K. I. Wong

Demand-supply equilibrium of taxi services in a network under competition and regulation

Abstract This paper investigates the nature of demand–supply equilibrium in a regulated market for taxi service. Distinguished from conventional economic analysis, a network model is used to describe the demand and supply equilibrium of taxi services under fare structure and fleet size regulation in an either competitive or monopoly market. The spatial structure of the market such as the form of road network and the customer origin–destination demand pattern are explicitly considered. The model can determine a number of system performance measures at equilibrium such as utilization rate for taxi and level of service quality, and predict the effects of alternative regulations on system performance. The model can thus be used as a policy tool by the regulator to ascertain appropriate taxi regulations such as the selection of taxi fleet size and fare structure. A case study in Hong Kong was conducted to illustrate some interesting findings.

Modeling urban taxi services in congested road networks with elastic demand

This paper extends the simple network model of urban taxi services proposed by Yang and Wong (Yang, H., Wong, S.C., 1998. Transportation Research B 32, 235-246). The extensions include incorporation of congestion effects, customer demand elasticity, reformulation of the model and development of a new solution algorithm. Instead of the previous characterization of pure taxi movements in a network by a system of nonlinear equations, a two-level model formulation is proposed for taxi movements in congested road networks. The bi-level problem is a combined network equilibrium model that describes simultaneous movements of vacant and occupied taxis as well as normal traffic in a user-optimal manner for given total customer generation from each origin and total customer attraction to each destination. The upper-level problem is a set of linear and nonlinear equations ensuring that the relation between taxi and customer-waiting times and the relation between customer demand and taxi supply are satisfied. The lower-level problem can be solved by the conventional multi-class combined trip distribution and assignment algorithm, whereas the upper-level problem is solved by a Newtonian algorithm with line search. A numerical example is presented to illustrate the proposed model and algorithm and demonstrate the characteristics of the taxi services in congested road networks.

Solution of the Dial-a-Ride Problem with multi-dimensional capacity constraints

The Dial-a-Ride Problem (DARP) consists of planning routes and schedules for picking up and delivering users within user-specified time windows. Vehicles of a given fleet with limited capacity depart from and end at a common depot. The travel time of passengers cannot exceed a given multiple of the minimum ride time. Other constraints include vehicle capacity and vehicle route duration. In practice, scheduling is made more complicated by special user requirements and an inhomogeneous vehicle fleet. The transportation of elderly and handicapped people is an important example, as space for wheelchairs is limited and a lift is required. In this study, we present a modified insertion heuristic to solve the DARP with multi-dimensional capacity constraints, and the performance of the proposed algorithm is tested in simulation. We show that the proposed methodology is effective when compared with the classic algorithms.

A combined distribution, hierarchical mode choice, and assignment network model with multiple user and mode classes

Honoring David Boyce for his legendary contributions to the fields of transportation modeling and regional science, the chapters in this festschrift highlight and analyze state-of-the-art and state-of-the-practice methodologies and theories in transportation modeling, regional and urban planning.

A sensitivity-based solution algorithm for the network model of urban taxi services

The objective of this study is to develop an efficient solution algorithm for a network model for urban taxi services with elastic demand in a congested road network. This model can serve as a tool to evaluate the level of taxi service in terms of taxi utilization, waiting times of taxis and passengers, taxi demands, cost and revenue generation of taxis, with respect to the regulatory measures such as taxi fleet and fare control. The study proposes a new sensitivity-based solution algorithm in which the computation of the Jacobian matrix in a set of linear and nonlinear equations (SLNE) will take into account the characteristics of the combined network equilibrium model (CNEM). Sensitivity analysis is used to calculate the derivatives of the variables and constraint multipliers in the CNEM with respect to the perturbation parameters in the SLNE. Described is the formulation of the taxi model with elastic demand in a congested road network. The new sensitivity-based solution algorithm is proposed and a wide range of computational experiments are conducted to illustrate the computational efficiency of the proposed sensitivity-based algorithm over the original newtonian one.

Economic Performance of Property Companies in Hong Kong

This paper examines the economic performance of 16 property companies in Hong Kong, and how well they do in comparison with Singapore property companies. The results show that Hong Kong property companies that diversified into other sectors appeared to perform better than those focused solely in real estate. Property companies in Hong Kong generally achieved higher rate of returns on their capital invested than Singapore property companies. Government financial assistance for private homeownership is believed to play an important role in the relatively better performance of Hong Kongs companies, particularly after 1997. Meanwhile, firms in Hong Kong are exposed to higher weighted average cost of capital due to higher business risks, in addition to higher interest rate stemmed from a linked exchange rate system. On the whole, property companies in both Singapore and Hong Kong do not perform well from an Economic Value‐Added (EVA) perspective, but this does not necessarily mean that they are poorly managed. The empirical results show that the performance of a company is influenced dramatically by profits generated from the sale of non‐property assets.

An Estimation Of Efficient Time-Varying Tolls For Cross Harbor Tunnels In Hong Kong

This work estimates the distribution of a time-varying toll over a 24-hour period that minimizes the combined queue length of the three tunnels that traverse Hong Kongs Victoria Harbour, taking into account institutional constraints. Our results reveal that switching from a flat toll to a time-varying toll scheme would eliminate all existing tunnel queues. We argue that optimal tunnel tolling, coupled with the nonstop electronic toll collection mechanism already in place, could be the first step toward the implementation of electronic road pricing in Hong Kong. Optimal tolling would obviate the need to build a fourth harbor crossing in the near future.

On dynamic demand responsive transport services with degree of dynamism

The operation of a demand responsive transport service usually considers advanced and real-time requests. Previous studies focused on solution algorithms for routing and scheduling challenges of a pickup and delivery problem with time windows, but the operational issues of the overall system performance under a partially dynamic environment have not been investigated. In this article, we explore the operating efficiency of a dispatching system with a degree of dynamism (i.e. a ratio of dynamic requests). It is found that a dispatching system incurs higher transportation costs and accepts fewer requests when the request arrivals are partially dynamic, as compared to static or fully dynamic scenarios. Operational policies are derived for the dispatcher to avoid the inefficient range of degree of dynamism if future demand can be anticipated.

Short-term travel time estimation and prediction for long freeway corridor using NN and regression

Travel time information is a fundamental component in Advanced Traveler Information System. In this paper, we propose a short-term travel time estimation and prediction framework for long freeway corridor, considering measurements from vehicle detectors (VD) and floating car data (FCD). The modeling approach is based on a modified Nearest-Neighborhood (NN) model with threshold and a regression model capturing the within day variations. The advantages are that our approach allows for missing data without the need of data imputation in real-time, and is suitable for travel time prediction of long corridors. The validation analysis using an 88 km long section of freeway shows satisfactory results.

Travel characteristics in Macao: a small and gaming-led tourism city

Macao is known for its tourism and gaming industry. It is small in size, densely populated, and connected to Mainland China with a tremendous number of visitors every year. This paper presents the travel characteristics in Macao. Part of the results is based on the household travel survey completed in 2009, which is the first travel characteristics survey to collect the attributes, preferences, and behavior of travelers. Some unique characteristics in the transportation system including cross-border travels and tourism are also discussed. The findings will enrich our understanding of travel characteristics in a small and tourism-oriented city.