Browsing by Author "Murray-Tuite, Pamela M."

Now showing 1 - 13 of 13
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    An Agent-based Travel Demand Model System for Hurricane Evacuation Simulation
    Yin, Weihao (Virginia Tech, 2013-11-20)
    This dissertation investigates the evacuees' behavior under hurricane evacuation conditions and develops an agent-based travel demand model system for hurricane evacuation simulation using these behavioral findings. The dissertation econometrically models several important evacuation decisions including evacuate-stay, accommodation type choice, evacuation destination choice, evacuation mode choice, departure time choice, and vehicle usage choice. In addition, it explicitly considers the pre-evacuation preparation activities using activity-based approach. The models are then integrated into a two-module agent-based travel demand model system. The dissertation first develops the evacuate-stay choice model using the random-coefficient binary logit specification. It uses heterogeneous mean of the random parameter across households to capture shadow evacuation. It is found that the likelihood of evacuation for households that do not receive any evacuation notice decreases as their distance to coast increase on average. The distance sensitivity factor, or DSF, is introduced to construct the different scenarios of geographical extent of shadow evacuation. The dissertation then conducts statistical analysis of the vehicle usage choice. It identifies the contributing factors to households' choice of the number of vehicles used for evacuation and develop predictive models of this choice that explicitly consider the constraint imposed by the number of vehicles owned by the household. This constraint is not accommodated by ordered response models. Data comes from a post-storm survey for Hurricane Ivan. The two models developed are variants of the regular Poisson regression model: the Poisson model with exposure and right-censored Poisson regression. The right-censored Poisson model is preferred due to its inherent capabilities, better fit to the data, and superior predictive power. The multivariable model and individual variable analyses are used to investigate seven hypotheses. Households traveling longer distances or evacuating later are more likely to use fewer vehicles. Households with prior hurricane experience, greater numbers of household members between 18 and 80, and pet owners are more likely to use a greater number of vehicles. Income and distance from the coast are insignificant in the multivariable models, although their individual effects have statistically significant linear relationship. However, the Poisson based models are non-linear. The method for using the right-censored Poisson model for producing the desired share of vehicle usage is also provided for the purpose of generating individual predictions for simulation. The dissertation then presents a descriptive analysis of and econometric models for households' pre-evacuation activities based on behavioral intention data collected for Miami Beach, Florida. The descriptive analysis shows that shopping - particularly food, gasoline, medicine, and cash withdrawal - accounts for the majority of preparation activities, highlighting the importance of maintaining a supply of these items. More than 90% of the tours are conducted by driving, emphasizing the need to incorporate pre-evacuation activity travel into simulation studies. Households perform their preparation activities early in a temporally concentrated manner and generally make the tours during daylight. Households with college graduates, larger households, and households who drive their own vehicles are more likely to engage in activities that require travel. The number of household members older than 64 has a negative impact upon engaging in out-of-home activities. An action day choice model for the first tour suggests that households are more likely to buy medicine early but are more likely to pick up friends/relatives late. Households evacuating late are more likely to conduct their activities late. Households with multiple tours tend to make their first tour early. About 10% of households chain their single activity chains with their ultimate evacuation trips. The outcomes of this paper can be used in demand generation for traffic simulations. The dissertation finally uses the behavioral findings and develops an agent-based travel demand model system for hurricane evacuation simulation, which is capable of generating the comprehensive household activity-travel plans. The system implements econometric and statistical models that represent travel and decision-making behavior throughout the evacuation process. The system considers six typical evacuation decisions: evacuate-stay, accommodation type choice, evacuation destination choice, mode choice, vehicle usage choice and departure time choice. It explicitly captures the shadow evacuation population. In addition, the model system captures the pre-evacuation preparation activities using an activity-based approach. A demonstration study that predicts activity-travel patterns using model parameters estimated for the Miami-Dade area is discussed. The simulation results clearly indicate the model system produced the distribution of choice patterns that is consistent with sample observations and existing literature. The model system also identifies the proportion of the shadow evacuation population and their geographical extent. About 23% of the population outside the designated evacuation zone would evacuate. The shadow evacuation demand is mainly located within 3.1 miles (5 km) of the coastline. The output demand of the model system works with agent-based traffic simulation tools and conventional trip-based simulation tools. The agent-based travel demand model system is capable of generating activity plans that works with agent-based traffic simulation tools and conventional trip-based simulation tools. It will facilitate the hurricane evacuation management.
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    A Cellular Automata Approach to Estimate Incident-Related Travel Time on Interstate 66 in Near Real Time
    Wang, Zhuojin; Murray-Tuite, Pamela M. (Virginia Center for Transportation Innovation and Research, 2010-03-01)
    Incidents account for a large portion of all congestion and a need clearly exists for tools to predict and estimate incident effects. This study examined (1) congestion back propagation to estimate the length of the queue and travel time from upstream locations to the incident location and (2) queue dissipation. Shockwave analysis, queuing theory, and cellular automata were initially considered. Literature indicated that shockwave analysis and queuing theory underestimate freeway travel time under some conditions. A cellular automata simulation model for I-66 eastbound between US 29 and I-495 was developed. This model requires inputs of incident location, day, time, and estimates of duration, lane closures and timing, and driver re-routing by ramp. The model provides estimates of travel times every 0.2 mile upstream of the incident at every minute after the start of the incident and allows for the determination of queue length over time. It was designed to be used from the beginning of the incident and performed well for normal conditions and incidents, but additional calibration was required for rerouting behavior. We recommend that the Virginia Department of Transportation (1) further pursue cellular automata approaches for near-real time applications along freeways; and (2) consider adopting an approach to address detector failures and errors. Adopting these recommendations should improve VDOT's freeway real-time travel time estimation and other applications based on detector data.
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    Characterization and Assessment of Transportation Diversity: Impacts on Mobility and Resilience Planning in Urban Communities
    Rahimi Golkhandan, Armin (Virginia Tech, 2020-06-25)
    A transportation system is a critical infrastructure that is key for mobility in any community. Natural hazards can cause failure in transportation infrastructure and impede its routine performance. Ecological systems are resilient systems that are very similar to transportation systems. Diversity is a fundamental factor in ecological resilience, and it is recognized as an important property of transportation resilience. However, quantifying transportation diversity remains challenging, which makes it difficult to understand the influence of diversity on transportation performance and resilience. Consequently, three studies are undertaken to remedy this circumstance. The first study develops a novel approach – inspired by biodiversity in ecological stability theory – to characterize and measure transportation diversity by its richness (availability) and evenness (distribution). This transportation diversity approach is then applied to New York City (NYC) at the zip code level using the GIS data of transportation modes. The results demonstrate the variation of transportation diversity across the city. The characterized inherent and augmented complementarities start to uncover the dynamics of modal compensation and to demonstrate how transportation diversity contributes to this phenomenon. Moreover, the NYC zip codes with low transportation diversity are mainly in hurricane evacuation zones that are more vulnerable. Consequently, low transportation diversity in these areas could affect their post-disaster mobility. In the second study, the influence of transportation diversity on post-disaster mobility is examined by investigating the patterns of mobility in New York City one month before and after Hurricane Sandy using Twitter data. To characterize pre- and post-Sandy mobility patterns, the locations that individuals visited frequently were identified and travel distance, the radius of gyration, and mobility entropy were measured. Individuals were grouped according to the transportation diversity of their frequently visited locations. The findings reveal that individuals that lived in or visited zip codes with higher transportation diversity mostly experienced less disturbance in their mobility patterns after Sandy and the recovery of their mobility patterns was faster. The results confirm that transportation diversity affects the resilience of individual post-disaster mobility. The approach used in this study is one of the first to examine the root causes of changes in mobility patterns after extreme events by linking transportation infrastructure diversity to post-disaster mobility. Finally, the third study employs the transportation diversity approach to investigate modal accessibility and social exclusion. Transportation infrastructure is a sociotechnical system and transport equity is crucial for access to opportunities and services such as jobs and infrastructure. The social exclusion caused by transport inequity could be intensified after natural disasters that can cause failure in a transportation system. One approach to determine transport equity is access to transportation modes. Common catchment area approaches to assess the equity of access to transportation modes cannot differentiate between the equity of access to modes in sub-regions of an area. The transportation diversity approach overcomes this shortcoming, and it is applied to all transportation modes in NYC zip codes to measure the equity of access. Zip codes were grouped in quartiles based on their transportation diversity. Using the American Community Survey data, a set of important socioeconomic and transport usage factors were compared in the quartile groups. The results indicated the relationship between transportation diversity and income, vehicle ownership, commute time, and commute mode. This relationship highlighted that social exclusion is linked with transport inequity. The results also revealed that the inequity of the transport system in zip codes with low transportation diversity affects poor individuals more than non-poor and the zip codes with a majority of black and Hispanic populations are impacted more. Further consideration of the impacts of Hurricanes Irene and Sandy in NYC shows that people in areas with a lower transportation diversity were affected more and the transport inequity in these areas made it difficult to cope with these disasters and caused post-disaster social exclusion. Therefore, enhancing transportation diversity should support transport equity and reduce social exclusion under normal situations and during extreme events. Together, these three studies illustrate the influence of transportation diversity on the resilience of this infrastructure. They highlight the importance of the provision and distribution of all transportation modes, their influence on mobility during normal situations and extreme events and their contribution toward mitigating social exclusion. Finally, these studies suggest that transportation diversity can contribute to more targeted and equitable transportation and community resilience planning, which should help decision-makers allocate scarce resources more effectively.
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    A Conceptual Framework for an Enterprise-Wide Geospatially Enabled Information Management System for Transportation Right-Of-Way Business Processes
    Sambana, Kavya (Virginia Tech, 2010-05-13)
    Right-of-way business processes have been identified as one of the areas where information bottlenecks occur in transportation agencies, not only because of the amount of information involved, but also because of the interdependent nature of these activities. Transportation projects are associated with parcels whose status change during and after the project based on information from right-of-way activities. Geospatially enabled decision making tools enhance data interpretation as well as data retrieval of this information. By using enterprise-level applications, information sharing between the transportation agency, other jurisdictions, and the public becomes more efficient. Being able to quickly visualize the status of parcels in a geospatial environment further enhances the management of resources which, in turn, improves timely project delivery. This thesis presents a conceptual framework for an information management system and its geospatial enablement through a logical model for Geospatial Decision Making Activities (GDMA) in transportation right-of-way offices. The logical model for GDMA, presented in Unified Modeling Language, includes state machine diagram and data flow diagram models for tracking the parcel and capturing the geospatial enablement of right-of-way activities.
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    Estimating Pedestrian Crashes at Urban Signalized Intersections
    Kennedy, Jason Forrest (Virginia Tech, 2008-12-10)
    Crash prediction models are used to estimate the number of crashes using a set of explanatory variables. The highway safety community has used modeling techniques to predict vehicle-to-vehicle crashes for decades. Specifically, generalized linear models (GLMs) are commonly used because they can model non-linear count data such as motor vehicle crashes. Regression models such as the Poisson, Zero-inflated Poisson (ZIP), and the Negative Binomial are commonly used to model crashes. Until recently very little research has been conducted on crash prediction modeling for pedestrian-motor vehicle crashes. This thesis considers several candidate crash prediction models using a variety of explanatory variables and regression functions. The goal of this thesis is to develop a pedestrian crash prediction model to contribute to the field of pedestrian safety prediction research. Additionally, the thesis contributes to the work done by the Federal Highway Administration to estimate pedestrian exposure in urban areas. The results of the crash prediction analyses indicate the pedestrian-vehicle crash model is similar to models from previous work. An analysis of two pedestrian volume estimation methods indicates that using a scaling technique will produce volume estimates highly correlated to observed volumes. The ratio of crash and exposure estimates gives a crash rate estimation that is useful for traffic engineers and transportation policy makers to evaluate pedestrian safety at signalized intersections in an urban environment.
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    Examination of Taxi Travel Patterns in Arlington County
    Nicholas, Joshua Stephen (Virginia Tech, 2012-04-27)
    This research focuses on utilizing the typically overlooked taxi manifest data to analyze taxi operations with respect to transit, and also presents alternative uses for the data in transportation planning. Taxi travel characteristics are explored for Arlington, Virginia, a county containing both urban and suburban qualities. Previous research contends that manifest data can provide valuable quantitative descriptors of taxi travel. This thesis attempts to describe taxi travel by quantifying trip characteristics; the shortcomings of using manifest data are discussed and the results are reported. The taxi operations results are then compared for weekend and weekday travel and also for airport and non-airport bound travel. Several key differences between these groups of taxi trips are discussed. Next, an investigation of the relationship between mass transit facilities and taxi travel is conducted. Because taxis provide a complementary yet competing public transportation service to mass transit, it is hypothesized that examining the proximity to transit options and the timing of taxi trips can provide insight to the perceived gaps in mass transit services. However, the data show that simply examining geographic or temporal characteristics of taxi trips does not define clear relationships between transit facilities and taxi use. Instead, the results suggest that other variables such as land use and vehicle access may hold a greater influence over the generation of taxi trips. Despite the difficulty in using manifest data to determine gaps in transit, the data collected by taxi regulators could have numerous applications for planners. Possible applications for the type of taxi data used in this research are explored and a potential data flow for agencies is proposed.
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    Human Factors Evaluation of an In-Vehicle Active Traffic and Demand Management (ATDM) System
    Sykes, Kayla Paris (Virginia Tech, 2016-04-04)
    This research study focused on the development and subsequent evaluation of an in-vehicle Active Traffic and Demand Management (ATDM) system deployed on I-66. The ATDM elements inside the vehicle allowed drivers to remain consistently aware of traffic conditions and roadway requirements even if external signage was inaccessible. Forty participants were accompanied by a member of the research team and experienced the following features from the in-vehicle device (IVD): 1) dynamic speed limits, 2) dynamic lane use/shoulder control, 3) High Occupancy Vehicle (HOV) restrictions, and 4) variable message signs (VMS). This system was equipped with auditory and visual alerts to notify the driver when relevant information was updated. The research questions addressed distraction, desirability, and driver behavior associated with the system. Participant data was collected from the instrumented vehicle, various surveys, and researcher observation. Analysis of Variance (ANOVA) and Tukey-Kramer tests were performed to analyze participant eye glance durations towards the IVD and instrument cluster. Wilcoxon signed rank tests were used to draw conclusions from participant speed data and some survey responses. Several key findings were uncovered related to each research category: 1) the IVD would not be classified as a distraction according to NHTSA distraction guidelines, 2) seventy-three percent of participants would want the in-vehicle technology in their next vehicle, and 3) the speed limit alert motivated participants to alter their speed (based on both survey results and actual participant speed data).
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    Improving Dilemma Zone Protection Control Issues at Signalized Intersection Using a Web-Game
    Kasaraneni, Yatish (Virginia Tech, 2009-09-04)
    Web games provide a platform for creative instructional activities that can capture the students' attention towards the course. These games can be used to emulate the realistic situations which can be used as effective lab experiments that could give the students a hands-on experience using real world scenarios. This thesis presents an innovative web-based game developed for the demonstration of the driver-behavior at signalized intersections that can be used as a supplementary tool for the Transportation Engineering course. The game format is carefully designed to supplement the understanding of the class learning material through a fun environment. It was designed to be widely accessible through the internet and have an attractive user interface and was improved from the feedback obtained from the pilot study. The game is programmed on the .NET Framework using the Microsoft Visual C# as a core programming language, ASP to develop the web interface, and Microsoft Access as the databases for the program. The thesis also provides a methodological framework for collecting data about student engagement in a course and in particular presents the data collection procedure used in Transportation Engineering Course (CEE 4609). The collected data was analyzed to find the student engagement in the course after the introduction of the game. The thesis gives the conclusions drawn from the research with insights into possible drawbacks and scope for future improvements.
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    Integrating Geospatial Technologies into the Property Management Process of the Transportation Right-Of-Way
    Ghanta, Neelima (Virginia Tech, 2007-02-05)
    Property Management, one functional area within Right-of-Way offices in state transportation agencies, is responsible for managing the property acquired for highway projects. These activities are data and document intensive and efficiency for performing them would be improved through the implementation of an information management system. Because of the geospatial nature of many of these activities, geographic information systems (GIS) would increase the effectiveness of this system. A literature review and survey were conducted to understand the current state of practice for the use of GIS and information management systems in Property Management. There is no identified comprehensive system that covers all Property Management activities. An initial step in developing a geospatially-enabled enterprise-level information management system, a logical model was developed. This included developing the business process diagram, business process models, and use case models based on the principles of systems engineering using the Computer Aided Software (CASE) Enterprise Architecture. Activities that would benefit from a geospatial component have been identified and included in the models. The developed models have been validated by working with PennDOT staff. The resulting model serves as a standard template for state transportation agencies and helps conceptualize the advantages of integration and interaction with other systems, and geospatial enablement prior to investment in an information management system.
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    Low Profile, Printed Circuit, Dual-Band, Dual-Polarized Antenna Elements and Arrays
    Dorsey, William Mark (Virginia Tech, 2009-04-03)
    Dual-band antenna elements that support dual-polarization provide ideal performance for applications including space-based platforms, multifunction radar, wireless communications, and personal electronic devices. In many communications and radar applications, a dual-band, dual-polarization antenna array becomes a requirement in order to produce an electronically steerable, directional beam capable of supporting multiple functions. The multiple polarizations and frequency bands allow the array to generate multiple simultaneous beams to support true multifunction radar. Many of the applications in spaced-based systems and personal electronic devices have strict restraints on the size and weight of the antenna element, favoring a low-profile, lightweight device. The research performed in this dissertation focuses on the design of a dual-band, dual-polarized antenna element capable of operating as an isolated element or in an array environment. The element contains two concentric, dual-polarized radiators. The low band radiator is a shorted square ring antenna, and the high band radiator is a square ring slot. Each constituent element achieves circular polarization through the introduction of triangular perturbations into opposing corners of the radiating element. This technique has been shown to introduce two, near-degenerate modes in the structure that – when excited in phase quadrature – combine to form circular polarization. The perturbations allow circular polarized operation with only a single feed point. The sense of the circular polarization is determined by the location of the feed point with respect to the perturbations. Both senses of circular polarization are excited by the introduction of orthogonal feeds for each of the two radiating elements. Thus, dual-ban, dual-circular polarization is obtained. The element achieves a low-profile from its printed circuit board realization. The high band square ring slot is realized in stripline. The orthogonal feeding transmission lines are printed on opposing sides of an electrically thin dielectric layer to allow them to cross without physically intersecting. This thin feeding substrate is sandwiched between two dielectric layers of matched dielectric constant. A ground plane is located on the top and bottom of the sandwiched dielectric structure, and the top ground plane contains the square ring slot with perturbed corners. Slotted stripline structures have been shown in the literature to excite a parallel-plate mode that can degrade overall performance of the antenna. Plated through holes are introduced at the outer perimeter of the square ring slot to short out this parallel-plate mode. The plated through holes (also called vias) serve as the shorting mechanism for the low band microstrip shorted square ring radiator. This element also contains triangular perturbations at opposing corners to excite circular polarization with a single feed point. In this element, orthogonal probe feeds are present to excite both senses of circular polarization. A dual-band, dual-polarized antenna element was built, tested, and compared to simulations. The constructed element operated at two distinct industrial, scientific, and medical (ISM) frequency bands due to their popularity in low power communications. The antenna element was realized in a multilayer printed circuit layout. A complex design procedure was developed and submitted to a printed circuit board company who manufactured the antenna element. The s-parameters of the antenna were measured using a Network Analyzer, and the results show good agreement with simulations. The radiation and polarization characteristics were measured in a compact range facility. These results also agreed well with simulations. The measured results verify the simulation models that were used in the simulations and establish a confidence level in the feasibility of constructing this element. The dual-band, dual-polarization nature of this element was established through the construction and measurement of this element. A novel size reduction technique was developed that allows for significant reduction of the element's footprint. This size reduction facilitates the placement of this element within an array environment. The loading technique utilizes a structure analogous to a parallel-plate capacitor to drastically reduce the overall size of the low frequency shorted square ring. The loading structure uses a substrate that is separate from that of the radiating elements. This allows the load to use a high dielectric material to achieve a high capacitance without requiring the radiating elements to be printed on high dielectric material that is potentially expensive and lossy at microwave frequencies. The two frequency bands were selected to be in separate industrial, scientific, and medical (ISM) bands. These frequency bands are increasingly popular in low power communication devices because unlicensed operation is permitted. The 2.45 GHz and 5.8 GHz ISM bands are commonly used for applications including Bluetooth technology, multiple 801.11 protocol, cellular phone technology, and cordless phones. The ISM bands were chosen for this antenna element due to their popularity, but this antenna is not restricted to these bands. The frequency ratio can be altered by controlling the dielectric constant used in the printed circuit board design, the parameters of the capacitive loading structure, and the size of the constituent elements that are used. After the size reduction technique is applied, the dual-band, dual-polarized elements can be placed in an array environment resulting in an array capable of generating both senses of circular polarization in the two, distinct ISM bands. This provides an aperture capable of supporting multiple functions. Depending on the applications required, the frequency bands of the antenna element can be altered to suit the particular system needs. The array analysis performed in this dissertation used a unique hybrid calculation technique that utilizes nine active element patterns to represent the patterns of the individual elements within a large antenna array. A common first look at array performance is achieved by multiplying the element pattern of an isolated element by an array factor containing the contributions of the geometrical arrangement of the antenna elements. This technique neglects mutual coupling between elements in the array that can alter the impedance match and radiation characteristics of the elements in the array. The active element pattern defines the radiation pattern of a given element in an array when all other elements are terminated in a matched impedance load. The active element pattern is unique for each element in an array. When these patterns are summed, the exact array pattern is obtained. While this technique has the advantage of accuracy, it is not ideal because it requires the simulation, calculation, or measurement of the pattern for each element in the array environment. The technique developed in this dissertation uses only nine active element patterns. These elements are then assigned to represent the active element patterns for all elements in the array depending on the geometrical region where the given element resides. This technique provides a compromise between the speed of using a single element pattern and the accuracy of using the unique active element pattern for each element in the array. The application of these two concentric, coplanar radiators along with the capacitive loading technique provides a unique contribution to the field of antenna engineering. The majority of dual-band antenna elements in the literature operate with a single polarization in each band. The ones that operate with dual-polarization in each band are typically limited to dual-linear polarization. Circular polarization is preferable to linear in many applications because it allows flexible orientation between the transmitting antenna and receiving antenna in a communications system, while also mitigating multipath effects that lead to signal fading. The ability to operate with two, orthogonal senses of circular polarization allows a system to reuse frequencies and double system capacity without requiring additional bandwidth. The uniqueness of this element lies in its ability to provide dual-circular polarization in two separate frequency bands for an individual element or an antenna array environment. The arrangement of the two element geometries with the addition of the novel capacitive loading technique is also unique. The performance of this element is achieved while maintaining the light weight, low profile design that is critical for many wireless communications applications. This dissertation provides a detailed description of the operation of this dual-band, dual-polarized antenna element. The design of the constituent elements is discussed for several polarization configurations to establish an understanding of the building blocks for this element. The dual-band, dual-polarized element is presented in detail to show the impedance match, isolation, and axial ratio performance. The capacitive loading technique is applied to the dual-band, dual-polarized element, and the performance with the loading in place is compared to the performance of the unloaded element. Next, there is an in-depth description of the array calculation technique that was developed to incorporate mutual coupling effects into the array calculations. This technique is then applied to the dual-band, dual-polarized array to show the performance of several array sizes.
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    Microscopic Control Delay Modeling at Signalized Arterials Using Bluetooth Technology
    Rajasekhar, Lakshmi (Virginia Tech, 2011-12-05)
    Real-time control delay estimation is an important performance measure for any intersection to improve the signal timing plans dynamically in real-time and hence improve the overall system performance. Control delay estimates helps to determine the level-of-service (LOS) characteristics of various approaches at an intersection and takes into account deceleration delay, stopped delay and acceleration delay. All kinds of traffic delay calculation especially control delay calculation has always been complicated and laborious as there never existed a low-cost direct method to find them in real-time from the field. A recent validated technology called Bluetooth Median Access Control (MAC) ID matching traffic data collection technology seems to hold promise for continuous and cost-effective traffic data collection. Bluetooth traffic data synchronized with vehicle trajectory plot generated from GPS probe vehicle runs has been used to develop control delay models which has a potential to predict the control delays in real-time based on Bluetooth detection error parameters in field. Incorporating control delay estimates in real-time traffic control management would result in significant improvement in overall system performance.
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    Sustainable Pavement Construction: Developing a methodology for integrating environmental impact into the decision making process
    Highfield, Crysta Lynn (Virginia Tech, 2011-04-27)
    Sustainability and specifically environmental stewardship are emerging as prominent issues in engineering decision-making. Despite this, the United States has neither a national policy on sustainability, nor a national sustainable transportation strategy. In many cases this has resulted in state DOTs basing their environmental practices on requirements set out previously by EPA regulations with little or no additional consideration of environmental effects. A survey conducted as part of this thesis revealed that environmental stewardship is not considered part of current DOT pavement management engineers' job responsibilities, despite having duties such as pavement design and maintenance which can greatly affect the environmental impact of a project. Initial cost and engineering judgment were the most widely considered in decision-making, with LCCA also being considered at least some of the time by most respondents. Environmental impacts, on the other hand, are not often integrated into formal decision making and are more likely to be considered as a "tie breaker" when alternatives have similar costs. The literature review also covered two distinct types of environmental decision support tools: Environmental Rating Tools and Environmental Impact Calculators. Rating Tools gather predominantly environmental impact information in order to award a score to a project. Environmental Calculators are software tools that use material or equipment inputs to estimate the amount of pollutants produced by a project. While a variety of environmental impact tools are currently available they suffer from drawbacks such as incomplete or unclearly defined LCA boundaries, consideration of only one environmental impact, subjectivity, lack of transparency, out-of-date databases, and an inability to perform probabilistic calculations. CO₂e was the only environmental factor considered by nearly all Environmental Calculators reviewed as part of this thesis and was a major focus of the Rating Tools. The thesis proposes the framework for a tool that addresses some of the limitations of available tools and aids decision-makers in incorporating environmental factors into roadway decision-making. The proposed tool would address many of the limitations of previous environmental impact calculators and could be implemented without the need for extensive additional research. The tool would calculate emissions due to material extraction and production, emissions due to construction activities, resource consumptions, and emissions due to work zone delays. Emissions due to work zone delays are not considered by any other currently available tool. The tool would also perform probabilistic calculations and have a database which could be added to and updated by users. Additional products developed as part of this thesis are a review of currently available environmental impact tools and a Microsoft Excel workbook used to demonstrate the intended usage of the tool. It is concluded that the development of such a tool is necessary and feasible. The proposed tool would address limitations of available tools by considering more than one environmental impact, including the previously neglected impact of emissions due to work zone related delay, pairing a user-friendly interface with an editable database, and supporting probabilistic calculations. Recommended future research includes surveying state DOT engineers to determine the barriers delaying implementation of currently available environmental impacts tools. Further benefits could be realized by programming the proposed tool and building a database that reflects the materials, mixes, and construction activities available to a specific locality.
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    A Transport Justice Evaluation of Employer-Based Transit Subsidies
    Hamre, Andrea Katherine Marie (Virginia Tech, 2018-01-24)
    National statistics regarding subsidized commuting suggest that employer-based transit subsidies may be inaccessible to the vast majority of the working poor. My main purpose with this study is to increase our understanding of employer-based transit subsidies from a transport justice perspective. I apply the theory of transport justice developed by Karel Martens to evaluate whether the provision of transit subsidies varies significantly by income, and whether the subsidies are significantly associated with accessibility as measured by daily trip levels. I use worker-level data from household travel surveys for 10 of the 22 largest MPOs in the U.S., organized into 7 cases: 1) Atlanta; 2) Baltimore and Washington, DC; 3) Denver; 4) Los Angeles and San Diego; 5) New York and Newark; 6) Philadelphia; and 7) San Francisco. In each of the 7 cases, the odds of being offered a transit subsidy were significantly lower for workers in the 1st income quintile compared to workers in the 4th and 5th income quintiles, even after controlling for other relevant worker and employer characteristics. I found a lack of evidence, in most cases, that transit subsidies are significantly associated with accessibility, both in terms of daily trip levels for low-income workers and daily trip differentials between income groups. Given my finding that low-income workers are the least likely to have access to employer-based transit subsidies, policymakers may consider reform alternatives, such as commuter benefit ordinances, a refundable tax credit for commuting expenses, or alternatives such as income- and location-based subsidies for transit that may support all trip purposes. I hope this study will serve as a reference for policymakers deliberating commuter benefit reforms as well as strategies to support affordable access to opportunities for the working poor.