Captivity to a choice is an aspect of the choice process that is not well understood in the transportation area. The current context of understanding of this phenomenon is superficial and covers only being physically constrained to a single choice. However, there are many related concepts and behavioral phenomena, as discussed in various other fields, such as brand or service loyalty, brand switching, resistance to change, and habit formation, that can contribute to the formation of some degree of captivity. Furthermore, a deeper understanding of these phenomena is becoming important to the transportation industry because of high levels of competition. For instance, it has become important for airline companies to develop customer loyalty to survive in the industry, after the airline industry in the United States was deregulated in 1978. The main aim of this work, therefore, is to develop a broad framework for describing the fundamentals of captivity, i.e., what, how, and when the underlying processes bring about captivity, and to form a theoretical basis for it. After presenting a framework within which captivity can be described, a way of handling it through “stated choices” is tested by means of a modeling effort using intercity travel mode choice data from Saudi Arabia. The travel mode choice models calibrated for two trip purposes indicate the feasibility of this method. Finally, conclusions and the areas that need further research are presented.

The estimation of vehicle kilometers of travel at various levels of a road network is one of the key tasks of any road and transport authority. This paper introduces a method to estimate the vehicle kilometers of travel. Stratified probability proportional to size (PPS) cluster sampling has been applied as a developmental tool in the kingdom of Morocco. The PPS sampling is based on classical statistical theory. Using the PPS sampling together with stratified sampling, it is possible to optimally allocate counting resources so that an acceptable level of reliability can be obtained in different parts of the network. In addition, the costs of countings may be included as part of the optimization. The PPS method requires some historical data to weigh different clusters of the road network according to their importance. However, mechanical approaches based on statistical theory alone do not result in satisfactory solutions, but the counting system should also be evaluated taking into account technical, economical, and organizational factors.

Travel time is currently believed to be one of the best, if not the best, indicators of the quality of flow and operation on a transportation facility. Travel time is such a good measure because it is easy for both commuters and transportation engineers to understand. The problem with travel time, however, is that there currently does not exist a method that is capable of collecting this measurement automatically, in real-time, and without statistical bias. These elements should certainly be considered as basic requirements for traffic management centers as they progress to meet the future demands of Intelligent Transportation Systems applications. A new technology for measuring travel time is being tested and evaluated by researchers at the University of Washington. This new technology is a video image detection system based on vehicle tracking, called the Mobilizer. This system offers the promise of being able to track individual vehicles passively, and in real-time, along any route monitored by video cameras. This system also provides all of the standard traffic measures reported by previous generation point processing video image systems, but is also capable of reporting link travel times, which cannot be measured directly by the point processing systems. This paper presents the preliminary findings of the Mobilizer system based on results from studies performed at local roadway segments within the Puget Sound region. These preliminary results indicate that the Mobilizer is capable of matching vehicles in successive fields-of-view with a reasonable degree of accuracy and that the travel time estimates provided by the system are statistically valid.

Highway pavement maintenance is very expensive not only in terms of costs to the responsible agencies, but also in terms of disruptive delays to users. Construction and maintenance activities on two-lane, two-way highways often require the closure of one travel lane. Longer work zones and the longer cycle times associated with such zones tend to increase the user delay costs. Maintenance work can be performed more efficiently, i.e., with fewer repeated setups, in longer zones. A mathematical model is developed to optimize the work zone length and traffic control on two-lane, two-way highways where one lane at a time is closed. The objective is to minimize the total cost, including the agency cost and user delay cost. Unbalanced traffic flows in both directions are considered. The optimized variables (e.g., work zone length and cycle time) and the sensitivity results generated from a numerical example are presented in this study.

One of the primary difficulties in completing evaluations of real-time adaptive traffic signal systems has been the lack of effective modeling tools to perform controlled and repeatable analytical experiments. Recently, a method to analyze the delay characteristics of an existing real-time adaptive traffic signal control system has been developed. The procedure has been used to evaluate the performance of the Sydney Coordinated Adaptive Traffic System (SCATS) in South Lyon, Michigan. The objective of this study was to more closely examine the relationship of major and minor street delay under the SCATS and fixed-time forms of signal control. The effect on left turn delay at critical locations was also compared to the delay change in the through traffic. The comparisons showed that SCATS control resulted in significant delay reductions to left turn traffic compared to the through movements. The improvement was especially pronounced at the major street approaches. To further address the delay effect of SCATS control in South Lyon, the relationships between volume, delay, and green time of the various traffic moments were also compared. These comparisons showed that SCATS tended to allocate more green time to left turn traffic when compared to the fixed-time system.

This paper discusses the nature of problems encountered during the integration of software that separately supports the mutually integrated processes of road design, construction, and maintenance. A road model based on the data requests of (some) software, which enables their effective linking to an integrated environment, will also be described. The architecture and structure of the elaborated software environment, based on an integrated road model, including existing as well as new software components, is also presented. In addition, this paper will describe experiences gained with application of the unified road model and its advantages and deficiencies, as well as future potential.

Recently, many public transportation agencies have begun to consider changing the way that they manage highway maintenance operations. One system under consideration, already well developed for private businesses, is performance measurement. While there are references for developing performance measures for other public services, there is nothing relevant that applies specifically to highway maintenance. This paper examines the general theories of performance measurement systems, based on current conditions and practices in the province of Alberta, Canada, and applies them to develop examples for highway maintenance. This paper concludes with a brief analysis regarding the extra considerations on a performance measurement system when private companies under contract to a public agency perform the work.

This paper introduces a universal methodology for the analysis of discretely sampled sealed bituminous road profile data. Several hundred kilometers of Victorian (Australia) road profile data are analyzed in both the frequency and the amplitude domains. Road profile spectral characteristics are shown to be independent of road roughness. However, statistical analysis of the road elevation data shows them to be highly nonstationary, non-Gaussian processes that contain transients. Transients are difficult to locate when the data are analyzed in the road profile elevation domain itself, as they often occur within the Gaussian distribution. The road profile spatial acceleration is adopted as the preferred analysis domain, as roughness variations and transient events are identified with greater reliability and accuracy. Analysis of the spatial acceleration data enables the identification of large amplitude, short duration events (transients) as they occur extremely outside the Gaussian distribution. Higher order statistics, such as skewness and kurtosis, as well as the crest factor, are also used to detect transients (see Appendix I). It is shown that the road surface elevation becomes a stationary mean process with a nonstationary root-mean square when analyzed in the spatial acceleration domain.

State Highway 6 in Brazos County, Tex., is experiencing significant changes in surface profile at several locations. The changes in surface profile were noticed within a few months after construction. They quickly became severe enough to adversely affect vehicle safety. The longitudinal distance between the peak of the undulations is usually greater than 30 m. Patching to maintain a reasonably safe surface profile has been performed at least annually since construction. Routine site investigations prior to construction did not reveal underlying soil conditions that could produce these kinds of pavement distresses that appeared relatively soon after the pavement subgrade was stabilized with lime. In this study, the area was investigated using soil suction profiles to determine the origin(s) of the pavement distresses manifested at the surface. Findings indicated the swells were not caused by lime stabilization of sulfate bearing soils but were the result of surface water flowing through deep cracks and/or permeable soil layers to highly plastic expansive clays. Researchers used soil suction profiles to analyze the problem and recommended remedial measures to reduce subsequent swelling.

To determine the impact of C-17 aircraft on unsurfaced airfields, the U.S. Army Engineer Waterways Experiment Station was asked to construct full-scale pavement section items and traffic them to failure with a fully loaded C-17 aircraft main gear assembly (six wheels). The extrapolation of existing criteria used on two and four wheel aircraft gear studies was suspect, particularly when considering the configuration of the C-17 aircraft main gear. Three strengths of surfacing material (6, 9, and 12 California Bearing Ratio) were used to evaluate the current criteria. The results of full-scale pavement trafficking indicate that current criteria should be considered appropriate for use as a tool in designing/evaluating the expected performance of unsurfaced airfields for operations of C-17 aircraft. It should be noted that surface shearing occurred in the landing/braking zone on unsurfaced airfields during flight tests in 1997. The criteria addressed in this paper does not consider the rutting caused by braking shear.

The C-17 Globemaster III aircraft was developed by McDonnell Douglas (now Boeing) with the capability of transporting equipment and cargo to small airfields with short runways and minimal ground support equipment. The introduction of the C-17 into the U.S. Air Force's inventory initiated the requirement to validate existing semiprepared (unsurfaced, aggregate-surfaced, and stabilized) airfield design and evaluation criteria for the operation of the C-17 aircraft. The U.S. Army Engineer Waterways Experiment Station was requested by the U.S. Air Force to characterize the structural capacity of selected semiprepared test sites and document each airfield's behavior under actual C-17 aircraft operations. The results of three live-flight tests indicate that the current U.S. Army Corps of Engineers unsurfaced airfield criteria does not adequately predict the behavior of unsurfaced airfields in arid or semiarid climates subjected to the braking and turning forces of a 226,800-kg (500,000-lb) aircraft. This investigation presents the results of the field tests and includes a regression model that can be used to predict the behavior of unsurfaced airfields in semiarid/arid environments under C-17 aircraft traffic.