Equilibria of bilateral taxi–customer searching and meeting on networks

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.     

Tests on ultimate strength of hull box girders made of high tensile steel

The experimental results of the collapse of three box girders subjected to pure bending moment are presented. The structures are made of high tensile steel of 690 MPa of nominal yield stress reinforced with bar stiffeners of the same material. The moment curvature curves are presented covering the pre- and post-collapse regions. The modes of collapse for each box girder are discussed considering the variation on the panel's slenderness. The concept of efficiency of high tensile steel structures is introduced. The concept is very useful to identify the governing parameters affecting the ultimate strength of 3D structures under predominant bending moment.     

Socio-demographic and built environment influences on the odds of being overweight or obese: The Atlanta experience

This paper explores the association of socio-demographic and built environment characteristics on the odds of being overweight and obese using data from the Atlanta SMARTRAQ travel survey. A new methodological framework based on a multinomial logit (MNL) model and an enhanced odds ratio plot is presented. The use of an MNL model overcomes limitations of many prior studies that employ a sequence of binary logit models to examine multiple weight categories. The use of an enhanced odds ratio plot provides important information into the relative importance of socio-demographic and built environment characteristics. Several new findings for the Atlanta area result from this study. Socio-demographic variables, including age and educational attainment, exhibit a non-linear relationship with the odds of being overweight or obese. Gender, age, ethnicity, and educational attainment are strongly associated with the odds of being overweight or obese, while income and number of students between 5 and 16 years old in the household have smaller effects. Built environment characteristics such as increased net residential densities and enhanced street connectivity are associated with reductions in the odds of being overweight and/or obese. Relative to socio-demographic variables, however, such built environment characteristics have a much smaller impact on describing the odds of being overweight or obese.     

Net tax incidence for urban public transit subsidies in New Zealand

This paper examines the impact of policy changes in the funding of New Zealand public transit modes.These changes, introduced in 1983, are evaluated in terms of the net incidence of public transit subsidy assistance, taking into account its source of funding and the income class of those commuters benefiting from the subsidy. The general conclusion is that the net incidence of subsidy assistance remains progressive (i.e., a transfer from high to low income commuters) following the introduction of shared funding on the predominant public transit modes (rail and bus), sourced from income tax (central government) and property tax (regional/local government). However, because of the predominance of medium to high income commuters on rail vis-a-vis bus and the traditional source of funding on these modes in terms of income tax (a progressive tax source) and property tax (a regressive tax source), the degree of progressivity previously associated with public transit subsidies has now substantially reduced.The analysis and opinions expressed in this paper are the responsibility of the author alone and do not purport to represent the views of the Ministry of Transport.     

Cost-time Minimization in a Transportation Problem with Fuzzy Parameters: A Case Study

In real world applications the supply, the demand and the transportation cost per unit of the quantities in a transportation problem are hardly specified precisely because of the changing economic and environmental conditions. It is also important that the time required for transportation should be minimum. In this paper a method has been proposed for the minimization of transportation cost as well as time of transportation when the demand, supply and transportation cost per unit of the quantities are fuzzy. The problem is modeled as multi objective linear programming problem with imprecise parameters. Fuzzy parametric programming has been used to handle impreciseness and the resulting multi objective problem has been solved by prioritized goal programming approach. A case study has been made using the proposed approach.     

Development of models for predicting roadside nitrogen dioxide concentrations and their evaluation against datasets measured in Dublin,Ireland

Different methods for predicting levels of roadside NO₂ from NO_x concentrations have been proposed. Prior work suggests that either a linear or a logarithmic relationship exists among the roadside NO₂ and NO_x concentrations. We modify and compare those methods with new formulations based on the principles of the original methods for datasets pertaining to Dublin. A new relationship based on the power law is developed to better model the decay of the ratio of (NO₂/NO_x)_road ratio with increasing NO_x concentration. These formulations are compared and examined at two study sites: at an intermittently congested urban street canyon and a free-flowing motorway.     

Federal‐state revenue sharing and resource management under outer continental shelf lands act section 8(g)

Abstract

Section 8(g) was added to the Outer Continental Shelf Lands Act (OCSLA) in 1978. It mandated sharing of the revenues from tracts that included oil and gas pools underlying the federal‐state boundary 3 miles offshore. Revenues were to be split based on agreements negotiated by the secretary of Interior and the relevant coastal state governor or “fair and equitable”; divisions made by the federal district courts. Only one agreement was concluded. Texas and Louisiana sued to force distribution of their shares of $6.1 billion in 8(g) funds held in escrow. In 1986 Congress divided the escrowed 8(g) revenues approximately 27 percent to the adjacent states and 73 percent to the federal government and legislated the same split for all future 8(g) revenues. This article examines the complex issues that section 8(g), as amended, raises for the management of federal and state submerged lands. Cooperative federal‐state approaches to implementing amended section 8(g) are reviewed. Section 8(g)'s broader implications as the only federal‐state ocean resource, revenue‐sharing mechanism currently in place also are addressed.