The current method of computing the minimum pedestrian green interval for intersection signal timing assumes that the component variables are deterministic. This paper presents a probabilistic method in which the pedestrian start-up time and walking speed are random variables. To establish pedestrian characteristics, data were collected at 14 intersections in downtown, suburban, and tourist areas. The method is based on a safety margin that is defined as the difference between the supplied and demanded green intervals, where the demanded green interval is a random variable. Relationships for the mean and standard deviation of the safety margin of the demanded green interval are developed on the basis of the first-order second-moment analysis. A closed-form solution for the minimum supplied green interval is then derived as a function of the relevant variables, including the vehicular intergreen interval and its component variables. A procedure for establishing the walk and the flashing “don’t walk” intervals is presented. Graphical aids for determining the minimum pedestrian green interval were developed, and application of the proposed method is illustrated using numerical examples. The sensitivity analysis shows that the minimum pedestrian green interval is much more sensitive to the walking speed than the start-up time or their correlation.

Motorcycle braking distance is one of the main components of motorcycle stopping sight distance. Motorcycle braking performance in different situations was not consistent in published literature. This research measured the riders’ braking distances and decelerations to both unexpected and expected objects. For braking maneuvers to an expected object, 89 motorcycle riders released the accelerator and applied the brake as quickly as possible following activation of a light beside the road of both dry and wet pavements. As for an unexpected object, 16 nonalerted subjects were confronted with the need to stop for an unexpected object along the roadway. Vehicle speeds, braking distances, and average deceleration were computed for each braking maneuver. Results showed that the deceleration varied among the riders in which 90% of riders’ decelerations were at least $2.75\mathrm{m}/{\mathrm{s}}^2$ under wet conditions, whereas 90% of all riders decelerated at least $3.3\mathrm{m}/{\mathrm{s}}^2$ on dry pavements. Overall, the motorcycle braking distance is more than the braking distance of passenger cars. These findings suggest that in countries where motorcycles are heavily used, their roads should be investigated for provisions of adequate motorcycle stopping sight distance, especially if the roads were designed according to AASHTO guidelines.

At an isolated signalized intersection, the capacity of the lane group with a short left-turn lane heavily depends on the short lane length and the effective green time allocated for the lane group, as does the capacity of the entire intersection. In this paper, three optimization models are formulated and solved to optimally allocate the lane space and green splits of an isolated signalized intersection with short left-turn lanes. Two intersection performance indexes are proposed to compare the performance of the three models and study its sensitivity to model parameters. The results indicate that all three models can produce satisfactory capacity and delay performances, but it is laborious to find a suitable parameter set when using the objective functions of maximizing intersection capacity and minimizing the weighted sum of the normalized intersection capacity and delay; it is easy when using the objective functions of minimizing intersection delay, maximizing capacity-to-delay ratio, and minimizing delay-to-capacity ratio. Moreover, many sets of noninferior solutions can be obtained by minimizing the delay-to-capacity ratio and adjusting some parameters. Finally, three variations of the formulated models are recommended for use, and the procedure for using these models is given for practical applications.

This paper establishes a mathematical model that can represent the conflicting effects of two pedestrian streams that have an oblique intersecting angle in a large crowd. In a previous paper, a controlled experiment in which two streams of pedestrians were asked to walk in designated directions was used to model the bidirectional pedestrian stream of certain intersecting angles. In this paper, the writers revisit that problem and apply the Bayesian inference method to calibrate an improved model with the controlled experiment data. Pedestrian movement data are also collected from a busy crosswalk by using a video observation approach. The two sets of data are used separately to calibrate the proposed model. With the calibrated model, the relationship between speed, density, and flow is studied in both the reference and conflicting streams, and a prediction is made regarding how these factors affected the interactions of moving pedestrian streams. It is found that the speed of one stream not only decreases with its total density, but also decreases with the ratio of its flow relative to the total flow, i.e., the speed of the pedestrians decreases if their stream changes from the major to minor stream. It is also observed that the maximum disruption that was induced by pedestrian flow from an intersecting angle occurs when the angle is approximately 135°.

A new methodology is proposed to address issues of networkwide effects of highway projects and interdependencies of jointly implementing multiple projects to support optimal investment decisions. Specifically, a multicommodity minimum cost network (MMCN) model is introduced to help obtain link-based traffic volumes, vehicle compositions, and speeds for a highway network that could be used for project benefit estimation using life cycle cost analysis approaches. A hypergraph knapsack model is formulated to identify the best subcollection of interdependent projects to achieve maximized overall benefits for a given budget level. A computational study is conducted using the proposed methodology for tollway capital investment decision making. It is revealed that the overall project benefits with risk and uncertainty considerations for facility construction and treatment costs, traffic forecasts, and the discount rate are significantly lower than the estimated project benefits without risk and uncertainty considerations. In addition, project interdependencies are found to exist for all joint project implementation scenarios. With the continuing growth of budget levels, the overall benefits of projects selected for implementation using the hypergraph knapsack could reach a maximum, beyond which no extra benefits could be obtained. The methodology may be adopted by state and local transportation agencies and metropolitan planning organizations to enhance investment decisions.

In this paper, a finite-element (FE) model including the track super- and substructure components was developed for seismic analysis of railway track. In the developed model, the beam elements were used to define rails and sleepers as components of track superstructures. Moreover, a series of lumped masses with springs and dashpots was considered for modeling the ballast, subballast, and subgrade as track substructure components. In order to validate the FE model, the results of seismic numerical analysis were compared with the outputs of a shaking table test. In the next stage, using the validated FE model, the efficient excited length of the track during the Kobe earthquake was determined around 40 m as the length that created the maximum internal forces and deformations in track components. Finally, using the evaluated effective length and adopting the artificial accelerograms with various peak ground acceleration (PGA) values in the range of 2 to 10 $\mathrm{m}/{\mathrm{s}}^2$ (200 to 1,000 Gal) as input motion, the seismic behavior of the ballasted railway track was studied, and consequently the effect of PGA values on rail buckling length and its deformations as well as rail and sleeper internal forces were investigated.

Dynamic wheel-rail force can be limited to high-frequency components owing to imperfections in the wheel-rail contact surface ($P1$) and may also contain low-frequency components owing to coupled wheel-rail vibrations in phase on the ballast ($P2$). Previous studies on dynamic wheel-rail forces have focused on the quality index of surface roughness (QI) of only rail welds. In this study, the influences of rail surface roughness and track stiffness of a ballasted track on dynamic wheel-rail forces currently employed in high-speed lines were assessed by performing field measurements using actual vehicles running along the service lines. The theoretical dynamic wheel-rail force determined using a previous theory was compared with the dynamic wheel-rail force determined through field measurements. At a constant QI, an increase in the vertical track stiffness caused an increase in $P2$. Therefore, the vertical track stiffness affects $P2$ more strongly than $P1$. Hence, $P1$ is more affected by QI and train velocity than is $P2$. Further, it is inferred that the results of multiple regression analysis obtained using measured data such as QI, vertical track stiffness, and $P2$ can be used to predict the peak dynamic forces acting on ballasted tracks.

Due to the complexity and size of railway interlocking systems, conventional verification and testing techniques are not able to provide sufficient safety assurance. This paper proposes an online observer for safety assurance of railway interlocking systems. The observer provides runtime checking of the states and behaviors of interlocking devices by using a topology-based mathematical model. Route signals, points, and track sections are interpreted in a topological space, and safety properties are expressed as topology theorems. Running synchronously with the interlocking task, the observer conducts safety checks on the route processes and point operations. A case study of an example Chinese railway interlocking system is presented to illustrate the proposed method and its strengths. It is anticipated that this method will provide a fresh means to verify safety properties of railway interlocking systems in addition to traditional testing and verification methods.

Automatic train operation (ATO) is an important part of automatic train control (ATC) systems in urban rail transit. Using computers to simulate the complicated circumstances of train movement to test the operations of certain ATO systems in urban rail transit is an economical, reliable, and safe method. This paper proposes a testing platform for ATO systems, which may be applied to the development of both software and hardware of ATO systems. Specifically, this work firstly studies the theory of traction calculation model of urban rail transit and develops a simulation testing system by building virtual equipment PXI and a software platform based on the programming language LabVIEW8.2. Comprehensive operation results show that the proposed ATO testing platform is capable of simulating the urban rail transit circumstances and accomplishing a variety of testing tasks.

Past design consistency research has demonstrated the relationship between operating speeds and geometric design features on two-lane rural highways. However, little is known about the relationship between geometric design consistency and traffic safety. In this study, design consistency is referred to as the difference between operating speed and inferred design speed, and design consistency density is measured to account for the effect of elements upstream and downstream of the study element. To perform the design consistency–safety evaluation in the present study, geometric design, roadway inventory, crash, and operating speed data were collected along two case-study highways in central Pennsylvania (U.S. 322 and PA 350). Several count regression model formulations were used to explore the statistical association between design consistency and total crash frequency. A statistically significant positive association between geometric design consistency and safety was found. Design consistency surrounding the study elements was also found to increase the expected crash frequency in the study element. The significant effects of design consistency and design consistency density measures on crash frequency for the two case-study sites indicate that there is value in further considering the relationship between design consistency and safety in future research, particularly in the context of the highway safety manual crash-prediction algorithm.

With the rapid increase of automobile ownership, the city of Beijing, China, faces challenging issues with regard to traffic congestion and vehicle emissions. In seeking solutions to these issues, developing and improving public transportation systems is considered one of the most feasible and promising strategies because these systems have high passenger-carrying capacity and low pollution on a per passenger basis. Driving cycles reflect traffic conditions, and thus vehicle emissions, and form a scientific base to further improve bus operations. This paper is intended to develop city-specific driving cycles for transit buses for Beijing. The operational data of 126 buses were collected by using a portable global positioning system (GPS) for three types of bus routes: the bus rapid transit (BRT) line, express line, and regular line. Through analysis of the operating characteristics, a methodology for developing driving cycles is proposed based on the parameter of vehicle-specific power (VSP) distribution. Then, by applying this methodology, driving cycles for BRT, express, and regular lines are developed accordingly. Finally, the developed driving cycles are evaluated. Based on the analysis, the proposed driving cycles are able to reflect the real-world operating characteristics of transit buses better than other driving cycles. Furthermore, the emission factors generated based on the developed driving cycles are lower on average than those predicted by using the default driving cycles in the motor vehicle emission simulator (MOVES).

The relationships between traffic speed, flow, and density under various rainfall conditions on urban roads in Hong Kong are investigated in this study. The effects of rainfall intensities are examined empirically, particularly their effects on the reduction of key traffic stream parameters such as free-flow speed, speed at capacity, and capacity (or maximum flow) on urban roads. Rainfall intensity has been found to have significant impacts on urban road key traffic stream parameters, but not on traffic jam density. Generalized speed-flow and speed-density functions are also proposed and calibrated, taking into account the effects of varied rainfall intensity. The calibrated generalized functions are validated with an independent data set from the same location. The generalized speed-flow and speed-density functions are useful for assessing the performance of urban roads, particularly in cites with relatively high annual rainfall intensity. It is believed that the findings could provide better insights into the effects of rainfall intensity on urban road traffic environments for modeling their impacts on road users’ route choice behaviors.