Transportation planning applications typically calibrate models for a base year and then make forecast year projections. However, modelers rarely evaluate the accuracy of their forecasts by using past data sets to predict present conditions. This is complicated by the fact that longitudinal data sets for a geographical area exhibit data incompatibility, shifts in planning emphasis, temporal changes in travel characteristics, and added modeling complexity. In addition, if new data elements are needed for model improvement, these will not be available with the historical data set. In an effort to test the feasibility of using older planning data to predict the present, a case study area for which transportation planning data were available was selected at three points in time over a 25-year period. This facilitated comparison of longitudinal data sets, development of base year models, and subsequent testing of their performance for a forecast year application. This paper discusses the experience of creating a longitudinal data set for such testing and illustrations how one can use longitudinal data to ascertain the sustainability of model structures over time. Some simple workable approaches are illustrated; although these are more aggregate than desired, they convey how one may devise models that can function both in the base year and then, later, in the forecast year, in spite of changes in transportation and land use activity.

This paper proposes an approach to determine zonal fares for the attendees of the meetings or conventions flying from different cities to a single host city. The airline has to offer a fare low enough to win the contract and at the same time cover the costs and profit margins. A methodology is presented for consolidating the demand into different zones and selecting a representative city for each zone. A bilevel linear programming formulation is used to solve the problem. This model minimizes the cost of displacing high revenue individual passengers by utilizing the unused seats over different acceptable itineraries resulting in lower fares and higher load factors. The proposed algorithm is tested by generating fares for a real-world data set on convention demand obtained from an airline. The implementation results show an improvement of up to 50% over the fares calculated using the current techniques. Currently, most airlines compute fares by booking the total demand on a single itinerary that can result in higher fares thereby causing the loss of the contract.

Many decision-making problems in transportation system planning and management can be formulated as bilevel programming models, which are intrinsically nonconvex and hence difficult to solve for the global optimum. Therefore, successful implementations of bilevel models rely largely on the development of an efficient algorithm in handling realistic complications. In spite of various intriguing attempts that were made in solving the bilevel models, these algorithms are unfortunately either incapable of finding the global optimum or very computationally intensive and impractical for problems of a realistic size. In this paper, a genetic-algorithms-based (GAB) approach is proposed to efficiently solve these models. The performance of the algorithm is illustrated and compared with the previous sensitivity-analysis-based algorithm using numerical examples. The computation results show that the GAB approach is efficient and much simpler than previous heuristic algorithms. Furthermore, it is believed that the GAB approach can more likely achieve the global optimum based on the globality and parallelism of genetic algorithms.

This paper proposes a capacity-constrained traffic assignment model for strategic transport planning in which the steady-state user equilibrium principle is extended for road networks with residual queues. Therefore, the road-exit capacity and the queuing effects can be incorporated into the strategic transport model for traffic forecasting. The proposed model is applicable to the congested network particularly when the traffic demands exceed the capacity of the network during the peak period. An efficient solution method is proposed for solving the steady-state traffic assignment problem with residual queues. Then a simple numerical example is employed to demonstrate the application of the proposed model and solution method, while an example of a medium-sized arterial highway network in Sioux Falls, South Dakota, is used to test the applicability of the proposed solution to real problems.

This research aims to shed more light on the nature and frequency of secondary conflicts. Data for 15 unsignalized intersections located in Amman, Jordan, were collected by the use of a video camera. It was concluded that conflict types and grades are correlated significantly with their corresponding secondary conflict types and grades. Also, conflicts are more closely correlated with their secondary conflicts for through-cross movements, rather than for same-direction movements. Secondary conflicts of a particular grade and type may result from any conflict grade and type. It was found that for every 100 conflicts, approximately 14 secondary conflicts resulted. Moreover, same-direction secondary conflicts (C1–C4) together with through-cross secondary conflicts (C8 and C11), constitute approximately 69.1% of the total secondary conflicts. In addition, through-cross conflicts (C8 and C11) result in the highest percentage of the severest grade (G4) secondary conflicts.

The North Carolina Department of Transportation, in its continuing efforts to more fully and effectively use advanced information technology tools to increase institutional productivity and effectiveness in managing its transportation infrastructure, embarked on a study that involved developing a comprehensive and unified enterprisewide information management system. This paper focuses on the issues and needs that emerged as the information system development study evolved. These issues and needs became so significant that they warranted a detailed analysis in and of themselves. It is these issues and needs, which have a degree of universality, that are reported herein. This paper first introduces and discusses the functions of various participating units at state departments of transportation (referred to as stakeholders). Then, the paper identifies the issues and needs that must be fully understood and considered in the development of a unified information management system.

The slip-base design mechanism is used to support signs and luminaries in highways and is designed to break away in crashes with vehicles. This mechanism is intended to minimize occupant injuries by providing reduced resistance to the impacting vehicles. The slip-base mechanism could be sensitive to many design parameters. Conventional design and evaluation of safety performance of these systems by trial and error and crash testing is inefficient, as well as cost prohibitive. Therefore, finite-element (FE) models that can accurately simulate the performance of the slip-base system in various crash scenarios are of essential value. This paper describes dynamic FE models of a slip-base sign support system and its crash performance with vehicles using DYNA3D code. The geometric features, as well as several physical phenomena of components of the slip-base mechanism, e.g., sliding friction, clamping forces, bolt-plate interactions, and plate rupture, are modeled and verified in simulation. The FE modeling methods for the required features are described in detail. A validated model of Bogie and its honeycomb material is used as the impacting vehicle. FE crash simulations of Bogie with flexible honeycomb nose impacting the slip-base sign support are validated using the corresponding instrumented crash tests. The simulation model reveals the correct behavior of the break away system response upon impact. The slipping mechanism and Bogie acceleration and velocity responses are accurate as compared with actual crash test results. The FE approach and this validated model can be exercised in numerous crash scenarios for design optimization of other variations of slip-base systems in size, orientation, etc., or for performance evaluation of impacts with various vehicles.

The Federal Highway Administration has designated Highway Design Practices and Criteria as a high-priority research and development area. New design standards need to be developed to provide quantitative guidance on alignment consistency, based on the safety performance of a series of (not isolated) roadway features. Geometric information collected through a datalog vehicle for the entire State Trunk Highway System in Wisconsin provides the opportunity to identify and analyze such series of roadway features. An algorithm was developed to produce horizontal curve length, degree of curve, deflection angle, and maximum superelevation. The algorithm was validated for a two-lane highway. Software was developed to produce plan views, color-code curves to the left (right), and tangents, and to display numeric information (e.g., length of curve, degree of curve) for any chosen highway segment. Integration of the developed algorithm with a GIS base map was demonstrated. Availability of systemwide geometric information allows exhaustive searches of geometrically deficient highway segments and the identification of curve-tangent-curve combinations with prespecified geometries.

A project-level optimization approach was developed to minimize total pavement cost within an analysis period. Using this approach, the designer is able to select the optimum initial pavement thickness, overlay thickness, and overlay timing. The model in this approach is capable of predicting both pavement performance and condition in terms of roughness, fatigue cracking, and rutting. The developed model combines the American Association of State Highway and Transportation Officials (AASHTO) design procedure and the mechanistic multilayer elastic solution. The Optimization for Pavement Analysis (OPA) computer program was developed using the prescribed approach. The OPA program incorporates the AASHTO equations, the multilayer elastic system ELSYM5 model, and the nonlinear dynamic programming optimization technique. The program is PC-based and can run in either a Windows 3.1 or a Windows 95 environment. Using the OPA program, a typical pavement section was analyzed under different traffic volumes and material properties. The optimum design strategy that produces the minimum total pavement cost in each case was determined. The initial construction cost, overlay cost, highway user cost, and total pavement cost were also calculated. The methodology developed during this research should lead to more cost-effective pavements for agencies adopting the recommended analysis methods.

The response of transverse joints of airfield rigid pavements subjected to wheel load is studied. It covers the linear and nonlinear behaviors of the joint by suitably modeling the concrete as elastoviscoplastic and the dowels with elastoplastic materials. The pavements are assumed to be resting on a Kelvin foundation having no gap in between at any stage. The firmness of soil is included in the study as a parameter in terms of its modulus of subgrade reaction. The static effect of a tire pressure is assumed as a long duration pulse that is applied suddenly and then rests for a long time. A fully 3D finite-element software package with an element library, including brick elements, beam-column elements, spring elements, etc., has been developed for the study. Newmark's step-by-step predictor-corrector implicit algorithm is used to solve the dynamic equilibrium equations. The program is validated with established test results and then used for other studies relating to the distribution of shear force in the dowel group, the load-transfer ratio from loaded slab to unloaded slab through the dowels, etc.

Rutting of bituminous surfaces on the Jordanian highways is a recurring problem. Highway authorities are exploring the use of extracted shale oil and oil shale fillers, which are abundant in Jordan. The main objectives of this research are to investigate the rheological properties of shale oil binders (conventional binder with various percentages of shale oil), in comparison with a conventional binder, and to investigate the ability of mixes to resist deformation. The latter is done by considering three wearing course mixes containing three different samples of oil shale fillers—which contained three different oil percentages—together with a standard mixture containing limestone filler. The Marshall design method and the immersion wheel tracking machine were adopted. It was concluded that the shale oil binders displayed inconsistent physical properties and therefore should be treated before being used. The oil shale fillers have provided mixes with higher ability to resist deformation than the standard mix, as measured by the Marshall quotients and the wheel tracking machine. The higher the percentages of oil in the oil shale fillers, the lower the ability of the mixes to resist deformation.