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Articles 1891 - 1920 of 2758
Full-Text Articles in Engineering
Bring Your Own Water Treatment System: United States Patent, Evan A. Thomas, Maximilian Gold
Bring Your Own Water Treatment System: United States Patent, Evan A. Thomas, Maximilian Gold
Mechanical and Materials Engineering Faculty Publications and Presentations
A method and apparatus for filtering a fluid is presented. In one embodiment, the apparatus converts contaminated water into water having a lower turbidity and bacterial contamination level than the contaminated water. The apparatus includes a settling unit for at least partially settling a portion of the water; a filter unit having a filtration media; wherein the filtration media comprises sand, anthracite coal, burnt rice husks, diatomaceous earth, gravel, pumice gravel, or combinations thereof; a sanitation unit; wherein the sanitation unit is an ultraviolet disinfection unit; a backwash unit; wherein the settling unit is in fluid communications with the filter …
Determination Of The Electric Field Intensity And Space Charge Density Versus Height Prior To Triggered Lightning, Christopher J. Biagi, Martin A. Uman, Jay Gopalakrishnan, J. D. Hill, Vladimir A. Rakov, T. Ngin, Douglas M. Jordan
Determination Of The Electric Field Intensity And Space Charge Density Versus Height Prior To Triggered Lightning, Christopher J. Biagi, Martin A. Uman, Jay Gopalakrishnan, J. D. Hill, Vladimir A. Rakov, T. Ngin, Douglas M. Jordan
Mathematics and Statistics Faculty Publications and Presentations
We infer the vertical profiles of space charge density and electric field intensity above ground by comparing modeling and measurements of the ground-level electric field changes caused by elevating grounded lightning-triggering wires. The ground-level electric fields at distances of 60 m and 350 m were measured during six wire launches that resulted in triggered lightning. The wires were launched when ground-level electric fields ranged from 3.2 to 7.6 kV m−1 and the triggering heights ranged from 123 to 304 m. From wire launch time to lightning initiation time, the ground-level electric field reduction at 60 m ranged from 2.2 …
Interview With Adam Boesel, Green Micro Gym, 2011 (Audio), Adam Boesel
Interview With Adam Boesel, Green Micro Gym, 2011 (Audio), Adam Boesel
All Sustainability History Project Oral Histories
Interview of Adam Boesel by Teresa Celestine at Green Micro Gym Portland, Oregon on July 29th, 2011.
The interview index is available for download.
Social Innovation Concepts At Nasa: Integrating International Development Challenges And Hands-On Prototyping With Spacecraft Design Training, Leonard Yowell, Evan A. Thomas
Social Innovation Concepts At Nasa: Integrating International Development Challenges And Hands-On Prototyping With Spacecraft Design Training, Leonard Yowell, Evan A. Thomas
Mechanical and Materials Engineering Faculty Publications and Presentations
The NASA Johnson Space Center Social Innovation program has been designed to encourage innovation within the NASA community that benefits both NASA's core mission as well as human needs domestically and internationally. By encouraging internal and external collaboration and providing resources including the new Johnson Space Center "Sandbox" design shop, new innovations are anticipated. Technologies developed for the human exploration of space share similar requirements with appropriate technology for the developing world. The technology goals of keeping people alive in a difficult environment involve addressing requirements for low maintenance and robustness and often include using renewable energy sources. Technologies developed …
A System Dynamics Model Of Pharmaceutical Opioids: Medical Use, Diversion, And Nonmedical Use, Teresa Schmidt, Wayne Wakeland, J. David Haddox
A System Dynamics Model Of Pharmaceutical Opioids: Medical Use, Diversion, And Nonmedical Use, Teresa Schmidt, Wayne Wakeland, J. David Haddox
Complex Systems Faculty Publications and Presentations
A dramatic rise in the nonmedical of pharmaceutical opioids has presented the United States with a substantial public health problem. Nonmedical use of prescription pain relievers has become increasingly prevalent in the US over the last two decades, and diversion of medicines obtained by prescription is assumed to be a major source of supply for nonmedical opioid use. Policymakers striving to protect population health by ameliorating the adverse outcomes of nonmedical use of opioid analgesics could benefit from a systems-level model which reflects the complexity of the system and incorporates the full range of available data. To address this need, …
Calibration Of Complex System Dynamics Models: A Practioner's Report, Rod Walker, Wayne Wakeland
Calibration Of Complex System Dynamics Models: A Practioner's Report, Rod Walker, Wayne Wakeland
Complex Systems Faculty Publications and Presentations
This paper is not a typical academic paper that is solidly grounded in the literature. Instead, this paper reports practitioner’s experiences in rebuilding and calibrating a very large system dynamics model. A prior version of this model had been in use for over 10 years in an ongoing executive training simulation. That model had never worked correctly in several key areas, requiring the outputs to be manually adjusted by very experienced facilitators during the course of the simulation. The present project rebuilt the system dynamics model, redesigned the parts that weren’t working, and calibrated the resulting model to match the …
Sustainable Oxygen: A Low Power Approach For Providing Emergency Medical Oxygen For Spacecraft And Hospitals In Developing Countries, Anndee L. Huff, Evan Rhead, Zdenek Zumr, Evan A. Thomas
Sustainable Oxygen: A Low Power Approach For Providing Emergency Medical Oxygen For Spacecraft And Hospitals In Developing Countries, Anndee L. Huff, Evan Rhead, Zdenek Zumr, Evan A. Thomas
Mechanical and Materials Engineering Faculty Publications and Presentations
An oxygen concentrator targeting an 80% reduction in power demand over commercial systems is being developed using a pressure swing adsorption process. This system is targeted for a service interval five times longer than commercial systems, and is tolerant to high humidity environments- the leading cause of device failure in developing countries. This system could provide emergency medical oxygen in a spacecraft without increasing oxygen concentration in the vehicle. Flight surgeons seek this capability, but presently, there is no system that meets power, size, and delivery rate requirements. This type of system is also well suited for medical oxygen in …
Striation-Based Beamforming For Estimating The Waveguide Invariant With Passive Sonar, Lisa M. Zurk, Daniel Rouseff
Striation-Based Beamforming For Estimating The Waveguide Invariant With Passive Sonar, Lisa M. Zurk, Daniel Rouseff
Electrical and Computer Engineering Faculty Publications and Presentations
The waveguide invariant summarizes the pattern of constructive and destructive interference between acoustic modes propagating in the ocean waveguide. For many sonar signal-processing schemes, it is essential to know the correct numerical value for the waveguide invariant. While conventional beamforming can estimate the ratio between the waveguide invariant and the range to the source, it cannot unambiguously separate the two terms. In the present work, striationbased beamforming is developed. It is shown that the striation-based beamformer can be used to produce an estimate for the waveguide invariant that is independent of the range. Simulation results are presented.
Evolving Machine Morality Strategies Through Multiagent Simulations, David Burke
Evolving Machine Morality Strategies Through Multiagent Simulations, David Burke
Systems Science Friday Noon Seminar Series
There is a general consensus among robotics researchers that the world of the future will be filled with autonomous and semi-autonomous machines. There is less of a consensus, though, on the best approach to instilling a sense of 'machine morality' in these systems so that they will be able to have effective interactions with humans in an increasingly complex world. In my talk, we take a brief look at some existing approaches to computational ethics, and then describe work we've undertaken creating multiagent simulations involving moral decision-making during strategic interactions. In these simulations, agents make choices about whether to cooperate …
Assessment Of Statewide Intersection Safety Performance, Christopher M. Monsere, Todd Johnson, Karen Dixon, Jianfei Zheng, Ida Schalkwyk
Assessment Of Statewide Intersection Safety Performance, Christopher M. Monsere, Todd Johnson, Karen Dixon, Jianfei Zheng, Ida Schalkwyk
TREC Final Reports
This report summarizes the results of an analysis of the safety performance of Oregon’s intersections. Following a pilot study, a database of 500 intersections randomly sampled from around the state of Oregon in both urban and rural environments was assembled. These intersections were categorized into eight types based on number of legs (3 and 4), land use (urban or rural) and traffic control (signalized or minor stop-control). These categories were chosen to align with the intersection types in AASHTO’s recently released Highway Safety Manual (HSM). Geometric and traffic control elements were supplemented by compiling crash data and volumes on the …
Resizable, Scalable, Concurrent Hash Tables Via Relativistic Programming, Josh Triplett, Paul E. Mckenney, Jonathan Walpole
Resizable, Scalable, Concurrent Hash Tables Via Relativistic Programming, Josh Triplett, Paul E. Mckenney, Jonathan Walpole
Computer Science Faculty Publications and Presentations
Presentation focusing on software synchronization, thread locking, transactional memory, and relativistic programming. Hash table algorithms are presented with examples of relativistic list insertion and removal, and related data structures. Existing approaches are compared to new methodologies and future work with relativistic data structures.
Resizable, Scalable, Concurrent Hash Tables, Josh Triplett, Paul E. Mckenney, Jonathan Walpole
Resizable, Scalable, Concurrent Hash Tables, Josh Triplett, Paul E. Mckenney, Jonathan Walpole
Computer Science Faculty Publications and Presentations
We present algorithms for shrinking and expanding a hash table while allowing concurrent, wait-free, linearly scalable lookups. These resize algorithms allow the hash table to maintain constant-time performance as the number of entries grows, and reclaim memory as the number of entries decreases, without delaying or disrupting readers.
We implemented our algorithms in the Linux kernel, to test their performance and scalability. Benchmarks show lookup scalability improved 125x over readerwriter locking, and 56% over the current state-of-the-art for Linux, with no performance degradation for lookups during a resize.
To achieve this performance, this hash table implementation uses a new concurrent …
Redesign Of Freshman Electrical Engineering Courses For Improved Motivation And Early Introduction Of Design, Phillip Wong, Melinda Holtzman, Branimir Pejcinovic, Malgorzata Chrzanowska-Jeske
Redesign Of Freshman Electrical Engineering Courses For Improved Motivation And Early Introduction Of Design, Phillip Wong, Melinda Holtzman, Branimir Pejcinovic, Malgorzata Chrzanowska-Jeske
Electrical and Computer Engineering Faculty Publications and Presentations
The student experience during the freshman year has been recognized as one of the keys to not only attracting more students into engineering and improving retention, but also to forming some significant attributes of successful engineering graduates. Portland State University is an urban university, and its Electrical and Computer Engineering (ECE) department serves a relatively large and very diverse student population including a large fraction of transfer and part-time students. Traditionally, all engineering disciplines within our Maseeh College of Engineering and Computer Science had a similar freshman year curriculum. The common entry course – Engineering and Applied Science (EAS) 101 …
Factors For Improved Fish Passage Waterway Construction, David N. Sillars, Hamid Moradkhani, Nicholas Tymvios, Trevor D. Smith
Factors For Improved Fish Passage Waterway Construction, David N. Sillars, Hamid Moradkhani, Nicholas Tymvios, Trevor D. Smith
TREC Final Reports
Streambeds are important fish passageways in Oregon; they provide for the necessary habitats and spawning cycles of a healthy fish population. Oregon state law requires that hydraulic structures located in water properly provide fish passage. Increasingly stringent state and federal regulations apply to these fish passageways, and designers must become more cognizant of conditions over a range of flows to accommodate fish movement and avoid expensive structural failure of these passageways. Fish passage structures are built when roads cross streambeds and may include culverts, or bridges. When these structures are built, the streambeds are re-created using a technique called “roughened …
Efficient Support Of Consistent Cyclic Search With Read-Copy-Update And Parallel Updates, Jonathan Walpole, Paul E. Mckenney
Efficient Support Of Consistent Cyclic Search With Read-Copy-Update And Parallel Updates, Jonathan Walpole, Paul E. Mckenney
Computer Science Faculty Publications and Presentations
A method, system and computer program product for supporting concurrent updates to a shared data element group while preserving group integrity on behalf of one or more readers that are concurrently referencing group data elements without using locks or atomic instructions. Two or more updaters may be invoked to generate new group data elements. Each new data element created by the same up dater is assigned a new generation number that is different than a global generation number associated with the data element group and which allows a reader of the data element group to determine whether the new data …
Systems Ideas For The Scientific And Societal Imperatives Of The Coastal Ocean: Case Of The Bp Oil Gusher In The Gulf Of Mexico, Spring & Summer 2010, Christopher Mooers
Systems Ideas For The Scientific And Societal Imperatives Of The Coastal Ocean: Case Of The Bp Oil Gusher In The Gulf Of Mexico, Spring & Summer 2010, Christopher Mooers
Systems Science Friday Noon Seminar Series
In recent decades, great progress has been made in advancing the scientific understanding of the coastal ocean (i.e., the 200 nautical mile Exclusive Economic Zone (EEZ)) across a broad set of disciplines. Simultaneously, the societal use of the coastal ocean has skyrocketed through, for example, increased shipping & boating, sports & commercial fishing, and exploitation of non-living resources, such as, oil & gas extraction and sand & gravel mining. International law and national policy assign coastal nations the responsibility for stewardship (i.e., wise management) of their respective EEZs. The scope of the stewardship and applications can be summarized as (1) …
Terahertz Material Detection From Diffuse Surface Scattering, Scott Schecklman, Lisa M. Zurk, Samuel C. Henry, Gabriel Paul Kniffin
Terahertz Material Detection From Diffuse Surface Scattering, Scott Schecklman, Lisa M. Zurk, Samuel C. Henry, Gabriel Paul Kniffin
Electrical and Computer Engineering Faculty Publications and Presentations
The potential for terahertz (THz) spectroscopy to detect explosives and other materials of interest is complicated by rough surface scattering. Our previous work has demonstrated that by averaging over diffuse observation angles and surfaces, spectral features could be recovered from laboratory measurements and numerical computer simulations. In addition to averaging, a low-pass cepstrum filter was used to reduce noise due to the random rough surface. This paper expands on these concepts by using the cepstrum of both the random rough surface and the material properties of the target material to choose an optimal cutoff frequency for the filter. The utility …
A Relativistic Enhancement To Software Transactional Memory, Philip William Howard, Jonathan Walpole
A Relativistic Enhancement To Software Transactional Memory, Philip William Howard, Jonathan Walpole
Computer Science Faculty Publications and Presentations
Relativistic Programming is a technique that allows low overhead, linearly-scalable concurrent reads. It also allows joint access parallelism between readers and a writer. Unfortunately, it has so far been limited to a single writer so it does not scale on the write side. Software Transactional Memory (STM) is a technique that allows programs to take advantage of disjoint access parallelism on both the read-side and write-side. Unfortunately, STM systems have a higher overhead than many other synchronization mechanisms so although STM scales, STM starts from a lower baseline. We propose combining relativistic programming and software transactional memory in a way …
Biokinetic Mechanisms Linked With Musculoskeletal Health Disparities: Stochastic Models Applying Tikhonov's Theorem To Biomolecule Homeostasis., Asit K. Saha, Yu Liang, Sean S. Kohles
Biokinetic Mechanisms Linked With Musculoskeletal Health Disparities: Stochastic Models Applying Tikhonov's Theorem To Biomolecule Homeostasis., Asit K. Saha, Yu Liang, Sean S. Kohles
Mechanical and Materials Engineering Faculty Publications and Presentations
Multiscale technology and advanced mathematical models have been developed to control and characterize physicochemical interactions, respectively, enhancing cellular and molecular engineering progress. Ongoing tissue engineering development studies have provided experimental input for biokinetic models examining the influence of static or dynamic mechanical stimuli (Saha, A. K., and Kohles, S. S., 2010, “A Distinct Catabolic to Anabolic Threshold Due to Single-Cell Nanomechanical Stimulation in a Cartilage Biokinetics Model,” J. Nanotechnol. Eng. Med., 1(3) p. 031005; 2010, “Periodic Nanomechanical Stimulation in a Biokinetics Model Identifying Anabolic and Catabolic Pathways Associated With Cartilage Matrix Homeostasis,” J. Nanotechnol. Eng. Med., 1(4), p. 041001). In …
Statistical Comparisons Of Watershed-Scale Response To Climate Change In Selected Basins Across The United States, John Risley, Hamid Moradkhani, Lauren Hay, Steve Markstrom
Statistical Comparisons Of Watershed-Scale Response To Climate Change In Selected Basins Across The United States, John Risley, Hamid Moradkhani, Lauren Hay, Steve Markstrom
Civil and Environmental Engineering Faculty Publications and Presentations
In an earlier global climate-change study, air temperature and precipitation data for the entire twenty-first century simulated from five general circulation models were used as input to precalibrated watershed models for 14 selected basins across the United States. Simulated daily streamflow and energy output from the watershed models were used to compute a range of statistics. With a side-by-side comparison of the statistical analyses for the 14 basins, regional climatic and hydrologic trends over the twenty-first century could be qualitatively identified. Low-flow statistics (95% exceedance, 7-day mean annual minimum, and summer mean monthly streamflow) decreased for almost all basins. Annual …
Quantum Phase Estimation Using Multivalued Logic, Marek Perkowski, Vamsi Parasa
Quantum Phase Estimation Using Multivalued Logic, Marek Perkowski, Vamsi Parasa
Electrical and Computer Engineering Faculty Publications and Presentations
We generalize the Quantum Phase Estimation algorithm to MVL logic. We show the quantum circuits for QPE using qudits. We derive the performance requirements of the QPE to achieve high probability of success. We show how this leads to logarithmic decrease in the number of qudits and exponential decrease in error probability of the QPE algorithm as the value of the radix d increases.
Synthesis Of Reversible Synchronous Counters, Marek Perkowski, Mozammel H.A. Khan
Synthesis Of Reversible Synchronous Counters, Marek Perkowski, Mozammel H.A. Khan
Electrical and Computer Engineering Faculty Publications and Presentations
In this paper, we concentrate on design of synchronous counters directly from reversible gates.
Improved Complexity Of Quantum Oracles For Ternary Grover Algorithm For Graph Coloring, Marek Perkowski, Yushi Wang
Improved Complexity Of Quantum Oracles For Ternary Grover Algorithm For Graph Coloring, Marek Perkowski, Yushi Wang
Electrical and Computer Engineering Faculty Publications and Presentations
The Graph Coloring Grover Algorithm has several applications in logic synthesis, scheduling, allocation, planning, robot motion, robot communication, resource allocation, conflict resolution, floor-planning, and many others.
It can serve as a “generic CSP solver” similar to a general SAT solver.
Research On Coupled Human And Natural Systems (Chans): Approach, Challenges, And Strategies, Marina Alberti, Heidi Asbjornsen, Lawrence A. Baker, Nicholas Brozović, Laurie E. Drinkwater, Scott A. Drzyzga, Claire A. Jantz, José Fragoso, Daniel S. Holland, Timothy A. Kohler, Jianguo Liu, William J. Mcconnell, Herbert D. G. Maschner, James D. A. Millington, Michael Monticino, Guillermo Podestá, Robert Gilmore Pontius Jr., Charles L. Redman, Nicholas J. Reo, David J. Sailor, Gerald Urquhart
Research On Coupled Human And Natural Systems (Chans): Approach, Challenges, And Strategies, Marina Alberti, Heidi Asbjornsen, Lawrence A. Baker, Nicholas Brozović, Laurie E. Drinkwater, Scott A. Drzyzga, Claire A. Jantz, José Fragoso, Daniel S. Holland, Timothy A. Kohler, Jianguo Liu, William J. Mcconnell, Herbert D. G. Maschner, James D. A. Millington, Michael Monticino, Guillermo Podestá, Robert Gilmore Pontius Jr., Charles L. Redman, Nicholas J. Reo, David J. Sailor, Gerald Urquhart
Mechanical and Materials Engineering Faculty Publications and Presentations
Understanding the complexity of human–nature interactions is central to the quest for both human well-being and global sustainability. To build an understanding of these interactions, scientists, planners, resource managers, policy makers, and communities increasingly are collaborating across wide-ranging disciplines and knowledge domains. Scientists and others are generating new integrated knowledge on top of their requisite specialized knowledge to understand complex systems in order to solve pressing environmental and social problems (e.g., Carpenter et al. 2009). One approach to this sort of integration, bringing together detailed knowledge of various disciplines (e.g., social, economic, biological, and geophysical), has become known as the …
Synthesis Of Quantum Circuits In Linear Nearest Neighbor Model Using Positive Davio Lattices, Marek Perkowski, Martin Lukac, Dipal Shah, Michitaka Kameyama
Synthesis Of Quantum Circuits In Linear Nearest Neighbor Model Using Positive Davio Lattices, Marek Perkowski, Martin Lukac, Dipal Shah, Michitaka Kameyama
Electrical and Computer Engineering Faculty Publications and Presentations
We present a logic synthesis method based on lattices that realize quantum arrays in One-Dimensional Ion Trap technology. This means that all gates are built from 2x2 quantum primitives that are located only on neighbor qubits in a onedimensional space (called also vector of qubits or Linear Nearest Neighbor (LNN) architecture). The Logic circuits designed by the proposed method are realized only with 3*3 Toffoli, Feynman and NOT quantum gates and the usage of the commonly used multi-input Toffoli gates is avoided. This realization method of quantum circuits is different from most of reversible circuits synthesis methods from the literature …
Modal Logic And Its Applications, Explained Using Puzzles And Examples, Marek Perkowski
Modal Logic And Its Applications, Explained Using Puzzles And Examples, Marek Perkowski
Electrical and Computer Engineering Faculty Publications and Presentations
1.We shall be concerned, at first, with alethicmodal logic, or modal logic tout court. 2.The starting point, once again, is Aristotle, who was the first to study the relationship between modal statements and their validity. 3.However, the great discussion it enjoyed in the Middle Ages. 4.The official birth date of modal logic is 1921, when Clarence Irving Lewis wrote a famous essay on implication.
Scalable Correct Memory Ordering Via Relativistic Programming, Josh Triplett, Philip William Howard, Paul E. Mckenney, Jonathan Walpole
Scalable Correct Memory Ordering Via Relativistic Programming, Josh Triplett, Philip William Howard, Paul E. Mckenney, Jonathan Walpole
Computer Science Faculty Publications and Presentations
We propose and document a new concurrent programming model, relativistic programming. This model allows readers to run concurrently with writers, without blocking or using expensive synchronization. Relativistic programming builds on existing synchronization primitives that allow writers to wait for current readers to finish with minimal reader overhead. Our methodology models data structures as graphs, and reader algorithms as traversals of these graphs; from this foundation we show how writers can implement arbitrarily strong ordering guarantees for the visibility of their writes, up to and including total ordering.
Generalized Construction Of Scalable Concurrent Data Structures Via Relativistic Programming, Josh Triplett, Paul E. Mckenney, Philip W. Howard, Jonathan Walpole
Generalized Construction Of Scalable Concurrent Data Structures Via Relativistic Programming, Josh Triplett, Paul E. Mckenney, Philip W. Howard, Jonathan Walpole
Computer Science Faculty Publications and Presentations
We present relativistic programming, a concurrent programming model based on shared addressing, which supports efficient, scalable operation on either uniform shared-memory or distributed shared- memory systems. Relativistic programming provides a strong causal ordering property, allowing a series of read operations to appear as an atomic transaction that occurs entirely between two ordered write operations. This preserves the simple immutable-memory programming model available via mutual exclusion or transactional memory. Furthermore, relativistic programming provides joint-access parallelism, allowing readers to run concurrently with a writer on the same data. We demonstrate a generalized construction technique for concurrent data structures based on relativistic programming, …
Case Study Evaluation Of Dynamic Traffic Assignment Tools, John Gliebe, Åsa Bergman
Case Study Evaluation Of Dynamic Traffic Assignment Tools, John Gliebe, Åsa Bergman
Urban Studies and Planning Faculty Publications and Presentations
A case study was undertaken in order to evaluate the potential use of dynamic traffic assignment (DTA) tools by Oregon Department of Transportation (ODOT) and its partner agencies. The objectives of this study were to provide insight into the nature of DTA models, to inform the program selection process, and to develop realistic expectations for potential DTA work plans. The overarching goal of this report is to describe the process followed and experiences of the study team in developing and testing DTA network models. Two available DTA programs were selected for in-depth analysis from a preliminary screening of available programs: …
Assessment And Refinement Of Real-Time Travel Time Algorithms For Use In Practice, Phase Ii, Kristin A. Tufte, Soyoung Ahn, Sirisha Murthy Kothuri
Assessment And Refinement Of Real-Time Travel Time Algorithms For Use In Practice, Phase Ii, Kristin A. Tufte, Soyoung Ahn, Sirisha Murthy Kothuri
TREC Final Reports
The Federal Highway Administration (FHWA) has put a high priority on the use of existing dynamic message signs (DMS) to provide travel time estimates to the public. The Oregon Department of Transportation (ODOT) has three DMS in the Portland metropolitan area configured to display travel time information. In the near future, ODOT would like to make travel time estimates available on additional DMS, over the Internet on tripcheck.com and via 511. Travel time estimates are valuable to the traveling public; however, the estimates must be accurate to be useful. The purpose of this study is to extend prior travel time …