Qiong Tian

Novel travel cost functions based on morning peak commuting equilibrium

This paper derives two novel travel cost functions by formulating a morning commuting equilibrium model that incorporates traffic congestion based on fundamental traffic flow diagram. The travel cost functions have components to represent traversal cost, waiting queuing costs and early arrival penalty. It is found that the equilibrium travel cost is a concave function of the total demand in the uncongested regime but an increasing linear function of the total demand in the congested regime.

How Do Transit Commuters Make Trade-Offs between Schedule Delay Penalty and Congestion Cost?: Empirical Study in Beijing

The riding behavior of commuters who take transit from home to workplace during peak periods is examined. Costs associated with the schedule delay penalties for early or late arrival and in-vehicle congestion are considered for formulating a mathematical programming model that generates a solution of equilibrium transit riding behavior. Survey data obtained from the No. 13 light rail transit in Beijing are used to show how these commuters make the trade-off between the two costs. A linear relationship was found between the in-vehicle passenger number and the corresponding transit run number. The concavity and convexity characteristics of in-vehicle congestion cost function and the schedule delay cost function should be opposite. In other words, if the schedule delay cost function is concave, the marginal cost of in-vehicle congestion must increase with each additional passenger; that is, the congestion function is convex, and vice versa. Furthermore, the ratio of arrival late and early penalties was estimated by using a piecewise linear schedule delay cost. The ratio is around 1, which is quite different from the finding reported in literature and thus reflects that commuters in different countries may have different attitudes to the schedule delay costs.

A Spatial Model Based on Dynamic Rail Commuter Equilibrium in a Monocentric City

This paper presents a spatial model of rail commuter congestion in a monocentric city to investigate the congestion level on each location along the rail line. A dynamic rail commuter model is formulated to capture the variable crowding environment properties in peak period. Unlike most of the former research studies on monocentric city, we found that not only the total demand of each location will affect the travel cost, but the distribution of the population along the corridor should not be ignored as well. Furthermore, given the functional relations between the total demand and travel cost, a novel spatial equilibrium is established on the equilibrium travel cost. The main contribution of this work is given the general spatial equilibrium a dynamic fundament.

Dynamic Congestion Pricing in Urban Transit System

This paper investigates the first-best dynamic congestion pricing scheme in urban transit system based on the fundamental economic principle of marginal-cost pricing. It is found that for the large capacity urban transit, such as subway, the first-best pricing should be carried out based on segments and the duration of peak period will extend. The closer the intermediate station to the terminal station is, the longer the congestion charging period should be. A numerical example is used to illustrate the application of the proposed pricing framework.

Pareto efficient strategies for regulating public transit operations

This paper investigates how the local authorities could efficiently regulate the public transit, which is operated by a private firm. Both the waiting time at stops and the in-vehicle congestion costs are taken into account to reflect the transit service quality. The Pareto-efficient frontier is derived and three types of regulation strategies, namely Price-cap, Return-on-output and Quantity control, are analyzed and compared. On one hand, although the Price-cap regulation can attract more demand effectively, the private firm will inefficiently supply a lower frequency to keep the cost down. On the other hand, both the Return-on-output (ROO) and Quantity-control regulations are Pareto efficient that can keep the transit system operating along the Pareto-efficient frontier. Especially, Quantity-control regulation seems to be more attractive than ROO as there is no need for the firm’s accounting information. In addition to the investigations on regulation, a new optimal demand-frequency correspondence is also derived that extends the Mohring’s “Square Root Principle” in incorporating transit in-vehicle congestion effects.

Congestion Pricing in Two-airport System with Commercial Operations

This paper studies the congestion pricing in a two-airport system with concession revenues, and analyses the influences of the market propertities on the optimal charge. The main purpose is to help understand the microeconomic behavior of the three parts in the air transportation market and analyse the effect of concession revenues on the optimal charge. We assumed constant return to scale of capacity and linear delay function in our basic model, and seperated the effects of congestion on passengers and carriers.

Equilibrium properties of the morning commuting in a many-to-one corridor network

This paper analyzes the equilibrium properties of the morning commuting pattern in a many-to-one corridor network. In the equilibrium state of the multi-origin corridor, no commuter can reduce his/her total commuting cost by unilaterally changing his/her arrival time or departure time. It is found that commuters living closer to the workplace always join the traffic cohorts of those who live farther away from the workplace. In particular, the more distant a residence to the workplace is, the longer the arrival time period of commuters from that place is. Furthermore, there exists a ‘saturated’ time period for each place, during which the arrival rate of commuters is identical and maximal.

Cellular Automaton Simulation of Emergent Evacuation Considering the Classroom Seats Arrangement

An improved CA model is adopted to simulate the evacuation process in a classroom. It is found that the funnel shape aisle is most efficient, which is consistent with previous studies. Two evacuation time indicators, namely the average evacuation time (AT) and the longest evacuation time (LT), are used in simulations to show the effectiveness and efficiency of the system.

A Mixed Traffic Flow Model Based on a Modified Cellular Automaton in Two-Lane System

Based on the basic symmetric two lane cellularautomaton model(STCA),we propose a modifiedSTCA(MSTCA)for mixed traffic flow.In MSTCA,theheadway also could be used for lane changing,andthen the length for safety criterion would be extended alot.Lane changing region and first cell for lanechanging on the other lane could be located.Thesituation while there are successive vehicles satisfiesboth the safety criterion and the motivation for lanechanging;vehicles ahead would own lane changingpriority.Both the two factors will influence thefrequency of lane changing;eventually affect the totaltraffic flow.Simulation results show that the MSTCAcould acquire higher value of flux and reproduce morerealistic features of the mixed traffic flow.

Ramp Metering Strategies in a Corridor Network

In this paper, which regards highway capacity as scarce resource, we study the ramp metering strategies that have a great effect on commuters’ travel behavior. A spatial residence location problem has been incorporated in the travel choice model. Two representative strategies, namely space equality and commuter equality, are investigated. It has been proven that both strategies attract the same total trip demand,. However, while space equality will have less social cost than commuter equality, this is not consistent with our general belief. For long-term planning purposes, local authorities should insist on adopting the space equality ramp metering strategy, which can alleviate traffic congestion and cause no harm to total demand.