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• Green signal countdown timers have positive short-term effects on drivers' behavior. • Driving speed and distance to intersection at yellow light affect drivers' behavior. • Risk-taking and risk-averse drivers have different crossing speeds under the timer. • The timer encourages risk-taking drivers to cross intersections at higher speeds. • The timer causes risk-averse drivers to be indecisive while crossing intersections. Introduction: Motor-vehicle crashes at signalized intersections are a significant traffic safety problem. To address this problem, many Asian cities have installed signal countdown displays at signalized intersections, aiming to assist drivers to make correct decisions in response to traffic signals. Method: In this study, we assessed the short-term and long-term effects of green signal countdown timers (GSCTs) on road safety, using a combination of driving simulator experiments and naturalistic observations. Results: In our driving simulator experiments, 80 participants drove at 50 km/h in scenarios in which a car either approached a signalized intersection alone or following another car. In naturalistic observations, short-term (1-week) and long-term (1-year) intersection safety in the presence and absence of GSCTs were compared. These observations revealed that GSCTs reduced the number of red-light-running violations over the short term, but not over the long term. In fact, GSCTs appeared to lead to an overall increase in rear-end crash risk at intersections, as their presence resulted in drivers exhibiting more sudden acceleration and braking, and altered intersection-crossing speeds and patterns. Conclusio ns: The results suggest that GSCTs worsen safety at signalized intersections, and thus their removal should be considered. [ABSTRACT FROM AUTHOR]

• A novel stochastic link-based fundamental diagram model was considered for considering speed heterogeneity. • Random-parameter structures were applied to reveal the unobserved heterogeneity. • Two-stage Bayesian inference was proposed for model calibration. • Effects of rainfall intensity on mean speed and speed variance were quantified. This study aims to establish a stochastic link-based fundamental diagram (FD) with explicit consideration of two available sources of uncertainty: speed heterogeneity, indicated by the speed variance within an interval, and rainfall intensity. A stochastic structure was proposed to incorporate the speed heterogeneity into the traffic stream model, and the random-parameter structures were applied to reveal the unobserved heterogeneity in the mean speeds at an identical density. The proposed stochastic link-based FD was calibrated and validated using real-world traffic data obtained from two selected road segments in Hong Kong. Traffic data were obtained from the Hong Kong Journey Time Indication System operated by the Hong Kong Transport Department during January 1 to December 31, 2017. The data related to rainfall intensity were obtained from the Hong Kong Observatory. A two-stage calibration based on Bayesian inference was proposed for estimating the stochastic link-based FD parameters. The predictive performances of the proposed model and three other models were compared using K -fold cross-validation. The results suggest that the random-parameter model considering the speed heterogeneity effect performs better in terms of both goodness-of-fit and predictive accuracy. The effect of speed heterogeneity accounts for 18%–24% of the total heterogeneity effects on the variance of FD. In addition, there exists unobserved heterogeneity across the mean speeds at an identical density, and the rainfall intensity negatively affects the mean speed and its effect on the variance of FD differs at different densities. [ABSTRACT FROM AUTHOR]

• An integrated space-time network for both train rescheduling and passenger routing is developed for an incident of complete blockage. • A two-layer decomposition approach based on alternating direction method of multipliers (ADMM) algorithm is developed to solve the integrated model. • The model is tested for case studies of Chinese high-speed railway networks. Trains normally run as scheduled in a non-disrupted situation. However, due to external and/or internal factors, trains may deviate from their original timetable during daily operations. To this end, the involved dispatchers are required to reschedule disrupted trains to efficiently transport delayed passengers to their destinations as soon as possible. In this study, we focus on train rescheduling in a seriously disrupted situation where a track segment is completely blocked for a relatively long period of time, e.g., two hours. In this situation, trains cannot pass the disrupted segment, meaning that passengers will be unable to travel as scheduled. We simultaneously rescheduled trains and passenger routes from both the operator's and passengers' perspectives. This integrated train rescheduling and passenger rerouting problem was formulated with an Integer Linear Programming model based on a space-time network. We decomposed the integrated model into two subproblems, a train rescheduling problem and a passenger routing problem, using the alternating direction method of multipliers (ADMM) algorithm. Both subproblems could be further decomposed into a series of shortest path problems for trains or passengers, and solved by a dynamic programming algorithm. Finally, we tested our models and algorithms on both a small hypothetical railway network and a part of the Chinese high-speed railway network. [ABSTRACT FROM AUTHOR]

• Equity is explicitly considered in train-timetabling problem. • Quantitative evaluation the equity issue in train timetabling is developed. • A mixed-integer linear programming model is formulated to solve the problem. • The model is tested for case studies of Chinese high-speed railway networks. High-speed railways are expanding rapidly over the world, providing fast, convenient, and comfortable transport. It is therefore important to ensure that people are not excluded from high-speed railway use due to relatively high ticket prices. We aim to develop a railway timetable according to passenger requirements that explicitly considers social equity by applying variable ticket prices to trains. Specifically, we want to optimize ticket prices for trains operating during off-peak hours to improve accessibility for low-income passengers to improve social justice. A mixed integer linear programming model is formulated to solve our problem. In this timetabling-based model, we not only minimize the total general travel cost from a passenger perspective but also ensure that the revenue of the train company is no less than a specified value and that social equity is maintained at a specific level. To do this, we consider the social equity constraint and the minimum revenue requirement constraint, in addition to the traditional passenger-centric (-oriented) train timetabling-related constraints. Finally, we test our model on both a hypothetical high-speed railway network and the Guangzhou–Nanning and Guangzhou–Guilin high-speed railway network in China. The results demonstrate that the proposed optimization framework can provide a convenient timetable for passengers, adequate revenue for train companies and enhance social equity to meet government targets. [ABSTRACT FROM AUTHOR]

Highlights • A driving simulator experiment and a questionnaire survey are designed. • Self-reported serious fatigue is related to worse driving performance. • Temporal patterns of driving fatigue and performance follow quadratic forms. • A recovery effect and a lagging effect are found in the temporal patterns. • Policies to solve high work intensity during rush hours are suggested. Abstract This study uses a questionnaire survey and a driving simulator test to investigate the temporal patterns of variations in driving fatigue and driving performance in 50 male taxi drivers in Hong Kong. Each driver visited the laboratory three times: before, during, and after a working shift. The survey contained a demographic questionnaire and the Brief Fatigue Inventory. A following-braking simulator test session was conducted at two speeds (50 and 80 km/h) by each driver at each of his three visits, and the driver's performance in brake reaction, lane control, speed control, and steering control were recorded. A random-effects modeling approach was incorporated to address the unobserved heterogeneity caused by the repeated measures. In the results, a recovery effect and a lagging effect were defined for the driving fatigue and performance measures because their temporal patterns were concavely quadratic and had a 1-hour delay compared to the temporal patterns of occupied taxi trips and taxi crash risk in Hong Kong. Demographic variables, such as net income and driver age, also had significant effects on the measured driving fatigue and performance. Policies regarding taxi management and operation based on the modeling results are proposed to alleviate the taxi safety situation in Hong Kong and worldwide. [ABSTRACT FROM AUTHOR]

A group-based adaptive traffic-control method for isolated signalized junctions is developed that includes a hierarchical structure comprising tactical and local levels of signal timing optimization. The control method optimizes the signal timings in adaptive traffic-control systems, and takes full advantage of flexible new technologies to incorporate the most up-to-date traffic information, as collected in real time. The definitions, combinations, and sequencing of the cycle structure stages are generated automatically using a procedure for optimizing the signal-timing plans in response to online data from traffic detectors. This new method provides a wider search space and improves the efficiency of the signal-control systems, thus improving the junction performance, minimizing delays, and maximizing capacity in real time. A multi-resolution strategy is proposed for updating the elements of the signal plans cycle-by-cycle and adjusting the current green signal timing second-by-second. The group-based variables and parameters for the proactive global-optimization method utilize lane-based predictive traffic-flow information, such as arrival and discharge rates, expressed as the slopes of polygonal delay formulas. Therefore, there is a high degree of flexibility in the tactical identification of the optimal signal plan in response to the real-time predicted traffic information, the objective function of the polygonal delay formula, and the direct differential equations for the adaptive group-based variables. The reactive local signal-control policy, which is formed based on the max-pressure strategy, is developed to locally adjust the current green signal time and to accommodate delicate demand fluctuations second-by-second at the fine-resolution level. The most appropriate cycle-structure for the tactical level of control is identified using a group-based global-optimization procedure that takes advantage of the latest available information. In part II of this study (Lee et al. 2017), the effectiveness of the proposed methods is validated based on the actualized mathematical frameworks, computer simulations, and a case study, using the appropriate computer programs. [ABSTRACT FROM AUTHOR]

In part I of this study (Lee et al., 2017), the formulation of a theoretical framework for a group-based adaptive traffic-control method for isolated signalized junctions is presented, which includes tactical and local levels of signal timing optimization. The global level control aims to determine the time-varying cycle structure, with a resolution of cycles, and the real-time adjustment of the green phase, with a resolution of seconds, based on longer-term traffic information observed by traffic detectors. Overall, the purpose of the study is to actualize a multi-resolution strategy for a group-based adaptive signal-control method and establish a microscopic simulation platform to implement the proposed methodology and test its effectiveness. To actualize the global proactive-optimization scheme, in this paper, a rolling-horizon approach to the temporal and spatial variables, signal structures for four-arm intersections, and discrete directional search methods is applied using the developed mathematical framework. The formulation of the group-based max-pressure policy is realized using the logical form of the local reactive-control policy at a typical directional three-lane, four-arm approach to an isolated intersection. The integrated group-based adaptive traffic-signal control is actualized using VISSIM, Fortran, and VBA based on the developed tactical and local levels of signal timing optimization. The results of the computer simulations and the case study presented in this paper show that the integrated group-based adaptive traffic-signal-control logic outperforms the other methods over a wide range of traffic conditions, from free-flowing traffic to extreme congestion. Moreover, the proposed models perform much better than the existing fixed-signal plan and the actuated signal-control in asymmetric traffic conditions. [ABSTRACT FROM AUTHOR]

This paper presents the development of a macroscopic dynamic traffic assignment model for continuum transportation systems with elastic demand. A reactive dynamic user equilibrium model is extended to simulate network equilibrium problems for an urban area with multiple central business districts (CBDs). Each copy of traffic flow reactively makes route choice decisions to minimize the total travel cost from origin to destination, based on instantaneous traffic information from a radio broadcasting service or route guidance system. The elastic demand function for each copy of flow is associated with its total instantaneous travel cost. The model is solved by a cell-centered finite volume method for conservation law equations and a fast sweeping method for Eikonal-type equations on unstructured grids. Numerical experiments for an urban traffic network with two CBDs are presented to verify the rationality of the model and the validity of the numerical method. The numerical results indicate that the model captures some macroscopic characteristics of two copies of flow interacting in time-varying urban transportation systems, e.g., the spatial distributions of the flow density and flux and the path choice behavior in response to elastic demand, and can describe traffic equilibrium phenomena, such as self-organization and traffic congestion build-up and dissipation. [ABSTRACT FROM AUTHOR]

In this study, we develop a mathematical framework to estimate lane-based incremental queue accumulations with group-based variables and a predictive model of lane-based control delay. Our objective is to establish the rolling horizon approach to lane-based control delay for group-based optimization of signal timings in adaptive traffic control systems. The challenges involved in this task include identification of the most appropriate incremental queue accumulations based on group-based variables for individual lanes to the queueing formation patterns and establishment of the rolling horizon procedure for predicting the future components of lane-based incremental queue accumulations in the time windows. For lane-based estimation of incremental queue accumulations, temporal and spatial information were collected on the basis of estimated lane-based queue lengths from our previous research to estimate lane-based incremental queue accumulations. We interpret the given signal plan as group-based variables, including the start and duration of the effective green time and the cycle time. Adjustment factors are defined to identify the characteristics of the control delay in a specific cycle and to clarify the relationship between group-based variables and the temporal information of queue lengths in the proposed estimation method. We construct the rolling horizon procedure based on Kalman filters with appropriate time windows. Lane-based queue lengths at an inflection point and adjustment factors in the previous cycle are used to estimate the adjustment factors, arrival rates, and discharge rates in the next cycle, in which the predictive computation is performed in the current cycle. In the simulations sets and the case study, the proposed model is robust and accurate for estimation of lane-based control delay under a wide range of traffic conditions. Adjustment factors play a significant role in increasing the accuracy of the proposed model and in classifying queueing patterns in a specific cycle. The Kalman filters enhance the accuracy of the predictions by minimizing the error terms caused by the fluctuation in traffic flow. [ABSTRACT FROM AUTHOR]

• The risk-taking behaviors of drunk pedestrians in unfamiliar traffic environments is investigated. • Virtual reality (VR) experiments observe the behaviors of drunk pedestrians in different traffic environments in a safe manner. • Panel data analysis evaluates pedestrians' perceptual-motor response and their habitual crossing performance. • This study provides a basis for foreign travelers and traffic policy makers to address road safety problems and make effective improvements. Statistics indicate that alcohol consumption is heavily involved in tourism, with tourists likely to consume more alcohol than usual when visiting other countries. The risk of traffic collisions is also expected to increase when tourists are exposed to different traffic rules to those of their home country. To explore the crossing behaviors of drunk pedestrians under unfamiliar traffic rules, a virtual reality–based experiment was conducted in this study. The street crossing performances of 53 local pedestrians under different traffic rules, either familiar or unfamiliar to them, before and after alcohol intake were studied. Random-effect regression models were then established, which revealed that the perceptual-motor response was undermined by the effects of alcohol, particularly for young adults. In addition, aspects of the street environment, such as the unfamiliar direction of oncoming vehicles and the presence of traffic direction indicators (i.e., road markings), also contributed to the correct habitual looking behavior of pedestrians. Importantly, these findings clarify the negative effects of alcohol intake on pedestrian crossing performance under unfamiliar traffic rules and provide a basis for foreign travelers and policy makers to mitigate this problem. [ABSTRACT FROM AUTHOR]

The author discusses development of gross domestic product and resources of China as represented by National Bureau of Statistics of China. As per the reports, China is the largest contributor and investor to transport science and technologies. The article also includes tables of publications of transport research and market shares of China and other countries.

This study examines the cellular automata traffic flow model, which considers the heterogeneity of vehicle acceleration and the delay probability of vehicles. Computer simulations are used to identify three typical phases in the model: free-flow, synchronized flow, and wide moving traffic jam. In the synchronized flow region of the fundamental diagram, the low and high velocity vehicles compete with each other and play an important role in the evolution of the system. The analysis shows that there are two types of bistable phases. However, in the original Nagel and Schreckenberg cellular automata traffic model, there are only two kinds of traffic conditions, namely, free-flow and traffic jams. The synchronized flow phase and bistable phase have not been found. [ABSTRACT FROM AUTHOR]

Reliable transport models calibrated from accurate traffic data are crucial for predicating transportation system performance and ensuring better traffic planning. However, due to the impracticability of collecting data from an entire population, methods of data inference such as the linear data projection are commonly adopted. A recent study has shown that systematic bias may be embedded in the parameters calibrated due to linearly projected data that do not account for scaling factor variability. Adjustment factors for reducing such biases in the calibrated parameters have been proposed for a generalized multivariate polynomial model. However, the effects of linear data projection on the dispersion of and confidence in the adjusted parameters have not been explored. Without appropriate statistics examining the statistical significance of the adjusted model, their validity in applications remains unknown and dubious. This study reveals that heteroscedasticity is inherently introduced by data projection with a varying scaling factor. Parameter standard errors that are estimated by linearly projected data without any appropriate treatments for non-homoscedasticity are definitely biased, and possibly above or below their true values. To ensure valid statistical tests of significance and prevent exposure to uninformed and unnecessary risk in applications, a generic analytical distribution-free (ADF) method and an equivalent scaling factor (ESF) method are proposed to adjust the parameter standard errors for a generalized multivariate polynomial model, based on the reported residual sum of squares. The ESF method transforms a transport model into a linear function of the scaling factor before calibration, which provides an alternative solution path for achieving unbiased parameter estimations. Simulation results demonstrate the robustness of the ESF method compared with the ADF method at high model nonlinearity. Case studies are conducted to illustrate the applicability of the ESF method for the parameter standard error estimations of six Macroscopic Bureau of Public Road functions, which are calibrated using real-world global positioning system data obtained from Hong Kong. [ABSTRACT FROM AUTHOR]

Hoogendoorn and Bovy (2004) developed an approach for a pedestrian user-optimal dynamic assignment in continuous time and space. Although their model was proposed for pedestrian traffic, it can also be applied to urban cities. The model is very general, and consists of a conservation law (CL) and a Hamilton–Jacobi–Bellman (HJB) equation that contains a minimum value problem. However, only an isotropic application example was given in their paper. We claim that the HJB equation is difficult to compute numerically in an anisotropic case. To overcome this, we reformulate their model for a dense urban city that is arbitrary in shape and has multiple central business districts (CBDs). In our model, the minimum value problem is only used in the CL portion, and the HJB equation reduces to a Hamilton–Jacobi (HJ) equation for easier computation. The dynamic path equilibrium of our model is proven in a different way from theirs, and a numerical algorithm is also provided to solve the model. Finally, we show two numerical examples under the anisotropic case and compare the results with those of the isotropic case. [ABSTRACT FROM AUTHOR]

In this study, we develop a real-time estimation approach for lane-based queue lengths. Our aim is to determine the numbers of queued vehicles in each lane, based on detector information at isolated signalized junctions. The challenges involved in this task are to identify whether there is a residual queue at the start time of each cycle and to determine the proportions of lane-to-lane traffic volumes in each lane. Discriminant models are developed based on time occupancy rates and impulse memories, as calculated by the detector and signal information from a set of upstream and downstream detectors. To determine the proportions of total traffic volume in each lane, the downstream arrivals for each cycle are estimated by using the Kalman filter, which is based on upstream arrivals and downstream discharges collected during the previous cycle. Both the computer simulations and the case study of real-world traffic show that the proposed method is robust and accurate for the estimation of lane-based queue lengths in real time under a wide range of traffic conditions. Calibrated discriminant models play a significant role in determining whether there are residual queued vehicles in each lane at the start time of each cycle. In addition, downstream arrivals estimated by the Kalman filter enhance the accuracy of the estimates by minimizing any error terms caused by lane-changing behavior. [ABSTRACT FROM AUTHOR]

Background Reading and typing text messages while driving seriously impairs driving performance and are prohibited activities in many jurisdictions. Hong Kong is a bilingual society and many people write in both Chinese and English. As the input methods for text messaging in Chinese and English are considerably different, this study used a driving simulator approach to compare the effects of reading and typing Chinese and English text messages on driving performance. Method The driving performances of 26 participants were monitored under the following conditions: (1) no distraction, (2) reading and typing Chinese text messages, and (3) reading and typing English text messages. The following measures of driving performance were collected under all of the conditions: reaction time (RT), driving lane undulation (DLU), driving speed fluctuation (DSF), and car-following distance (CFD) between test and leading cars. Results RT, DLU, and DSF were significantly impaired by reading and typing both Chinese and English text messages. Moreover, typing text messages distracted drivers more than reading them. Although the Chinese text messaging input system is more complicated than the English system, the use of Chinese did not cause a significantly different degree of distraction. Conclusion Both reading and typing text messages while driving should be prohibited regardless of whether Chinese or English is used. [ABSTRACT FROM AUTHOR]

In transportation and traffic planning studies, accurate traffic data are required for reliable model calibration to accurately predict transportation system performance and ensure better traffic planning. However, it is impractical to gather data from an entire population for such estimations because the widely used loop detectors and other more advanced wireless sensors may be limited by various factors. Thus, making data inferences based on smaller populations is generally inevitable. Linear data projection is a commonly and intuitively adopted method for inferring population traffic characteristics. It projects a sample of observable traffic quantities such as traffic count based on a set of scaling factors. However, scaling factors are subject to different types of variability such as spatial variability. Models calibrated based on linearly projected data that do not account for variability may introduce a systematic bias into their parameters. Such a bias is surprisingly often ignored. This paper reveals the existence of a systematic bias in model calibration caused by variability in the linear data projection. A generalized multivariate polynomial model is applied to examine the effect of this variability on model parameters. Adjustment factors are derived and methods are proposed for detecting and removing the embedded systematic bias. A simulation is used to demonstrate the effectiveness of the proposed method. To illustrate the applicability of the method, case studies are conducted using real-world global positioning system data obtained from taxis. These data calibrate the Macroscopic Bureau of Public Road function for six 1 × 1 km regions in Hong Kong. [ABSTRACT FROM AUTHOR]

In past several decades, many countries have set quantified road safety targets to motivate transport authorities to develop systematic road safety strategies and measures and facilitate the achievement of continuous road safety improvement. Studies have been conducted to evaluate the association between the setting of quantified road safety targets and road fatality reduction, in both the short and long run, by comparing road fatalities before and after the implementation of a quantified road safety target. However, not much work has been done to evaluate whether the quantified road safety targets are actually achieved. In this study, we used a binary logistic regression model to examine the factors – including vehicle ownership, fatality rate, and national income, in addition to level of ambition and duration of target – that contribute to a target’s success. We analyzed 55 quantified road safety targets set by 29 countries from 1981 to 2009, and the results indicate that targets that are in progress and with lower level of ambitions had a higher likelihood of eventually being achieved. Moreover, possible interaction effects on the association between level of ambition and the likelihood of success are also revealed. [ABSTRACT FROM AUTHOR]

Highlights: [•] We consider two effects, perceived potential field and aggregated force vector field, in a crowd. [•] The perceived cost potential is used to navigate pedestrians moving in local low-density domains. [•] The aggregated force vector field is applied to describe the pushing force among pedestrians. [Copyright &y& Elsevier]

Highlights: [•] We show that the original PDUO-C model is not well posed due to an inconsistency in the path-choice strategy under certain conditions. [•] We revisit the PDUO-C problem, and construct an improved model that rectifies the inconsistency in the original model. [•] We propose a self-adaptive MSA that can automatically determine the optimal MSA step size using the least squares method without prior information. [ABSTRACT FROM AUTHOR]

The effect of vehicle emissions on the global climate has prompted increasing concern in the past few decades. Housing development patterns determine people's travel behavior and related vehicle emissions. In this study, we consider a hypothetical city with several central business districts (CBDs) serving several classes of road users, which are continuously distributed over the city. The road network is relatively dense and can be approximated as a continuum. We establish a bi-level model to describe the relationships among housing allocation, traffic volume, and CO2 emissions with a continuum modeling approach. At the lower level, the model achieves the user equilibrium condition of a transport system. At the upper level, it optimizes housing allocation to achieve minimum CO2 emissions. The finite element method, Newton-Raphson algorithm, and convex combination approach are applied to solve the constrained optimization problem established in the bi-level model. A numerical example is then given to illustrate the effectiveness and efficiency of the proposed bi-level approach and solution algorithm in modeling transport demand, traffic intensity, and CO2 emissions with an optimized housing development pattern. [ABSTRACT FROM AUTHOR]

Abstract: Speed is a determining factor in road safety analysis. It is generally believed that an increase in speed harms road safety. However, it can also be argued that driving at high speed reduces the length of time exposure and thus the likelihood of a crash. It is therefore critical to clarify the roles that exposure and speed play in road safety analysis. This study evaluates the relationship between speed and crash risk with respect to distance and time exposure, using disaggregated crash and speed data collected from 112 road segments in Hong Kong. A joint probability model based on a full Bayesian method is applied simultaneously to model crash occurrence and crash severity. In addition, we consider the explanatory variables, including road design, weather conditions, and temporal distribution, in the proposed crash prediction model. The results indicate that average speed plays a significant role in crash risk, despite opposing correlations with respect to distance and time exposure; the correlation between speed and crash risk is positive when distance exposure is considered, but negative when time exposure is used. However, in both cases, speed is positively associated with the injury severity. [Copyright &y& Elsevier]

Abstract: An algorithm for an extended reactive dynamic user equilibrium model of pedestrian counterflow as a continuum is developed. It is based on a cell-centered high-resolution finite volume scheme with a fast sweeping method for an Eikonal-type equation on an orthogonal grid. A high-order total variation diminishing Runge–Kutta method is adopted for the time integration of semi-discrete equations. The numerical results demonstrate the rationality of the model and efficiency of the algorithm. Some crowd pedestrian flow phenomena, such as dynamic lane formation in bi-directional flow, are observed which are helpful for a global comprehension of pedestrian dynamics. Also, the model can be utilized with different potential applications. [Copyright &y& Elsevier]

Abstract: Many road safety researchers have used crash prediction models, such as Poisson and negative binomial regression models, to investigate the associations between crash occurrence and explanatory factors. Typically, they have attempted to separately model the crash frequencies of different severity levels. However, this method may suffer from serious correlations between the model estimates among different levels of crash severity. Despite efforts to improve the statistical fit of crash prediction models by modifying the data structure and model estimation method, little work has addressed the appropriate interpretation of the effects of explanatory factors on crash occurrence among different levels of crash severity. In this paper, a joint probability model is developed to integrate the predictions of both crash occurrence and crash severity into a single framework. For instance, the Markov chain Monte Carlo (MCMC) approach full Bayesian method is applied to estimate the effects of explanatory factors. As an illustration of the appropriateness of the proposed joint probability model, a case study is conducted on crash risk at signalized intersections in Hong Kong. The results of the case study indicate that the proposed model demonstrates a good statistical fit and provides an appropriate analysis of the influences of explanatory factors. [Copyright &y& Elsevier]

Abstract: We consider a transportation network with a set of origins and a set of destinations. Given a set of budgets for the residential and employment developments, and network enhancement, the problem is one of allocating the resources within the system, so that the probability of overloading the links in the network is minimized. For the improved transportation system with new household and employment distribution patterns, a combined distribution and assignment model is used to map the land-use pattern to the link-loading pattern in the network. Assuming that the actual demand of each origin–destination (O–D) pair follows a certain distribution, the road users choose their destination and route in accordance with the user equilibrium principle that is based on the long-run perceived travel cost. Moreover, it is assumed that despite the short-term demand fluctuation, the O–D-link choice proportion remains unchanged for the choices of destination and route, and the stochastic demand of all O–D pairs are independent. Explicit formulae for the mean and variance of the traffic volume on each link are derived. Using the central limit theorem, the probability that the traffic volume does not exceed the link capacity can be estimated, from which we can calculate a network reliability index. This index represents the probability that all links in the network are within the respective capacities. The problem can be formulated as a bi-level program, in which the upper-level sub-program maximizes the network reliability index with respect to the residential and employment allocations and network enhancements, whereas the lower-level subprogram is the combined distribution and assignment model with long-run travel cost functions. The problem is solved by a genetic algorithm. A numerical example is used to demonstrate the effectiveness of the methodology. [ABSTRACT FROM AUTHOR]

Abstract: A predictive continuum dynamic user-optimal (PDUO-C) model is formulated in this study to investigate the dynamic characteristics of traffic flow and the corresponding route-choice behavior of travelers within a region with a dense urban road network. The modeled region is arbitrary in shape with a single central business district (CBD) and travelers continuously distributed over the region. Within this region, the road network is represented as a continuum and travelers patronize a two-dimensional continuum transportation system to travel to the CBD. The PDUO-C model is solved by a promising solution algorithm that includes elements of the finite volume method (FVM), the finite element method (FEM), and the explicit total variation diminishing Runge–Kutta (TVD-RK) time-stepping method. A numerical example is given to demonstrate the utility of the proposed model and the effectiveness of the solution algorithm in solving this PDUO-C problem. [ABSTRACT FROM AUTHOR]

Abstract: Red light violations are a major cause of traffic crashes at signalized intersections. In Hong Kong, prosecutions for red light violations have increased in the past decade. An automated enforcement camera system has been established to combat this prohibited driver behavior. In addition, both demerit points and financial penalties were revised upwards in 2006 to strengthen the deterrent effect of the system. An observational study of driver tendency to run a red light was conducted to evaluate the effectiveness of the combined penalty and camera strategy. Both the short- and long-term effects of the strategy on red light violations were estimated. The influences of factors including temporal variation, the presence of a red light camera, geometric design, and traffic control type were also determined with an aggregate count data model. The results show that the frequency of red light violations significantly decreased after the implementation of the new penalty system, and that the reduction remained significant one year after implementation. Interestingly, no evidence was found for an association between the frequency of red light violations and the presence of a red light camera. [ABSTRACT FROM AUTHOR]

Abstract: Recent studies have shown that the setting of road safety targets is associated with a substantial reduction in road fatalities in the short-term. Although such targets may not themselves be responsible for the reduction in fatalities, they serve as a useful measure of the intention and commitment of road authorities to formulate timely road safety measures that lead to the achievement of the target. A quantified target is regarded as one of the key components of a road safety strategy. However, few studies have examined the degree of commitment and attention of road authorities to such targets in the long-term. In this study, we revisit the effectiveness of the quantified road safety targets set by the Organisation for Economic Co-operation and Development (OECD) countries, but with a different method, time scale, and group of comparison countries. We not only evaluate the associations between quantified targets and road fatality levels, but also measure the changes in the time-series trends in road fatalities over the long-term. The results indicate that all seven treatment countries analyzed experienced desirable changes in the time-series trend in road fatalities during the period under study, which implies an increase in road safety improvement over time. [Copyright &y& Elsevier]

Abstract: We develop a microscopic pedestrian-simulation model in which pedestrian positions are updated at discrete time steps. At each time step, each pedestrian probabilistically selects a direction of movement from a predetermined set according to a logit-type function that considers the dynamics of other pedestrians around, and then selects a step size that satisfies a certain distribution. We perform a number of field experiments on real intersecting pedestrian flows with four different angles. We then validate and calibrate the model using sample data on the deviation angles, step velocities, and velocity–density relations obtained from the experiments. [Copyright &y& Elsevier]

Abstract: This paper takes into account three regimes for the description of traffic dynamics, which include the introduction of a pseudo-density transformed from the velocity, the pressure as a function of the pseudo-density and the relaxation of velocity to equilibrium. The resultant characteristic variables can be used to measure the deviation of the phase state to a desired state and derive physically bounded solutions. Taking the pseudo-density as a conserved variable, the approach is able to describe both equilibrium and non-equilibrium flows in a systematic and unified manner, and thus complex traffic phenomena. The theoretical properties of the model are thoroughly investigated, and numerical examples are used to demonstrate the ability of the model to reproduce some notable traffic phenomena. [Copyright &y& Elsevier]

Abstract: In this paper, we revisit Hughes’ dynamic continuum model for pedestrian flow in a two-dimensional walking facility that is represented as a continuum within which pedestrians can freely move in any direction [Hughes, R.L., 2002. A continuum theory for the flow of pedestrians. Transportation Research Part B, 36 (6), 507–535]. We first reformulate Hughes’ model, and then show that the pedestrian route choice strategy in Hughes’ model satisfies the reactive dynamic user equilibrium principle in which a pedestrian chooses a route to minimize the instantaneous travel cost to the destination. In this model, the pedestrian demand is time varying. The pedestrian density, flux, and walking speed are governed by the conservation equation. A generalized cost function is considered. The reformulated problem is solved by the efficient weighted essentially non-oscillatory scheme for the conservation equation and the fast sweeping method for the Eikonal equation. A numerical example is used to demonstrate the effectiveness of the proposed solution procedure. [Copyright &y& Elsevier]

Abstract: This paper extends the model of urban taxi services in congested networks to the case of multiple user classes, multiple taxi modes, and customer hierarchical modal choice. There are several classes of customers with different values of time and money, and several modes of taxi services with distinct combinations of service area restrictions and fare levels. The multi-class multi-mode formulation allows the modeling of both mileage-based and congestion-based taxi fare charging mechanisms in a unified framework, and can more realistically model most urban taxi services, which are charged on the basis of both time and distance. The introduction of multiple taxi modes can also be used to model the differentiation between luxury taxis and normal taxis by their respective service areas and customer waiting times. We propose a simultaneous mathematical formulation of two equilibrium sub-problems for the model. One sub-problem is a combined network equilibrium model (CNEM) that describes the hierarchical logit mode choice model of occupied taxis and normal traffic, together with the vacant taxi distributions in the network. The other sub-problem is a set of linear and nonlinear equations (SLNE), which ensures the satisfaction of the relation between taxi and customer waiting times, the relation between customer demand and taxi supply for each taxi mode, and taxi service time constraints. The CNEM can be formulated as a variational inequality program that is solvable by means of a block Gauss–Seidel decomposition approach coupled with the method of successive averages. The SLNE can be solved by a Newtonian algorithm with a line search. The CNEM is formulated as a special case of the general travel demand model so that it is possible to incorporate the taxi model into an existing package as an add-on module, in which the algorithm for the CNEM is built in practice. Most of the parameters are observable, given that such a calibrated transport planning model exists. A numerical example is used to demonstrate the effectiveness of the proposed methodology. [Copyright &y& Elsevier]

Abstract: This paper extends the -mapping algorithm to solve a multi-class traffic flow model on an inhomogeneous highway, which is characterized by spatially varying fluxes and very complex waves. In the algorithm, the values of solution variables are mapped onto an intermediate state locally around the cell interface, and then the finite difference WENO reconstruction is applied. The hybrid scheme is consistent with steady flows, and resolves the waves more efficiently than the standard WENO scheme. The algorithm is also applicable to hyperbolic conservation laws with spatially varying fluxes in general. [Copyright &y& Elsevier]

Abstract: In this paper we explicitly construct the entropy solutions for the Lighthill–Whitham–Richards (LWR) traffic flow model with a flow–density relationship which is piecewise quadratic, continuous, concave, but not differentiable at the junction points where two quadratic polynomials meet, and with piecewise linear initial condition and piecewise constant boundary conditions. The proposed model is a generalization of the well-known piecewise linear flow–density relationship in the LWR model. As observed traffic flow data can be well fitted with such continuous piecewise quadratic functions, the explicitly constructed solutions provide a fast and accurate solution tool which may be used for predicting traffic or as a diagnosing tool to test the performance of numerical schemes. We implement these explicit entropy solutions for two representative traffic flow cases and also compare them with numerical solutions obtained by a high order weighted essentially non-oscillatory (WENO) scheme. [Copyright &y& Elsevier]

Abstract: Red light violation is a serious driving offense because of the crash risk and injury severity with which it is associated. In 2006, in Hong Kong both the fine and driver demerit penalty for red light violations were increased to combat the increasing trend of red light violation offenses. Public light bus (PLB) drivers constitute one of the most problematic driver groups because of their high rate of driving offenses and involvement in crashes. This study employed a stated preference (SP) survey to investigate the perceptions of PLB drivers and their attitudes towards the increase in the fine and driver demerit penalty imposed for red light violations, and to measure the influence of these penalties on deterring red light violations by using a multinomial logit model. Possible interventions by driver demographics and the operational characteristics of PLBs in the sensitivity measures were revealed through market segmentation analyses. Both the fine and the driver demerit penalty were significant in deterring PLB drivers from committing red light violations. In addition, the market segmentation analyses found age, marital status, educational level, income level, vehicle class, employment structure, and salary system to be significantly associated with perceptions of the increase in the fine and penalty among the drivers. [Copyright &y& Elsevier]

Abstract: This study attempts to evaluate the injury risk of pedestrian casualties in traffic crashes and to explore the factors that contribute to mortality and severe injury, using the comprehensive historical crash record that is maintained by the Hong Kong Transport Department. The injury, demographic, crash, environmental, geometric, and traffic characteristics of 73,746 pedestrian casualties that were involved in traffic crashes from 1991 to 2004 are considered. Binary logistic regression is used to determine the associations between the probability of fatality and severe injury and all contributory factors. A consideration of the influence of implicit attributes on the trend of pedestrian injury risk, temporal confounding, and interaction effects is progressively incorporated into the predictive model. To verify the goodness-of-fit of the proposed model, the Hosmer–Lemeshow test and logistic regression diagnostics are conducted. It is revealed that there is a decreasing trend in pedestrian injury risk, controlling for the influences of demographic, road environment, and other risk factors. In addition, the influences of pedestrian behavior, traffic congestion, and junction type on pedestrian injury risk are subject to temporal variation. [Copyright &y& Elsevier]

Abstract: Efficient geometric design and signal timing not only improve operational performance at signalized intersections by expanding capacity and reducing traffic delays, but also result in an appreciable reduction in traffic conflicts, and thus better road safety. Information on the incidence of crashes, traffic flow, geometric design, road environment, and traffic control at 262 signalized intersections in Hong Kong during 2002 and 2003 are incorporated into a crash prediction model. Poisson regression and negative binomial regression are used to quantify the influence of possible contributory factors on the incidence of killed and severe injury (KSI) crashes and slight injury crashes, respectively, while possible interventions by traffic flow are controlled. The results for the incidence of slight injury crashes reveal that the road environment, degree of curvature, and presence of tram stops are significant factors, and that traffic volume has a diminishing effect on the crash risk. The presence of tram stops, number of pedestrian streams, road environment, proportion of commercial vehicles, average lane width, and degree of curvature increase the risk of KSI crashes, but the effect of traffic volume is negligible. [Copyright &y& Elsevier]

Abstract: Objectives: : To investigate the effect of centrifugation in circulating mRNA quantitation and to design a new, consistent protocol for it. Design and methods: : The concentrations of β-catenin mRNA, P-selectin mRNA, cytokeratin 20 mRNA, and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA in the plasma, the mononuclear and red cells (MARC) from metastatic colorectal (CRC) patients whose blood samples were centrifuged with 2 different forces, were measured. A new protocol to measure expression profiles in MARC was studied. Results: : When the centrifugal force was increased: (1) the concentrations of all transcripts were dramatically decreased in the plasma samples; (2) only the concentrations of P-selectin mRNA and GAPDH mRNA were significantly increased in the mononuclear cell samples; and (3) their concentrations in the red cells did not change significantly. The new protocol found 9 differential expressed genes. Conclusions: : Centrifugal force causes inconsistent mRNA quantitation in the plasma. The new protocol discovered 9 differential expressed genes for metastatic CRC. [Copyright &y& Elsevier]

Abstract: The Transport Department of the Hong Kong SAR government conducted a trial traffic guidance scheme at the plaza of a busy road tunnel. The scheme involves the placing of reflective road markings on the approach lanes to the toll plaza and the erection of a gantry sign that clearly distinguishes the auto-toll lane. The main purpose of the scheme is to improve traffic flow and traffic safety at the toll plaza. If the scheme is successful, then it will be applied to all other toll plazas in Hong Kong. We conducted an observational before-and-after study to assess the effects of the scheme. We found that the overall lane-changing rate decreased significantly by 23% (0.1 lane crossings per vehicle) at a significance level of 0.05, the pooled conflict count decreased sharply by 44% at a significance level of 0.10, and the crash count also decreased sharply by 38%. The mean travel time for non-auto-toll traffic increased significantly by 30% (8s), whereas that of auto-toll Sunday traffic decreased by 18% (2s). Both changes are statistically significant at a level of 0.05. The results indicate that the trial scheme provided good guidance to drivers. Traffic safety was improved, and the travel time of auto-toll traffic improved in certain periods, although at the expense of non-auto-toll traffic. [Copyright &y& Elsevier]

Abstract: Consider a city with several facilities competing for multi-class users that are distributed continuously over space. Within the city region, the road network is relatively dense and is considered as a continuum. A user equilibrium condition results when users freely make their choice of facilities and their optimal routes within this continuum based on the criterion of minimizing the total facility and travel cost. A logit-type demand distribution function is specified to model the probabilistic choice behavior of destinations for the multi-class users. Furthermore, facility externality is introduced to capture the effect of congestion and economies of scale, as the usage of the facility varies. A mathematical program is formulated for the above complex problem, and a promising solution algorithm is developed. Finally, a numerical example is given to show the feasibility of the mathematical program and the effectiveness of the solution algorithm. [Copyright &y& Elsevier]

Abstract: Since the 1980s, many countries have set quantified road safety targets as part of their comprehensive road safety strategies. This paper studies the association between the setting of quantified road safety targets and road fatality reduction over the past two decades. Both aggregate and disaggregate levels of hypothesis tests are performed on data from 14 countries that set road safety targets during the period 1981–1999. A before-and-after analysis of the treatment and comparison groups is conducted, and the results show that the majority of countries with quantified road safety targets experienced a reduction in road fatalities in this period. Overall, the establishment of quantified road safety targets is found to have an appreciable association with an improvement in road safety. [Copyright &y& Elsevier]

Abstract: Measurement of soil CO2 efflux using a non-flow-through steady-state (NFT-SS) chamber with alkali absorption of CO2 by soda lime was tested and compared with a flow-through non-steady-state (FT-NSS) IRGA method to assess suitability of using soda lime for field monitoring over large spatial scales and integrated over a day. Potential errors and artifacts associated with the soda lime chamber method were investigated and improvements made. The following issues relating to quantification and reliable measurement of soil CO2 efflux were evaluated: (i) absorption capacity of the soda lime, (ii) additional and thus artifactual absorption of CO2 by soda lime during the experimental procedure, (iii) variation in the CO2 concentration inside the chamber headspace, and (iv) effects of chamber closure on soil CO2 efflux. Soil CO2 efflux, as measured using soda lime (with a range of quantities: 50, 100, and 200g per 0.082m2 ground area enclosed in chamber), was compared with transient IRGA measurements as a reference method that is based on well-established physical principles, using several forms of spatial and temporal comparisons. Natural variation in efflux rates ranged from 2 to 5.5g C m−2 day−1 between different chambers and over different days. A comparison of the IRGA-based assay with measurement based on soda lime yielded an overall correlation coefficient of 0.82. The slope of the regression line was not significantly different from the 1:1 line, and the intercept was not significantly different from the origin. This result indicated that measurement of CO2 efflux by soda lime absorption was quantitatively similar and unbiased in relation to the reference method. The soda lime method can be a highly practical method for field measurements if implemented with due care (in terms of drying and weighing soda lime, and in minimizing leakages), and validated for specific field conditions. A detailed protocol is presented for use of the soda lime method for measurement of CO2 efflux from field soils. [Copyright &y& Elsevier]

Abstract: As a new attempt to solve hyperbolic conservation laws with spatially varying fluxes, the weighted essentially non-oscillatory (WENO) method is applied to solve a multi-class traffic flow model for an inhomogeneous highway. The numerical scheme as well as an analytical study is based upon a modified equivalent system that is written in a “standard” hyperbolic conservation form. Numerical examples, which include the difficult traffic signal control problem, are used to demonstrate the effectiveness of the WENO scheme in which the results are in good agreement with the analytical counterparts. [Copyright &y& Elsevier]

Abstract: This paper presents an application of the continuum traffic equilibrium model for the cordon-based congestion pricing problem. The traffic equilibrium model treats densely spaced roads as a continuum over which commuters are continuously dispersed. Suppose in the morning peak-hour, all commuters travel to the central business district (CBD) by taking their individual shortest routes. Their user-optimal route choice behavior, with or without toll pricing, can be formulated as a calculus of variations problem and solved efficiently by the modern finite element method. By plotting the numerical results in a two-dimensional space in the form of contour lines of travel cost to the CBD, one can intuitively identify the level of congestion and the external cost anywhere in the city. Hence, the continuum model and two-dimensional numerical representation allow a traffic planner to select easily one or multiple toll cordon(s) in the city and evaluate the impact of cordon toll charges on the resultant social welfare and user benefits. [Copyright &y& Elsevier]

Abstract: This paper studies the effect of the changed speed limits on accident counts for major roadways in the urban environment of Hong Kong. In 1999–2002, the speed limits of a number of sections of roadway were reviewed and increased. Nineteen of them were major roadways. Their speed limits were raised by 10–20km/h from 50 to 70km/h. Before and after studies were carried out to investigate the changes in accident counts with respect to the set of carefully chosen comparison groups. Qualification tests for these comparison groups were conducted to confirm their suitability for the studies. In the majority of the treatment sites, the accident counts were worse after the increase in speed limits, both for the category of fatal, serious and slight (FSS) accidents, and for the category of fatal and serious (FS) accidents. Overall, the relaxation of the speed limit from 50 to 70km/h increased the FSS accident counts by 15% and the FS accident counts by 1%. The relaxation of the speed limit from 70 to 80km/h increased the FSS accident counts by 18% and the FS accident counts by 36%. [Copyright &y& Elsevier]

This paper presents a procedure for the estimation of origin-destination (O-D) matrices for a multimodal public transit network. The system consists of a number of favored public transit modes that are obtained from a modal split process in a traditional four-step transportation model. The demand of each favored mode is assigned to the multimodal network, which is comprised of a set of connected links of different public transit modes. An entropy maximization procedure is proposed to simultaneously estimate the O-D demand matrices of all favored modes, which are consistent with target data sets such as the boarding counts and line segment flows that are observed directly in the network. A case study of the Hong Kong multimodal transit network is used to demonstrate the effectiveness of the proposed methodology. [ABSTRACT FROM AUTHOR]

In this paper we propose a model and algorithm for solving the equilibrium assignment problem in a congested, dynamic and schedule-based transit network. We assume that the time varying origin–destination trip demand is given. All travelers have full predictive information (that have been gained through past experience) about present and future network conditions and select paths that minimize a generalized cost function that encompasses four components: (a) in-vehicle time; (b) waiting time; (c) walking time; and (d) a line change penalty. All transit vehicles have a fixed capacity and operate precisely as specified in pre-set timetables. Passengers queue at platforms according to the single channel first-in-first-out discipline. By using time-increment simulation, the passenger demand is loaded onto the network and the available capacity of each vehicle is updated dynamically. After each simulation run, the passenger arrival and departure profiles at all stations are recorded and these are used to predict dynamic queuing delays. From such delays, minimum paths are updated and used for the next simulation run. The user equilibrium assignment problem is solved iteratively by the method of successive averages. [Copyright &y& Elsevier]

This paper proposes a qualitative assessment methodology that is comprised of a cluster analysis and an autoregression analysis that assess the effects of various road safety strategies implemented in Hong Kong over the last 10 years. The cluster analysis is first used to group over a hundred road safety projects and programs into a smaller set of meaningful road safety policy strategy clusters. These strategies, together with the trend factor, seasonal pattern, car crashworthiness and meteorological data are then used in the autoregression analysis to relate to the fatality and casualty rates of drivers, passengers, motorcyclists, and pedestrians. This method allows the evaluation of the overall effects of the road safety strategies, and the effects and relative significance of each individual strategy. The evaluation method is described, and the main findings of the study are discussed. [Copyright &y& Elsevier]

ABSTRACT The effectiveness of several leaf water models (‘string-of-lakes’, ‘desert river’ and the Farquhar–Gan model) are evaluated in predicting the enrichment of leaf water along a maize leaf at different humidities. Progressive enrichment of both vein xylem water and leaf water was observed along the blade. At the tip, the maximum observed enrichment for the vein water was 17.6‰ at 50% relative humidity (RH) whereas that for the leaf water was 50‰ at 34% RH and 19‰ at 75% RH. The observed leaf water maximum was a fraction (0.5–0.6) of the theoretically possible maximum. The ‘string-of-lakes’ and ‘desert river’ models predict well the variation of leaf water enrichment pattern with humidity but overestimate the average enrichment of bulk leaf water. However, the Farquhar–Gan model gives good prediction for these two aspects of leaf water enrichment. Using the anatomical dimensions of vein xylem overestimates the effective longitudinal Péclet number (P [sub l] ). Possible explanations for this discrepancy between the effective and the xylem-based estimate of P [sub l] are discussed. The need to characterize the heterogeneity of transpiration rate over the leaf surface in studies of leaf water enrichment is emphasized. The possibility that past atmospheric humidity can be predicted from the slope of the Δ [sup 18] O spatial variation of leaf macrofossils found in middens is proposed. [ABSTRACT FROM AUTHOR]

This paper presents a lane-based optimization method for the integrated design of lane markings and signal settings for isolated junctions. Both traffic and pedestrian movements are considered in a unified framework. Capacity maximization and cycle length minimization problems are considered. The problems are formulated as Binary-Mix-Integer-Linear-Programs (BMILP), which are solvable by any standard branch-and-bound routine. The integer variables include the permitted movements on traffic lanes and successor functions to govern the order of signal displays, whereas the continuous variables include the assigned lane flows, common flow multiplier, cycle length, and starts and durations of green for traffic movements and lanes and pedestrian crossings. A set of constraints are set up to ensure feasibility and safety of the resulting optimal lane markings and signal settings. Numerical examples are given to demonstrate the effectiveness of the proposed method. [Copyright &y& Elsevier]