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Driving on curved roads has been recognized as a significant safety issue for many years. However, driver behavior and the interactions among variables that affect driver performance on curves is complicated and not well understood. Previous studies have investigated various factors that influence driver performance on right- or left-turn curves, but have paid little attention to the effects of foggy weather, driver experience and gender on driver performance on complex curves. A driving simulator experiment was conducted in this study to evaluate the relationships between driving behavior on a continuous S curve and foggy weather, driver experience and gender. The process of negotiating a curve was divided into three stages consisting of a straight segment, the transition from the straight segment to the S-curve and the S-curve. The experimental results indicated that drivers tended to drive more cautiously in heavy fog, but the driving risk was still increased, especially in the transition stage from the straight segment to the S-curve. The non-professional (NP) drivers were less sensitive to the impending change in the road geometry, and less skilled in both longitudinal and lateral vehicle control than the professional drivers. The NP female drivers in particular were found to be the most vulnerable group in S-curve driving.

This paper applies a log-linear simultaneous equation model to estimate the returns to scale in a Cobb-Douglas-type bilateral searching and meeting function which characterises the search frictions between taxis and customers. Number of taxis, taxi fare, population, average occupied taxi journey time and disposable income are used as exogenous variables; customer demand, average customer waiting time and average taxi waiting and cruising time in search of each customer are used as endogenous variables. These variables are coupled together through the simultaneous equation model whose parameters are estimated from the Hong Kong Annual Taxi Survey data as well as data from Traffic and Transport Digest and Annual Digest of Statistics. Our calibration results show that urban taxi services in Hong Kong exhibit an increasing return to scale. The established simultaneous equation model can be used to obtain regulatory information useful for decision-making, such as the impact of the restriction over the number of taxi licenses and the fixing of taxi fare structure.

Built upon the previous studies, this paper incorporates both bilateral taxi-customer search frictions and congestion externalities into the economic analyses of the equilibrium properties of taxi markets. We take account of congestion externalities by adopting a realistic distance-based and delay-based taxi fare structure. We first investigate comparative static effects of regulatory variables of taxi fare and fleet size on the market and then examine the properties of the Pareto-efficient solutions for simultaneous maximization of social welfare and taxi profit in the congested market. Copyright (C) 2012 John Wiley & Sons, Ltd.

In this study, global positioning system data from 460 urban taxis are used to develop a time-dependent logit model. The rate of return (ROR, also known as profit per unit time) is used as a factor underlying taxi drivers' searching behaviour for customers. The data also reveal that the search behaviour across districts as well as the decisions towards a particular district in customer-search is strongly related to the daily profile of passenger demand, and that when the overall passenger demand is high, vacant taxi drivers tend to circulate within or wait at the area where their preceding customers got off to find their next customer. The results also show that the ROR is a significant factor that affects the customer-searching strategies of vacant taxi drivers over a day, and is inversely related to the percentage of taxi idling time. More importantly, this paper illustrates that there is a change in searching behaviour over time of day. © 2013 Copyright The Institute of Urban Sciences.

This is the third Special Issue related to papers presented at the 11th International Conference on Advanced Systems for Public Transport (CASPT) held in Hong Kong on 20–22 July 2009. First held in Chicago in 1975, the now triennial CASPT conference series serves as a forum for the international community of researchers and practitioners to address all aspects of public transport operations and systems planning.

Despite several decades of intense effort, theories in traffic and transportation, and methods for transportation planning and operations are still in their infancy of development and refinement, as evidenced by the fast pace of developments of new theories to understand traffic and transportation phenomena and new techniques and methods for transportation planning and operations. In this special issue, a total of 17 papers are collected, which are separated into two parts. The first part focuses on emerging theories in traffic and transportation, and the second on emerging methods for transportation planning and operations. This special issue is organized based on papers selected from the 18th International Symposium on Transportation and Traffic Theory (ISTTT18) held at the Hong Kong Polytechnic University in July 2009. The ISTTT series is the main gathering for the world’s transportation and traffic theorists, for a deeper understanding of traffic and transportation phenomena in order to better plan, design and manage the transportation system. This 18th ISTTT (Lam et al., 2009) celebrates the 50th Anniversary of this premier conference series.

A mutinomial logit model of urban taxi services has been developed for the study of the operational characteristics of the taxi industry, in which it is hypothesised that the customer-searching behaviour of vacant taxis follows a multinomial logit choice model. Although the model is commonly used, little empirical evidence exists to validate the choice mechanism and determine the set of important factors that affect the choice. In the present study, a stated preference survey of 400 taxi drivers was conducted to analyse the customer-searching behaviour of vacant taxis. The results explain how the considered parameters of waiting time, journey time, travel distance and toll affect the driver behaviour when searching for customers. In addition, market segmentation analysis was carried out to study the effects of driver demographics and operational characteristics on the searching behaviour. The parameters that were considered in this section of the study were the age of the driver, taxi ownership, driver experience and marital status.

Built up on the previous studies, this paper incorporates both bilateral taxi-customer search friction and congestion externality into the economic analyses of the equilibrium properties of taxi market. We take account of congestion externalities by adopting a realistic distance-based and delay-based taxi fare structure. We first investigate comparative static effects of regulatory variables of taxi fare and fleet size on the market, and then examine the properties of the Pareto-efficient solutions for simultaneous maximization of social welfare and taxi profit in the congested market.

This paper proposes an equilibrium model to characterize the bilateral searching and meeting between customers and taxis on road networks. A taxi driver searches or waits for a customer by considering both the expected searching or waiting time cost and ride revenue, and a customer seeks a taxi ride to minimize full trip price We suppose that the bilateral taxi-customer searching and meeting occurs anywhere in residential and commercial zones or at prescribed taxi stands, such as an airport or a railway station We propose a meeting function to spell out the search and meeting frictions that arise endogenously as a result of the distinct spatial feature of the area and the taxi-customer moving decisions. With the proposed meeting function and the assumptions underlying taxi-customer search behaviors, the stationary competitive equilibrium achieved at fixed fare prices is determined when the demand of the customers matches the supply of taxis or there is market clearing at the prevailing searching and waiting times in every meeting location We establish the existence of such an equilibrium by virtue of Brouwer's fixed-point theorem and demonstrate its principal operational characteristics with a numerical example. (C) 2009 Elsevier Ltd. All rights reserved

This paper examines the effects of nonlinear fare structures in taxi markets using an extended taxi model with an explicit consideration of perceived profitability. The expected profit, defined as the profit per unit time (inclusive of both occupied and vacant taxi times), that a taxi driver expects to receive from picking up a customer in a particular zone or location, has great impact on the taxi driver's choice of location in the search for customers. The fare structure directly governs the profitability of taxi rides of different distances originating from different locations. With these explicit considerations, the extended model is intended to look into the market effects of adopting a nonlinear fare structure with declining incremental charges. The proposed nonlinear fare structure could help restore a level-playing field for taxi operators whose businesses have been affected by some taxi drivers who resort to practices such as offering fare discounts or accepting requests for discounted fares from passengers for long-haul trips. Analysis of sensitivity of social welfare and profit gain as well as taxi/customer wait/search times is conducted with respect to the parameters in the nonlinear fare structure for the Hong Kong taxi market, and Pareto-improving nonlinear fare amendments are identified that neither disadvantage any customer nor reduce the taxi operators' profits. (C) 2010 Elsevier Ltd. All rights reserved.

As the world is pressed with energy crises and environmental concerns, to address the mobility needs in urban areas, there is a resurgence of interest in encouraging more wide-spread use of public transport in lieu of private cars. The benefits of public transport are many: increased mobility for all, reduced car dependence and consequential needs for highway expansions. The success of this proposition, however, hinges largely on whether public transport offers attractive alternatives to private car usage. It is ideal if public transport services are financially sustainable, with affordable fares, and expedient quality. Despite many decades of intense effort, methods for public transport planning and operations are still in their infancy of development and refinement, as evidenced by the fast pace of developments in both theory and practice.

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 numerica

This paper compares two types of circulatory markings at a double-lane traffic roundabout: the concentric marking scheme and the Alberta marking scheme. The effects of these two marking schemes on drivers' lane choice behavior, delay, and safety, are compared based on data collected from before and after field surveys over a period of 2 years. The results showed that the Alberta marking scheme could better balance the traffic flows on the two circulatory lanes, resulting in higher performance levels.

Since the mid-1990s, the effectiveness of road safety measures in Hong Kong has been weakening. Six administrations in Australia, California, Great Britain (GB), Japan, New Zealand and Sweden are selected to help review the road safety activities in Hong Kong. Nine main components of the road safety strategy, including vision, objectives, targets, action plan, evaluation and monitoring, research and development, quantitative modeling, institutional framework and funding are summarized from the road safety strategies of these overseas administrations and compared to that of Hong Kong. It is found that Hong Kong's road safety activities have to be restructured to make significant improvement. In the future, a new approach structured by the nine different road safety components is recommended. The lessons learnt can be generalized to smooth the progress of other administrations at the Intermediate Stage towards the Advanced Stage of road safety development by using the short-, medium- and long-term approaches.

Under the current taxi licensing system in Hong Kong, holders of taxi licenses are given perpetual operating right in the taxi business. Since 1995, the government has not issued any new taxi licenses. Against this background, the freely traded taxi licenses are often held as an investment asset. When there are active speculative activities, the taxi license premium may be affected more by the general economic conditions than the demand for taxi services and/or changes in the levels of taxi services. In this paper, we use the backward and forward multiple regression methods to develop the level-of-taxi-services (LOTS) and economy- wide (EW) models for understanding fluctuations in the premiums of urban and New Territories (NT) taxis from 1986 to 2002. The results suggest that variations of both urban and NT taxi license premiums can be better accounted for by factors of the EW than the LOTS models. When the policymakers review policy with regard to the taxi license, it is important for them to take a closer look not only at taxi-related factors but also at the economy- wide factors.

Traffic roundabout is a priority junction, whose capacity is typically captured by the entry capacities of individual approaches while considering the effects of conflicting flows. For a single-lane roundabout, entry capacity is traditionally analyzed based on gap acceptance where entering vehicles seek an acceptable gap among the circulating flow. An example of this approach can be found in HCM (2000). This paper provides an extension to this approach for multi-lane roundabouts. Through an analysis of lane utilization, entry capacity is estimated for each entry lane. Reserve capacity is then used as a measure to assess the overall roundabout performance. This paper also studies the sensitivity of drivers' lane choices on the overall capacity of traffic roundabouts. Copyright ASCE 2006.

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\% (8 s), whereas that of auto-toll Sunday traffic decreased by 18\% (2 s). 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. (C) 2006 Elsevier Ltd. All rights reserved.

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. (c) 2006 Elsevier Ltd. All rights reserved.

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.

This paper presents a procedure for the estimation of multiclass origin-destination (O-D) matrices for a highway network. The system consists of a number of vehicle classes. Demand is assigned to the network in a user equilibrium manner. An entropy maximization procedure is proposed to simultaneously estimate the O-D demand matrices of all vehicle classes, which are consistent with the multiclass traffic counts that are observed directly in the network. A case study of the Hong Kong highway network demonstrates the effectiveness of the proposed methodology for a real large-scale network.

This paper develops a mathematical model that is based on the absorbing Markov chain approach to describe taxi movements, taking into account the stochastic searching processes of taxis in a network. The local searching behavior of taxis is specified by a logit form, and the O-D demand of passengers is estimated as a logit model with a choice of taxi meeting point. The relationship between customer and taxi waiting times is modeled by a double-ended queuing system. The problem is solved with a set of non-linear equations, and some interesting results are presented. The research provides a novel and potentially useful formulation for describing the urban taxi services in a network.

This paper proposes a nine- component analytical framework for developing, comparing, and evaluating road safety strategies. The nine components are: ( 1) vision; ( 2) objectives; ( 3) targets; ( 4) action plan; ( 5) evaluation and monitoring; ( 6) research and development; ( 7) quantitative modelling; ( 8) institutional framework; and ( 9) funding. While the first four components are essential for the formulation of a road safety strategy, the remaining components are key to its successful implementation. To demonstrate the usefulness of this comparative framework, we examine the road safety strategies of six selected administrations: Australia, California, Great Britain, Japan, New Zealand, and Sweden. In these case studies, we extract and highlight good practices in the formulation and implementation of their road safety strategies. The proposed framework also provides a systematic approach for assessing road safety strategies in other administrations. The evaluation of the six case studies forms a benchmarking platform for the planning, formulation, and implementation of good practices for road safety strategies.

In most large cities, the taxi industry is subject to various types of regulation, such as entry restrictions and price controls, and economists have examined the economic consequences of such regulation extensively. Unfortunately, in conventional economic analyses of competition and regulation in the taxi industry little attention has been paid to one important issue: congestion externalities due to both occupied and vacant taxi movements together with normal vehicular traffic. This study investigates the nature of equilibrium and regulation in the taxi market by taking account of congestion externalities and adopting a realistic distance-based and delay-based taxi fare structure. The monopoly, the social optimum and the stable competitive solutions are examined and illustrated with a numerical example. (C) 2004 Elsevier Ltd. All rights reserved.

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 tratfic 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. (c) 2005 Elsevier Ltd. All rights reserved.