Taxi services with search frictions and congestion externalities

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 © 2012 John Wiley & Sons, Ltd.     

Estimation of parking accumulation profiles from survey data

Parking accumulation profiles at car parks are time-dependent quantities that require data from lengthy observation surveys. However, it is found that car parks can be clustered into groups based on the similarity in the shape of their accumulation profiles. This procedure increases the efficiency of the survey data collected for this purpose. This paper describes a method developed to estimate aggregate parking accumulation profiles at different districts in a city. The planning of the survey conducted in Hong Kong in the year 2000 and the results of the data analysis are also described.     

Introducing alternative fuel vehicles in Hong Kong: views from the public light bus industry

Hong Kong was the first place in the world to implement a trial scheme to convert all public light buses (PLBs) on the road from diesel to alternative fuel vehicles (AFVs). The scheme, however, did not receive much support from PLB operators. At present, there is a rich literature on households’ demand for AFVs (especially in the USA). However, there have not been many studies about the demand for commercial AFVs in the business and public transport sectors. Since light buses running on alternative fuels are not widely available in the Hong Kong market, a stated preference (SP) survey was conducted to solicit the preferences of PLB operators on eight commercial vehicle attributes and seven forms of government support. The SP data are analyzed by multinomial logit (MNL) models. Detailed analyses on market segmentation and price elasticities follow. The results are of theoretical and practical significance.     

On the reserve capacities of priority junctions and roundabouts

The concept of reverse capacity of a whole junction has been used extensively in the design of signal-controlled junctions. This concept, however, has not been applied to priority junctions and roundabouts, probably because of the complicated demand and supply relationship. When the demands on the approaches to the junction increase, the capacities of those non-priority approaches reduce at different rates. This makes the calculation of reserve capacity of the whole junction not a straightforward task. Using the definition of reserve capacity of a whole junction in Allsop (1972; Transpn Res. 6, 245–255), explicit formulae for the estimation of reserve capacities of priority junctions and roundabouts are derived in this paper. Numerical examples are given to illustrate the usefulness of these formulae.     

Examining the effect of life course events on modality type and the moderating influence of life stage

Transportation - Previous research has demonstrated the relevance of life events to explain changes in travel behavior. Less clear is the moderating role played by life stages on the relationship...     

Sequential optimization approach for the multi‐class user equilibrium problem in a continuous transportation system

We consider a city region with several facilities that are competing for customers of different classes. Within the city region, the road network is dense, and can be represented as a continuum. Customers are continuously distributed over space, and they choose a facility by considering both the transportation cost and market externalities. More importantly, the model takes into account the different transportation cost functions and market externalities to which different customer classes are subjected. A logit‐type distribution of demand is specified to model the decision‐making process of users' facility choice. We develop a sequential optimization approach to decompose the complex multi‐class and multi‐facility problem into a series of smaller single‐class and single‐facility sub‐problems. An efficient solution algorithm is then proposed to solve the resultant problem. A numerical example is given to demonstrate the effectiveness and potential applicability of the proposed methodology.     

Driving situations and driver decisions at road traffic signals

Driver performance in responding to the green-amber-red signal change was studied based on a sample of 2316 last crossing and first stopping vehicles collected by unobtrusive observations at 10 junction approaches in Singapore. Two schemes, a speed-distance diagram (S-D) and an acceleration-deceleration (A-D) diagram, were used to demarcate the driving situations; the driver actions, as revealed outcomes of driver decision-making, were mapped onto these diagrams. The speed-distance diagram can give some indication on what a driver would possibly do. The more complicated acceleration-deceleration diagram is useful for diagnosing the appropriateness of the driver actions. An application of the A-D diagram was demonstrated, and several situations prone to red-running were noted.     

On the convergence of Bell's logit assignment formulation

In Bell M.G.H. (1995. Transportation Research B 29, 287–295), a new logit assignment formulation was developed, which considered all possible paths in the network while still retaining the absence of a need for path enumeration. In his formulation, it presumes that the sum of a geometric series of the weights matrix always converges and hence can be computed as the inversion of a matrix. In this paper, we investigate the convergence properties of this geometric series by means of an eigensystem interpretation which states that the series converges if and only if all the eigenvalues associated with the weights matrix fall into the unit circle in a complex plane. It is found that the geometric series converges unconditionally for acyclic networks, but not necessarily does so for general networks.     

Modeling urban taxi services in road networks: Progress,problem and prospect

Traditionally, many economists have examined the models and economics of urban taxi services under various types of regulation such as entry restriction and price control in an aggregate way. Only recently have we modeled urban taxi services in a network context. A realistic method has been proposed to describe vacant and occupied taxi movements in a road network and taxi drivers' search behavior for customers. A few extensions have been made to deal with demand elasticity and congestion effects together with development of efficient solution algorithms. Calibration and validation of the network taxi service models have been conducted towards their practical applications. This paper presents an overview of the research that has been carried out by the authors to develop network equilibrium models and solution algorithms for urban taxi services, and offers perspectives for future researches.     

Lane‐based optimization of traffic equilibrium settings for area traffic control

Area traffic control is an important element in Intelligent Transportation System (ITS). This paper extends the lane‐based optimization method to a traffic equilibrium network, which improves the operational performance of signal‐controlled network. We formulate a decomposition approach to simultaneously optimize the lane markings and signal settings for a signal‐controlled network that comprises two levels of optimization. At the junction level, the lane markings, control sequence, and other aspects of the signal settings are optimized for individual junctions, whereas at the network level, the group‐based signal settings are optimized to take into account the re‐routing characteristics of travelers and signal coordination effects that are based on a TRANSYT traffic model, which is a well‐known procedure for evaluating the performance of signal‐controlled networks. We use a numerical example to demonstrate the effectiveness of the proposed methodology.