Weaving sections are common design elements on freeway facilities such as near ramps and freeway to-freeway connectors. When the traffic demands exceed the capacity at weaving areas congestion may occur, which affects the operation of the entire freeway section. Traffic operational problems also may exist at weaving areas even when traffic demands are less than capacity because of the complexity of vehicle interactions, resulting in poor level of service (LOS) and potential safety problems. Existing procedures for the design and analysis of freeway weaving sections have several shortcomings, and their practical application often produces inconsistent results.

This report describes the work performed under PATH Task Order 6304. The objective of the study was to evaluate the existing weaving analysis procedures to determine under which conditions the “best available” tools are most effective. The HCM2000, Leisch and Level D methods were evaluated using field data from 36 weaving sections for a total of 189 data points of speeds and volumes. A weaving performance matrix was developed to assist in determining which method to be used for a given mix of design and operational characteristics in a weaving section.

The Airspace Flow Program (AFP) is a traffic management initiative that aims to mitigate delays arising from en route capacity constraints, by holding flights on the ground and metering their flow through constrained regions. It has been successful in controlling traffic with reasonable delays, but the procedures must be improved upon to handle future projected demands. This dissertation explores a future AFP concept that incorporates structured user preference inputs in a centrally-managed assignment of ground delays as well as reroutes. However, the commercial aviation industry is very competitive, and airlines are reticent to share detailed operational information without clear benefits in return. This idea must be taken into consideration when designing flight resource assignment strategies, as we address a very fundamental question in transportation service provision: how does a central authority allocate resources efficiently when they are uncertain about what users want?

A modeling framework was developed to evaluate and compare allocation strategies, under differing assumptions regarding the information that traffic managers may (or may not) have about airline flight costs. We introduce several resource allocation strategies that feature different allocation rules and route preference inputs requested of flight operators. We assess the total user-cost impact of each allocation strategy through a simple generalized cost function that represents the cost of delay for each flight caught in the AFP. This flight cost function consists of two parts: the first is a simple representation of operator flight cost characteristics that the traffic managers have adopted, while the second consists of a flight's routing preferences that are not captured by the first, and therefore are privately known to each flight's operator but not to traffic managers unless the information is offered. In one allocation strategy, users are asked to provide their private information in exchange for the employment of a resource allocation rule that rewards flights for early submission. In another, users are not asked to provide their proprietary information but are not offered the same "guarantee" regarding resource allocations, i.e. flights have less idea about what resources they will receive in the allocation. We identify some basic properties about the relationships of the assignment schemes' total flight cost efficiency results, under changing assumptions about the quality of the central decision maker's knowledge about the flight operators' route preferences. Numerical examples illustrate situations where sacrificing a system-optimal allocation rule for a sequential one (First Submitted, First Assigned, or FSFA), in order to obtain and utilize flight operators' private information about route preferences, will result in more user cost efficient resource allocations. The examples also illustrate situations where the opposite is true, i.e. it is more efficient to use a system-optimal allocation without private route preference information. Also it is found that the existing Ration-by-Schedule algorithm performs poorly in the context of our modeling framework.

The above results do not consider the effects of gaming behavior. As a result, we also study the gaming and truth-telling behavior of flight operators in response to the competition for limited en route resources. It is demonstrated that operators are incentivized to provide untruthfully high inputs in schemes where a system-optimal allocation rule is used. Using a gaming analysis, it is also demonstrated that the operators' equilibrium submission strategies in the FSFA scheme can vary significantly depending on the conditions of the AFP and their private information. However, it is also shown that flights are highly incentivized to submit at the very beginning of the FSFA planning period, which is favorable for air traffic flow management (ATFM) planning and coordination.

This dissertation presents a history of the development of abstract art in the 1920s and 1930s, the period of its expansion and consolidation as an identifiable movement and practice of art. I argue that the emergence of the category of abstract art in the 1920s is grounded in a voluntaristic impulse to remake the world. I argue that the consolidation of abstract art as a movement emerged out of the Parisian reception of a new Soviet art practice that contained a political impetus that was subsequently obscured as this moment passed. The occultation of this historical context laid the groundwork for the postwar “multiplication” of the meanings of abstraction, and the later tendency to associate its early programmatic aspirations with a more apolitical mysticism.

Abstraction has a long and varied history as both a conceptual-aesthetic practice and as an ideal. In the first chapter, I provide a conceptual overview of the terms used by abstract artists and their contemporaries, as well as provide a historicization of the meaning of pure abstraction in terms of the relationship of modernism to its own eighteenth century beginnings and antiquity. The second chapter focuses on the “Soviet moment” of pure abstraction by looking at the Soviet contributions—primarily Konstantin Melnikov’s pavilion—to the 1925 Exposition International des Arts Décoratifs et Modernes in Paris and their enthusiastic reception. The third chapter continues the examination of pure abstraction but in the context of the Parisian art world. It begins with an examination of the L’Art d’Au’jourd’hui exhibit of December 1925 and the two paintings Mondrian contributed to it. I seek to demonstrate that while Mondrian’s practice cannot be assimilated to the revolutionary aesthetics of the previous chapter, it was, nevertheless fundamentally connected to a certain vision of capitalism as a problem of everyday life. I argue that it is within the historical context of a dialectic between a “Soviet moment” and a Parisian experience of daily life that the rise and fall of pure abstraction should be understood. In the final chapter, I present the work of Jean Hélion, a young, committed French painter, whose trajectory from geometric to figural abstraction provides an understanding of the aesthetic and political impasses, as well as defeats, of the period, a case that casts an unsettling light on the entire adventure of pure abstraction.

As part of the California PATH program, the Paramics microscopic traffic simulation model was evaluated through a pilot application to the I-680 freeway corridor, one of the most highly congested facilities in the San Francisco Bay Area. The main objective of the project was to test the capability of the model to serve as a tool for evaluating alternative transportation planning and traffic management scenarios. HOV lanes were investigated first on a "simple" network, and later on the existing I-680 corridor. An Application Programming Interface (API) "plugin" designed by Quadstone, which influences driver behavior regarding HOV lane use, was utilized in an attempt to improve HOV lane simulation. From the existing freeway model to the freeway with an HOV lane, it was found that the total vehicle hours traveled decreased 28 percent and the overall average speed increased 40 percent. Several scenarios were also developed within the I-680 Paramics model as part of a sensitivity analysis, to assess the effects on the network of altering certain input parameters. Ramp metering was later tested on the calibrated network with the added HOV lane, using various supporting API modules for Paramics developed at PATH. The local actuated ramp control strategy Alinea was implemented and evaluated. It should be noted that Caltrans does not plan to implement the Alinea strategy as tested in the simulation. The report describes the approach used to fine-tune the control strategy, then presents and discusses the results that were obtained. It was found that the overall system performance did not improve after the implementation of ramp control, because the benefits on the mainline freeway did not outweigh the additional delays experienced on the on-ramps. The report identifies a number of factors that may explain why the benefits of ramp metering could have been underestimated in this particular study. The Paramics model, together with its supporting modules, was found to be an effective and reliable tool for modeling traffic operations on a large-scale and highly congested freeway corridor. It can be used to evaluate the impact of an HOV lane or investigate ramp control metering strategies, and to undertake sensitivity analyses for the various alternative scenarios in a timely and effective way. However, a number of limitations and shortcomings have been identified, contributing to a likely underestimation of the ramp metering benefits in this study. The most important factor is the absence of route diversion. Because no parallel surface street was modeled, the model did not capture the spatial diversion that is likely to occur when ramp metering is implemented. Another key issue is the ramp queue control process embedded in the Alinea control strategy: because of high demand levels on many on-ramps, the storage capacity is often reached during the simulation period, resulting in an override of the Alinea-optimized metering rate. This phenomenon prevents ramp control to reach the full potential of mainline freeway improvements. Finally, no modal response was considered in the scenario comparisons, which may have contributed to improving the overall system performance with a higher usage of HOV bypass and mainline lanes. These limitations will be addressed in future applications of Paramics to other Bay Area freeways.

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