrespective of the volume of pedestrians. Control strategies were developed to identify the best mode of signal controller operation that produced the lowest overall average delay per user. A procedure to identify the optimal control strategy based on user inputs (major street volume to capacity ratios and rate of pedestrian phase serviced for the minor street) was developed. The procedure was applied to a network of three intersections in east Portland, OR and the findings were verified. This research offers significant contributions in the field of pedestrian research. The findings related to attitudes and perceptions of crossing pedestrians offer greater insights into pedestrian crossing behavior and add to the body of existing literature. The methods developed to obtain pedestrian actuations and delay data from signal controllers represent an easy and cost-effective way to characterize pedestrian service at intersections. The results pertaining to signal timing strategies represent an important step towards incorporating pedestrian needs at intersections and demonstrate how control strategies employed to benefit pedestrians could benefit the entire system.
272

Analysis of the Effects of Adaptive Ramp Metering on Measures of Efficiency with a Proposed Framework for Safety Evaluation

Loh, Jacky 01 June 2019 (has links) (PDF)
Adaptive ramp metering (ARM) is a widely popular intelligent transportation system (ITS) tool that boasts the ability to reduce congestion and streamline traffic flow during peak hour periods while maintaining a lower implementation cost than traditional methods such as freeway widening. This thesis explores the effectiveness of ARM implementation on an 18 mile segment of the Interstate 80 (I-80) corridor in the Bay Area residing in northern California. Smaller segments of this particular segment were analyzed to determine the effective length of ARM on efficiency at various lengths originating from a known bottleneck location. Efficiency values were also compared against a control segment of the Interstate 280 (I-280) in San Jose to provide a test site experiencing similar traffic congestion but without any ARM implementation. An Empirical Bayes analysis was conducted to provide the foundation of a safety evaluation of the ramp metering implementation and determine a counterfactual estimate of expected collisions had ARM implementation not occurred. It was found that the installation of the ramp meters did allow for some marginal increases in efficiency but may not be entirely associated with ARM implementation due to a variety of external factors as well as showing inconsistent behavior between analyzed segments. Regarding safety, the predictive model estimates 32.8 collisions to occur along a 0.5 mile segment within a three-year timeframe if ARM were not installed, which implies substantial improvements in safety conditions. However additional efficiency and safety data within the “after” period may be necessary to provide a more robust and conclusive evaluation as the ARM system is still relatively new.
273

Safety Effectiveness of Conversion of Two-Way-Left-Turn Lanes into Raised Medians

Alarifi, Saif 01 January 2014 (has links)
Two way left turn lanes (TWLTL) and raised medians are common median treatments on roadways. This research focused on evaluating the safety effectiveness of conversion of TWLTLs into raised medians using Before-After and Cross Sectional Studies. In the Before-After Studies, we evaluated the effect of this treatment using the Naive, Before-After with Comparison Group (CG), and Before-After with Empirical Bayes (EB) Methods. In order to apply these methods, a total of 33 segments of a treated group and 109 segments of a comparison group have been collected. Also, safety performance functions (SPFs) have been developed using the negative binomial model in order to calibrate crash modification factors (CMF) using the Before-After with Empirical Bayes Method. This research also evaluated the safety effectiveness of this treatment on four and six lane roads using Before-After with CG and Before-After with EB. The type of raised medians was further evaluated using Before-After with CG and EB. In sum, the results from this study show that applying the before-After and Cross Sectional studies have proved that the conversion from a TWLTL to a raised median helped to reduce total, fatal and injury, head on, angle, and left turn crashes. It significantly reduces crashes for head-on and left turn crashes, by restricting turning maneuvers. Also, this study has proved that the treatment is more effective on four rather than six lane roads. Furthermore, two types of raised medians, concrete and lawn curb, were evaluated after the conversion from TWLTLs. It was found that both medians have similar effects due to the conversion, and both median types helped in reducing the number of crashes.
274

An Enhanced Framework to Compute Road User Costs Associated with Construction Zones

Adebiyi, Jeremiah 01 August 2021 (has links)
The monetary quantification of inconveniences caused to the road users by ongoing construction activities is known as the Road Users Costs (RUCs). While the importance of RUCs is widely known, some highway agencies lack an appropriate methodology to compute RUCs. Thus, there is a need to develop a framework to compute RUCs that can be adopted quickly by highway agencies. This study reviewed existing literature and conducted a nationwide survey to identify and summarize the current practices of computing RUCs. It developed an enhanced framework and tool to compute RUCs that balances the effort required to calculate RUCs and the accuracy of the results. This enhanced framework accounts for the spatiotemporal variation of RUCs. The results of the study are expected to enable highway agencies to quickly and accurately compute RUCs to make better project management decisions, such as selecting the best contractor that minimizes the agency costs and RUCs.
275

Analyzing the Safety Effects of Edge Lane Roads for All Road Users

Lamera, Marcial F 01 September 2020 (has links) (PDF)
This thesis acts as one of the first studies that analyzes the safety effects of Edge Lane Roads (ELR) for all road users. This is important since ELRs can be a solution to many issues, such as alleviating congestion, increasing multimodality along roadways, and reducing maintenance costs. ELRs in both North America and Australia were observed. Starting with the North American ELRs, the following study designs were employed to estimate the safety of ELRs: (a) yoked comparison where each ELR installation was matched with at least two comparable 2-lane roads to serve as comparison sites and (b) an Empirical Bayes (EB) before/after analysis for ELR sites where requisite data on AADT and other relevant characteristics were available. Crash data was collected and compiled into four different groups: ELR before implementation, ELR after implementation, comparison site before ELR implementation, and comparison site after ELR comparison. The yoked comparison showed 9 of the 13 sites that had lower crash counts compared to their respective comparison sites. The EB analysis showed all 11 ELRs that were observed demonstrated a reduction in crashes. Moving to the Australian ELRs, the following study designs were employed: (c) analysis of general crash counts/trends, and (d) reverse EB analysis. The analysis of general crash counts and trends showed that each of the Australian ELRs exhibited very low amounts of crashes for 5 years, which further shows how safe these facilities are. Moving forward to the reverse EB analysis, 5 of the 8 ELR sites demonstrated a reduction in crashes. Overall, the results were generally favorable and indicated that ELRs provided a safer experience for cyclists, drivers, and pedestrians. More analysis is recommended as more data becomes available on these ELRs. Examples of this include using pedestrian and bicycle data to better understand the safety effects VRUs experience on North American facilities or gathering enough crash data to conduct 3-year reverse EB analyses for ELRs that were expanded to 2-lane roads. Hence, a recommendation can be made to implement a few experimental ELRs in rural locations throughout the State of California to help it meet its SB-1 objectives.
276

Measuring the Influence That Components Have on Pedestrian Route Choice in Activated Alleys

Gross, Samuel Hirsher 01 June 2015 (has links) (PDF)
This paper explores how cities have integrated formal planning into improving public space. Through a review of literature on the topic, this the paper identifies the potential design has to renovate narrow streets and alleys, within the public right of way. By preforming an assessment of plans and programs, this paper identifies the common themes or components that have been used by planners, architects, and engineers to improve the urban environment for pedestrians. Based on this information, a pilot study was created to measure the influence the most common components have on pedestrian route choice. The results are then compared to the information gathered from the assessed plans and programs. Suggestions for expanding the pilot study and other recommendations are presented upon the conclusion of this report.
277

Ridership Ramp-Up for Fixed-Guideway Transit Projects: An Evaluation of Initial Ridership Variation

Shinn, Jill Elizabeth 01 December 2018 (has links) (PDF)
Performance-based planning and programming has increased in popularity for transit project funding in recent years. This methodology focuses on quantitative performance measures to inform decision making. For transit projects, projections or observed ridership is the most commonly used performance measure to evaluate project benefits. Conventional wisdom within the transit industry suggests that measuring the performance of a transit project immediately after project opening may not capture all the project’s benefits, since it takes time for a project to realize its short-term ridership potential, a process commonly referred to as ridership ramp-up. While this idea is both intuitive and appealing, especially for projects that seem to be underperforming in their initial years, there is a need for empirical analysis to determine the typical magnitude and extent of ridership ramp up in order to better account for ramp-up in ridership forecasting and transit project evaluation. The purpose of this study is to meet this need by evaluating variations in ridership in the initial years after project opening for 55 fixed-guideway rail transit projects in the United States. I applied a fixed-effects regression model to predict one-year increases in ridership in each of the first five years after project opening, controlling for variation in gas prices, population, income, and unemployment. I find that ridership on new rail transit projects increases on average six percent controlling for other factors between the opening year and the first year after project opening. These findings can support decisions about how to account for ridership ramp up in forecasting and performance evaluation for rail transit projects.
278

Evaluating Urban Downtown One-Way to Two-Way Street Conversion Using Microscopic Traffic Simulation

Liu, Bernice 01 December 2019 (has links) (PDF)
Located in the heart of Silicon Valley, Downtown San Jose is attracting new residents, visitors, and businesses. Clearly, the mobility of these residents, visitors, and businesses cannot be accommodated by streets that focus on the single-occupancy automobile mode. To increase the potential for individuals to use non-single-occupancy modes of travel, the downtown area must have a cohesive plan to integrate multimodal use and public life. Complete streets are an integral component of the multi-modal transport system and more livable communities. Complete streets refer to roads designed to accommodate multiple modes, users, and activities including walking, cycling, transit, automobile, and nearby businesses and residents. A one-way to two-way street conversion is an example of a complete streets project. Similarly, tactical urbanism can provide cost-effective modifications (e.g., through temporary road closures for events like the farmers’ market) that enrich the public life in an urban environment. The ability to serve current and future transportation needs of residents, businesses and visitors through the creation of pleasant, efficient, and safe multimodal corridors is a guiding principle of a smart city. This research project addressed questions that guide the implementation of this overarching principle. These questions relate to travel patterns and potential network impacts of the conversion of the corridor(s) into complete streets. Towards that end, core network in downtown San Jose is simulated via a validated VISSIM model for 2015 traffic conditions (i.e., the base case or Scenario 0). Three scenarios are then modeled as variations to this model. The relevant model outputs from the base and scenario models provide easily digestible information the City can convey various impacts and trade-offs to partners and stakeholders prior to implementation of these plans. The scenarios modeled are based on stakeholder input. Microsimulation allows for detailed modeling and visualization of the transportation networks including movements of individual vehicles and pedestrians. The results based on 2040 traffic volumes provided by the city based on their long-range travel demand model clearly demonstrate that the existing network cannot support the projected level of travel demand. It indicates that the city needs an aggressive travel demand management program to curb the growth of automobile traffic. The output also includes 3-D animations of the traffic flow that can be used in public forums for community outreach. A discussion for such a campaign based on best practices around using these visualizations for public outreach is also provided. Located in the heart of Silicon Valley, Downtown San Jose is attracting new residents, visitors, and businesses. Clearly, the mobility of these residents, visitors, and businesses cannot be accommodated by streets that focus on the single-occupancy automobile mode. To increase the potential for individuals to use non-single-occupancy modes of travel, the downtown area must have a cohesive plan to integrate multimodal use and public life. Complete streets are an integral component of the multi-modal transport system and more livable communities. Complete streets refer to roads designed to accommodate multiple modes, users, and activities including walking, cycling, transit, automobile, and nearby businesses and residents. A one-way to two-way street conversion is an example of a complete streets project. Similarly, tactical urbanism can provide cost-effective modifications (e.g., through temporary road closures for events like the farmers’ market) that enrich the public life in an urban environment. The ability to serve current and future transportation needs of residents, businesses and visitors through the creation of pleasant, efficient, and safe multimodal corridors is a guiding principle of a smart city. This research project addressed questions that guide the implementation of this overarching principle. These questions relate to travel patterns and potential network impacts of the conversion of the corridor(s) into complete streets. Towards that end, core network in downtown San Jose is simulated via a validated VISSIM model for 2015 traffic conditions (i.e., the base case or Scenario 0). A number o Threef scenarios are then modeled as variations to this model. The relevant model outputs from the base and scenario models provide easily digestible information the City can convey various impacts and trade-offs to partners and stakeholders prior to implementation of these plans. The scenarios modeled are based on stakeholder input. Microsimulation allows for detailed modeling and visualization of the transportation networks including movements of individual vehicles and pedestrians. The results based on 2040 traffic volumes provided by the city based on their long-range travel demand model clearly demonstrate that the existing network cannot support the projected level of travel demand. It indicates that the city needs an aggressive travel demand management program to curb the growth of automobile traffic. The output also includes 3-D animations of the traffic flow that can be used in public forums for community outreach. A discussion for such a campaign based on best practices around using these visualizations for public outreach is also provided.
279

Inequity of access across America: A spatial, temporal, and modal disparity analysis

Maharjan, Sanju 09 December 2022 (has links) (PDF)
The overarching goal of this dissertation is to examine the spatial, temporal, and modal disparity of access across America. This is achieved by posing three research objectives. The first objective determines the spatial and temporal disparity of transit and automobile access gap, its impact on transit use, and its socioeconomic and built environment correlates. The second objective examines the spatial and temporal disparity of slightly and extremely risky bike infrastructure and measures the social inequity of access to bike infrastructure. The third objective indicates spatial transit access mismatch between high- and low-wage employment across metropolitans. Three findings are discerned. First, the access gap between transit and automobile has a disproportionate effect on African Americans, low-income households, millennials, and car-free households. Second, socially vulnerable communities residing African Americans, Hispanics, and car-free households have the least access to slightly risky bike infrastructure and yet the least prioritized in urban planning and bike infrastructure investments. Third, transit acts as a catalyst to widen spatial mismatch and discriminate socially vulnerable population particularly African Americans and car-free households
280

Measuring Accessibility for Pedestrians, Bicyclists, and Transit Riders to Grocery Stores in the Excelsior/Outer Mission Neighborhoods of San Francisco

Lee-Gardner, Alexandra 01 June 2022 (has links) (PDF)
Grocery stores are an important amenity in neighborhoods and access to grocery stores is important for health and well-being. While grocery store accessibility is a popular topic of research, studies measuring access for pedestrians, bicyclists, and transit riders are extremely rare. When a new store opened in the Excelsior/Outer Mission districts of San Francisco on a street lacking basic infrastructure for pedestrians, bicyclists, and transit riders, the importance of this study became apparent. The Excelsior/Outer Mission neighborhood has a shocking number of collisions (over 1,100 between 2015 and 2019), elevated levels of walking, biking, and transit ridership, and minimal safe infrastructure for these modes compared to other residential areas in San Francisco. To account for the effects of these conditions on accessibility, a rating system to measure infrastructure for users was used in addition to the more traditional gravity model. Combining results into a composite accessibility score highlights how using only a gravity model to measure accessibility may conceal some of the nuances of accessibility as perceived by pedestrians, bicyclists, and transit riders. While it appears from gravity indices that stores in the Excelsior/Outer Mission are only slightly less accessible, the sensitivity analysis shows that infrastructure can have a large effect on overall accessibility. Specifically in the Excelsior/Outer Mission neighborhood, with its rather low infrastructure scores, the higher the weight attributed to the importance of infrastructure the lower is composite accessibility. Rather than measuring accessibility using only travel time via a gravity model or other spatial model, this study shows the importance of combining physical proximity measurements with infrastructure information to provide a more complete picture. This is particularly important for those walking, biking, or riding transit where safety is an important consideration. This study provides one such way to include the unique considerations of pedestrians, bicyclists, and transit riders by including an infrastructure scoring system. Not only does this highlight the importance of including infrastructure measures, but it provides a framework for future infrastructure improvements around stores.

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