This paper uses the center difference scheme of Lax-Friedrichs to numerically solve a newly developed continuum traffic flow theory and the kinematic theory of Lighthill and Whitham, and Richards, and it studies the flow-concentration phase transitions in flow containing both shock and rarefaction waves. A homogeneous road with finite length was modeled by both theories. Numerical simulations show that both theories yield nearly identical results for two representative Riemann problems—one has a shock solution and the other a rarefaction wave solution. Their phase transition curves, however, are different: those derived from the new theory have two branches—one for acceleration flow and one for deceleration flow, whereas those derived from the LWR theory comprise a single curve—the equilibrium curve. The phase transition curves in the shock case agree well with certain experimental observations but disagree with others. This disagreement may be resolved by studying transitions among nonequilibrium states, which awaits further development of a more accurate finite difference approximation of the nonequilibrium theory.

Poor coordination of horizontal and vertical alignments can create locations where the available sight distance drops below the required sight distance. Therefore, current design guides have recommended a number of guidelines to enhance the alignment coordination. A better and more quantified approach for alignment coordination can be achieved using a concept, called sight distance red zones, based on 3D analysis. A red zone, based on preview sight distance (PVSD), is defined as a section of the road where a horizontal curve should not start relative to a vertical curve. This paper presents a framework to estimate the required PVSD, which is the sight distance required to see, perceive, and react to a horizontal curve before its beginning. The required PVSD consists of two parts: PVSD on tangent and PVSD on curve. A simple analytical model of PVSD on tangent is presented based on the laws of kinematics. The PVSD on curve was investigated empirically using physical modeling and computer animation. Curves with different radii (500–2,000 m), turning directions (left and right), and configurations (with and without spirals) were simulated. Using the collected data, the effect of curve parameters was examined, regression models for the required PVSD on curve were developed, and preliminary design values for the required PVSD are presented.

In this study, self-reported cyclist collision and fall information from a mail-back questionnaire was analyzed for a sample of 2,945 adult cyclists who commute to work/school in Toronto and Ottawa. Analysis focused on incident frequencies by month, time of day, location, road surface condition, and injury level. These results are presented in order to provide a valuable complement to other sources of bicycle incident data obtained primarily from emergency room hospital records. Only a small percentage of collision and fall incidents resulted in a major injury and would therefore be found in a bicycle accident database compiled from emergency room hospital records. Slightly more, 19.2 and 11.7% of the collisions in Ottawa and Toronto, respectively, were reported to police. The results of the study found that collisions were more sensitive to automobile traffic, whereas falls were more sensitive to the prevailing roadway surface conditions. There was a higher proportion of falls than collisions during the winter months in both cities. However, the severity of injuries from collisions and falls were fairly consistent across time periods. Even when the severity of collisions and falls were considered for different roadway environmental conditions and between roads and off-road, no difference was found. This analysis suggests that minor collisions and falls should be considered in accessing the safety experience of bicyclists.

This paper presents data for 15 four-leg unsignalized intersections. The data concerning traffic volume and conflicts of four levels of severity grades were collected by the use of a video camera. The main objective of this paper is to examine the correlation between various volume definitions and conflicts. By adopting the approach volume rather than the total entry volume, it was found that there is always a basic volume that influences the occurrence of certain types of conflicts. This basic volume is made obvious when considering its effects on the serious severity grades G3 and G4 of the influenced conflict type. It was further concluded that the incorporation of other volume combinations, as an exposure measure, may provide misleading correlation between volume and conflicts, due to incorporating irrelevant traffic volume into the correlation.

Existing methodologies for predicting traffic flows on transportation networks involve a sequential process, often with four stages: trip generation, trip distribution, modal split, and traffic assignment. Although the sequential approach has been applied to hundreds of transportation studies throughout the world for the last four decades, and is still being used in practice today, it has an inherent weakness. That is, its predictions need not be internally consistent. This deficiency has motivated attempts to predict all four steps simultaneously. The objective of this paper is to compare the simultaneous approach, using a Simultaneous Transportation Equilibrium Model (STEM) and the conventional sequential approach, using the Texas Demand Model developed and implemented by the Texas Department of Transportation (TxDOT). This was achieved by applying STEM to the urban transportation network of Tyler, Tex., and then comparing the accuracy of the resulting traffic network flows with the “official” TxDOT estimates. The application results showed that predictions of STEM were consistently better than those of the TxDOT by an average improvement of 25%. These results are certainly encouraging in terms of future application of STEM methodology to other real-world large-scale transportation networks.

This paper introduces a universal classification methodology for discretely sampled sealed bituminous road profile data for the study of shock and vibrations related to the road transportation process. Data representative of a wide variety of Victorian (Australia) road profiles were used to develop a universal classification methodology with special attention to their non-Gaussian and nonstationary properties. This resulted in the design of computer software to automatically detect and extract transient events from the road spatial acceleration data as well as to identify segments of the constant RMS level enabling transients to be analyzed separately from the underlying road process. Nine universal classification parameters are introduced to describe road profile spatial acceleration based on the statistical characteristics of the transient amplitude and stationary RMS segments. Results from this study are aimed at the areas of road transport simulation as well as road surface characterization.

A comprehensive analytical treatment of flexible pavement thermal stresses with variable temperature is presented in this paper. General solutions for equations of equilibrium expressed in terms of displacement and variable temperature are derived by Laplace transformation, Hankel transformation, and Laplace transformation with respect to the time and radial and vertical coordinates, respectively. For multi-layered problems, the transfer matrix method is utilized to obtain the general solutions. The calculated results confirm the importance and the need to account for the thermal stresses in design and analysis of flexible pavement.

This paper examines the effect of dowel looseness on the structural response of jointed concrete pavements. A technique for modeling dowels in 3D finite-element analyses of rigid pavement systems is presented that relies on an embedded formulation of a quadratic beam element. This embedded element permits the efficient modeling of dowel looseness using a nodal contact approach and allows the dowels to be exactly located irrespective of the slab mesh lines. The embedded bending element is extended to include a general bond-slip law, and the practical case of a Winkler foundation sandwiched between the dowel and slab is implemented. The results of parametric studies examining the significance of dowel looseness on the response of rigid jointed pavements to both axle and combined axle and thermal loadings are presented. These studies indicate that significant increases in both slab and soil stresses can be expected due to small gaps (≤0.24 mm) between the dowels and the slabs. The importance of explicitly modeling nonlinear load transfer arising from dowel looseness is also examined, and it is shown that equivalent, back-calculated dowel support moduli should be used with caution when dowel looseness exists.

Parameter characterization of asphalt mixtures at various test temperatures is a crux to the performance evaluation of flexible pavements using the visco-elastoplastic method. But the difficulty of determining the relevant parameters experimentally is that deformations of time independent components and viscous components occur simultaneously in the tested sample. To solve this problem, a measuring system of two loggers was introduced to record the transient and time dependent deformations in creep and recovery tests. Based on the deformation separation, parameters of visco-elastoplastic models of asphalt mixtures proposed by Sides et al. are evaluated. Experiments conducted under four temperatures show that all parameters obtained in this way can be related to the temperature approximately either by a linear function or by a power function. Test results and parametric studies show that viscous response of asphalt mixtures to the stress is particularly strong at high temperatures. It is postulated that the process of transition from initial creep to the secondary or final stage of creep will be accelerated for the asphalt mixtures at high temperatures.

The findings of an extensive literature survey on the structural response of unbound aggregates are discussed in two companion papers. In this paper, a state of the art is presented on resilient stress-strain characteristics of such materials, as well as different modeling techniques. The resilient response of aggregates is affected by several factors with varying degrees of importance. These are presented, and different views on the impact of each individual factor are discussed. Research efforts in the past have resulted in different mathematical models for predicting the resilient response of aggregates under repeated traffic-type loading. The models found in the literature are listed, and their advantages and shortcomings are reviewed. The permanent strain characteristics of unbound aggregates are considered in a separate companion paper.

The permanent strain behavior of unbound aggregates under repeated loading has been studied by many researchers over the years. A summarized review of the research into this area is given based on the literature available to date. Different views from various sources are outlined and discussed. A state of the art is presented regarding the factors affecting the permanent strain development in these materials and the modeling techniques available. This paper is the second of two companion papers discussing the current state of knowledge on the structural behavior of unbound aggregates. The resilient properties of these materials are reviewed in detail in the first paper.

Simultaneous service offers service-oriented organizations, such as the air passenger transportation industry, the opportunity to differentiate themselves by providing superior customer service. The concept of simultaneous service is analogous to the concept of simultaneous engineering. However, while simultaneous engineering strives to minimize product development time, simultaneous service strives to minimize customer processing time. Overall customer processing time is reduced by the identification and simultaneous alignment of previously sequentially executed customer service activities. A simultaneous service approach was applied to the international ticketing counter at a major international airport. This involved developing both equipment and operational policy alternatives to the normal sequencing of the ticketing and baggage check-in process. A total of five alternative simultaneous service approaches were investigated. Simulation analysis of these alternatives indicates that a 36% improvement in customer queue and servicing time was possible with this approach.

The paper deals with the estimation of optimal distribution of cars in a traffic netework by slightly modifying the maximum-entropy principle.

An analytic framework dealing with heat movement in a three-layer pavement structure is set up based on the Fourier-Biot heat conduction equation. Exact analytic solution is obtained. The thermal characteristic frequencies of the pavement structure are derived in terms of the thermal properties of the layers. These frequencies are useful for understanding the recorded temperatures at different depths within a pavement structure. This is demonstrated using actual field data collected in a flexible pavement. Furthermore, this study shows that the thermal wave is significantly attenuated by the surface layer of the structure.