Master of Science

The Manual on Uniform Traffic Control Devices (MUTCD) establishes the basic principles for the design, selection, installation, operation, maintenance, and removal of traffic control devices (TCDs). The MUTCD indicates that some TCDs that are required and some are recommended, depending on the situation. However, most TCDs are not required and the decision to use a given TCD in a given situation is typically made by an engineer (or an individual working under engineering supervision) based on a variety of information. Not all engineers have the same degree of experience in making TCD decisions, and not all engineers that make these decisions have traffic engineering expertise. There are many other factors not addressed by the MUTCD that can lead to differences in the decision-making process. To assist engineers with evaluating these factors, this research developed a decision analysis process to assist engineers with making TCD decisions. The value of this research is the idea that the decision analysis process for TCD can be modeled and analyzed using appropriate factors. The developed factors include need, impact, influence, and cost. The process developed in this research applies two elements to each factor. One element compares the importance of each factor among all the other factors, and the other incorporates the engineer's judgment into the TCD decision. The first element described uses a decision analysis method, analytic hierarchy process, to determine the weights for each factor, or coefficients, as applied generally to a TCD. The second uses a mixture of quantitative and qualitative engineering judgment to determine the degree to which the factor applies to the TCD situation, or situational variable. The output of this process was a utility value that can be compared to a scale and determine the installation value of the device. This process will contribute to more uniform decisions amongst all levels of experience in TCD decision-making. Additional research that could expand on this developed process would include data collection on typical importance values for each factor as applied to a TCD and on decision scales for specific TCD situations. When applying this research, it is important to remember that it is not the intent of this process to remove engineering judgment. This is an important part of the process and should remain as such.

Air traffic demand is growing. New methods of airspace design are required that can enable new designs, do not depend on current operations, and can also support quantifiable performance goals. The main goal of this thesis is to develop methods to model inherent safety and control cost so that these can be included as principal objectives of airspace design, in support of prior work which examines capacity. The first contribution of the thesis is to demonstrate two applications of airspace analysis and design: assessing the inherent safety and control cost of the airspace. Two results are shown, a model which estimates control cost depending on autonomy allocation and traffic volume, and the characterization of inherent safety conditions which prevent unsafe trajectories. The effects of autonomy ratio and traffic volume on control cost emerge from a Monte Carlo simulation of air traffic in an airspace sector. A maximum likelihood estimation identifies the Poisson process to be the best stochastic model for control cost. Recommendations are made to support control-cost-centered airspace design. A novel method to reliably generate collision avoidance advisories, in piloted simulations, by the widely-used Traffic Alert and Collision Avoidance System (TCAS) is used to construct unsafe trajectory clusters. Results show that the inherent safety of routes can be characterized, determined, and predicted by relatively simple convex polyhedra (albeit multi-dimensional and involving spatial and kinematic information). Results also provide direct trade-off relations between spatial and kinematic constraints on route geometries that preserve safety. Accounting for these clusters thus supports safety-centered airspace design. The second contribution of the thesis is a general methodology that generalizes unifying principles from these two demonstrations. The proposed methodology has three steps: aggregate data, synthesize lean model, and guide design. The use of lean models is a result of a natural flowdown from the airspace view to the requirements. The scope of the lean model is situated at a level of granularity that identifies the macroscopic effects of operational changes on the strategic level. The lean model technique maps low-level changes to high-level properties and provides predictive results. The use of lean models allows the mapping of design variables (route geometry, autonomy allocation) to design evaluation metrics (inherent safety, control cost).

Prepared for NASA-Ames Research Center. Grant NSG-2180. / Description based on: Sept. 1978/Mar. 1979. Subtitle varies slightly: Semi-annual status report. Principal investigators: 1978/79- Michael Athans, Mark E. Connelly.

Modern network interface controllers allow the host to offload packet processing to hardware in order to improve performance. At the present time, the advanced features are utilized in the Linux kernel by offloading the Traffic Control subsystem. Since this subsystem has been designed for a completely different purpose, its usage for hardware offloading is impractical and unreliable. Furthermore, in its current state the subsystem is not capable of utilizing all hardware features, which are often poorly documented. The presented work adopts a different approach to the problem. Five high-end controllers and their packet-processing pipelines were examined in detail. Accounting for their projected future development, common traits and features were identified. The researched information was used to draft a proposal for a new Linux subsystem, more compatible with hardware offloading than the current solution. The proposed subsystem defines a sufficiently descriptive interface to utilize the majority of hardware-offloaded features while avoiding common problems caused by excessively generalized approach of Traffic Control.

No description available.

Generic airspace, or air traffic control sectors with similar operational characteristics, is an operational concept being proposed as a means of increasing staffing flexibility and reducing training times as part of the Federal Aviation Administration’s (FAA’s) Next Generation (NextGen) air traffic control (ATC) modernization efforts. A key need for implementing generic airspace is identifying groups of similar sectors with respect to training required for controllers to make transitions between those sectors. Through the development and validation process of the studies performed in this thesis, a structure-based classification scheme was found to be an effective way to classify sectors in order to support a minimal differences training approach to generic airspace. The resulting classes of sectors are expected to have fewer transition barriers and support increased staffing flexibility. In order to assess similarities of airspace sectors, factors affecting how easily a controller makes a transition from one sector to another were identified using semi-structured interviews with experienced air traffic controllers. The most important factors appear to reflect familiarity with types of operations and common traffic patterns, providing a basis for classifying groups of sectors. The controllers identified some techniques that are easily transferable as well. Some factors that are very specific to transitions were identified as well, such as “knowing the neighbor sectors” and “coastal area” factors. Based on the most important factors, traffic patterns in 404 high-altitude National Airspace System (NAS) sectors were examined for common traffic patterns. These traffic patterns were used as the basis for two classification approaches, a holistic classification approach and a decompositional classification approach. These approaches are used to classify current air traffic control sectors into classes with common structural characteristics. The results identify existing sectors with near-term potential as being generic sectors that support a minimal differences training approach to generic airspace. Further analysis with the sector classification results identified that the number of factors incorporated in the classification methods are directly associated with the method's effectiveness. In order to examine the validity of the developed classification methods and to assess the relative importance of the factors involving transitions identified by the interviews, an online survey was conducted with 56 air traffic controllers. The results indicated that the classification methods developed support controllers' perception of airspace similarities. Some qualitative data gained from the survey provides an insightful aspect for future steps continuing this study such as additional important factors to be considered. Some of these factors are considered as part of the classification schemes developed in this thesis while some are yet to be incorporated. Some of these additional factors were found to be more feasible to be incorporated into future classification schemes than other factors.

Generic airspace, or air traffic control sectors with similar operational characteristics, is an operational concept being proposed as a means of increasing staffing flexibility and reducing training times as part of the Federal Aviation Administration’s (FAA’s) Next Generation (NextGen) air traffic control (ATC) modernization efforts. A key need for implementing generic airspace is identifying groups of similar sectors with respect to training required for controllers to make transitions between those sectors. Through the development and validation process of the studies performed in this thesis, a structure-based classification scheme was found to be an effective way to classify sectors in order to support a minimal differences training approach to generic airspace. The resulting classes of sectors are expected to have fewer transition barriers and support increased staffing flexibility. In order to assess similarities of airspace sectors, factors affecting how easily a controller makes a transition from one sector to another were identified using semi-structured interviews with experienced air traffic controllers. The most important factors appear to reflect familiarity with types of operations and common traffic patterns, providing a basis for classifying groups of sectors. The controllers identified some techniques that are easily transferable as well. Some factors that are very specific to transitions were identified as well, such as “knowing the neighbor sectors” and “coastal area” factors. Based on the most important factors, traffic patterns in 404 high-altitude National Airspace System (NAS) sectors were examined for common traffic patterns. These traffic patterns were used as the basis for two classification approaches, a holistic classification approach and a decompositional classification approach. These approaches are used to classify current air traffic control sectors into classes with common structural characteristics. The results identify existing sectors with near-term potential as being generic sectors that support a minimal differences training approach to generic airspace. Further analysis with the sector classification results identified that the number of factors incorporated in the classification methods are directly associated with the method's effectiveness. In order to examine the validity of the developed classification methods and to assess the relative importance of the factors involving transitions identified by the interviews, an online survey was conducted with 56 air traffic controllers. The results indicated that the classification methods developed support controllers' perception of airspace similarities. Some qualitative data gained from the survey provides an insightful aspect for future steps continuing this study such as additional important factors to be considered. Some of these factors are considered as part of the classification schemes developed in this thesis while some are yet to be incorporated. Some of these additional factors were found to be more feasible to be incorporated into future classification schemes than other factors.

Communication applications have diverse network service requirements. For instance, <em>Voice over IP</em> (VoIP) demands short end-to-end delay, whereas <em>File Transfer Protocol</em> (FTP) benefits more from high throughput than short delay. However, the Internet delivers a uniform best-effort service. As a result, much research has been conducted to enhance the Internet to provide service differentiation. Most of the existing proposals require additional access-control mechanisms, such as admission control and pricing, which are complicated to implement and render these proposals not incrementally deployable. <em>Incentive-compatible Differentiated Scheduling</em> (ICDS) provides incentives for applications to choose a service class according to their burst characteristics without additional access-control mechanisms. <br /><br /> This thesis investigates the behaviour of ICDS with different types of traffic by analysis and extensive simulations. The results show some evidences that ICDS can achieve its design goal. In addition, this thesis revises the initial ICDS algorithm to provide fast convergence for TCP traffic.

No description available.