Uncertainty analysis of the large zone economic module of the simple,efficient, elegant,and effective model (SE3M) of land use and transportation

Integrated land use and transportation forecasting models are used to assist decision-makers in the policy analysis and infrastructure capital improvement selection process. These models are typically given precise, point-estimate inputs that are mathematically linked, through a series of submodels, to forecasted model outputs. These point-estimate inputs represent an unrealistic level of precision and a growing body of research is focusing on statistical techniques to model uncertainty in model inputs and parameters and tracking the effects of this uncertainty through the various submodels to the model outputs. This paper presents an uncertainty analysis of the Large Zone Economic Module (LZEM) of the Simple, Efficient, Elegant, and Effective Model (SE³M) of land use and transportation. Three case-study implementations of the model are used to obtain a reasonably sound approximation of how uncertainty affects LZEM outputs: Guam, Puerto Rico, and Oahu, Hawaii. These case studies were the subject of an early transferability study with SE³M and were selected based on both their insularity and diverse physical, economic, and demographic geographies. The findings of this research demonstrate that LZEM has a robust framework, with the potential to estimate error both in the positive and negative direction under uncertain input/parameter conditions.     

Bridging the gap between multi-objective optimization and spatial planning: a new post-processing methodology capturing the optimum allocation of land uses against established transportation infrastructure

The optimal allocation of multiple land uses constitutes a complex multi-objective optimization problem with unknown feasible objective space and optimal planning alternatives. Despite the effectiveness of evolutionary algorithms to capture the underlying Pareto set of optimum maps, land use planners are bound to pursue the best possible spatial allocation of each use within an enormous population of non-dominated solutions. This article presents a novel post-processing methodology enhancing the comparative evaluation of alternative planning approaches without making any assumptions about the (relative) importance of each objective function. The proposed consolidated post-processing module is applied in a land use planning paradigm, revealing: (a) the existence of substantial planning guidelines whose validity is not affected by the relative significance of each criterion and (b) the variable planning component emerging from the (varying) relative importance of objective functions. Such planning feedback could not be extracted by the exhaustive review of non-dominated maps.     

Are we doing it wrong or do we expect too much? Forces that push authorities to become public transport designers

This paper presents a number of reasons that are responsible for the disappointment of authorities in their operators’ efforts to develop public transport (PT) to the advantage of their travellers. The lessons drawn in this paper are based upon the competitive tendering experience of the authors and upon the results of meetings organised with parties involved in competitive tendering and aimed at exchanging lessons. There appears to be three main causes: (1) there is freedom for the operator, but the contract is bad; (2) there is freedom for the operator, there is a good contract, but there is no market; and (3) there is freedom for the operator, but the operator is not able to use it. The paper concludes with a few perspectives for improvement.     

Questioning the need for full amortization in PPP contracts for transport Infrastructure

PPP contracts most often have durations of between 20 and 35 years, but in some cases even longer. The main reason for this is the wish of the Public side to minimize its financial contribution, by including in the contract many years of revenue generation by the project to help cover the investment contribution of the private partner. Implicit however is the need to fully amortize the initial investment, which in many countries is even included in the relevant legislation.PPP contracts are normally framed around the delivery of a range of services during the lifetime of the contract, those services requiring the initial construction or recovery of an expensive infrastructure. The specification of the financial clauses of the contract requires the estimation of demand for those services over the period of the contract and this is usually taken as the major incidence of uncertainty in the contract. Indeed, experience shows that demand forecasts often fail substantially, in many cases by more than 20%, mostly by excess, as State side project promoters (and the bidding private partners) tend to be excessively optimistic about the development of such demand.But when we consider the nature of these contracts we should recognize the existence of at least two other very important types of uncertainty: first, the socially desirable scope and specification of the services to be offered as technology and social preferences evolve; and second, the policy guidelines relative to the total quantity and the social distribution of those services, as that quantity may be causing congestion in other parts of the system, or it may become important to (positively or negatively) discriminate some user segments.In both cases, it is almost impossible to foresee at the time of writing the initial contract if, when and in what direction such types of socially beneficial changes in the provision of the services would intervene, but this rigidness may bear a great loss of social welfare in relation to a more adjustable framework. This criticism affects not only PPPs but all kinds of concession contracts with long duration, so it is not the “partnership” element that must be questioned but rather the duration of the contract.An alternative way is relatively straightforward: abandon the assumption that these contracts must provide full amortization of the infrastructure, which allows adoption of contracts with a shorter life, and the use of multiple such contracts over the lifecycle of the infrastructure.The first generation contract would still have to face the full cost of the construction, but the private partner would receive the unamortized part at the end of that contract, to be paid by the State, directly from the public budget if no more private participation is wanted, or indirectly through the acquisition fee for the contract to be paid by the partner to the second life segment. But, crucially, the State recovers the right to re-specify the terms of the service to be provided without the need for any indemnity, and also the uncertainty associated with the evolution of demand in that period will be much smaller, as this will be my then a mature system in operation.This may seem to increase the transaction costs for the State as more contracts (although of a similar type, especially from the second onwards) may have to be negotiated and signed. But if we take into consideration the difficulties of the frequently needed renegotiations of long duration contracts and the conditions of asymmetry of information in which the State normally finds itself in such cases, we will conclude that, besides avoiding the loss of welfare due to the poor fit of the contract after 20 years or so, this solution after all may also reduce the transaction costs associated with negotiations over the duration of the traditional contracts.     

A comprehensive analysis of household transportation expenditures relative to other goods and services: an application to United States consumer expenditure data

This paper proposes a multiple discrete continuous nested extreme value (MDCNEV) model to analyze household expenditures for transportation-related items in relation to a host of other consumption categories. The model system presented in this paper is capable of providing a comprehensive assessment of how household consumption patterns (including savings) would be impacted by increases in fuel prices or any other household expense. The MDCNEV model presented in this paper is estimated on disaggregate consumption data from the 2002 Consumer Expenditure Survey data of the United States. Model estimation results show that a host of household and personal socio-economic, demographic, and location variables affect the proportion of monetary resources that households allocate to various consumption categories. Sensitivity analysis conducted using the model demonstrates the applicability of the model for quantifying consumption adjustment patterns in response to rising fuel prices. It is found that households adjust their food consumption, vehicular purchases, and savings rates in the short run. In the long term, adjustments are also made to housing choices (expenses), calling for the need to ensure that fuel price effects are adequately reflected in integrated microsimulation models of land use and travel.     

Fatigue life prediction of welded stiffened 350WT steel plates

The propagation of fatigue cracks under constant amplitude cyclic loading was studied in welded stiffened steel plates. The residual stresses in the stiffened plates were measured using the neutron diffraction strain-scanning technique. A finite element model of the stiffened plate was constructed to simulate the residual stresses by an uncoupled thermal and thermo-mechanical analysis. Both the finite element model and the neutron diffraction measurements indicated that in general the residual stresses were tensile near the welded stiffeners and compressive between the stiffeners and ahead of the starter notch tip. Fatigue testing indicated that the fatigue crack growth rates of the stiffened plates were in general lower than that of a corresponding unstiffened plate, especially near the notch tip where compressive residual stresses existed. Both the finite element method and Green's function predicted the fatigue crack growth rates with reasonable accuracy.     

Hoop stress approximation in offshore design codes

For a circular cylindrical vessel with an elastic material, Lame equations can accurately predict hoop stress variation within the vessel wall. However, because of the complexity involved in Lame formulations they are seldom used in design. In this paper, Lame equations are reproduced in terms of vessel outer and material cross-sectional areas and presented in a very simple format that enables hoop stress calculation without use of any approximation. Lame equations are also presented in terms of diameter-to-wall-thickness ratios in order to perform parametric studies. For a practical range of diameter-to-wall-thickness ratios the Lame hoop stress predictions are compared with approximate solutions of a selected design codes. For a range of loading conditions, comparison of results shows that a number of design codes overestimate the hoop stress. In contrast, a selection of offshore codes is shown to underestimate the hoop stress and, for a certain loading condition some codes ignore the hoop stress effect completely. The present paper also shows how the hoop stress approximation may lead to onerous results when the true wall axial stress is derived based on design code hoop stress formulations. It is concluded that what makes the present hoop stress formulations so important in design is their ability to interpret the mechanics of behavior that Lame equations strived to reveal.     

GPS-based speed collection method for road traffic noise mapping

One of the most difficult and expensive tasks in making noise pollution maps is the collection and processing of the data needed to create acoustic models. In the case of road traffic noise maps, obtaining speed data for light and heavy vehicles a problem that has usually been avoided by using a road’s speed limit or by making assumptions based on experience from similar road types. Here global positioning systems-based techniques are applied for acquiring vehicle speed data and adapted to fulfill the requirements of noise prediction models.     

Designing a non-linear tracking controller for vehicle active suspension systems using an optimization process

In this paper, a new non-linear tracking controller for vehicle active suspension systems is analytically designed using an optimization process. The proposed scheme employs a realistic non-linear quarter-car model, which is composed of a hardening spring and a quadratic damping force. The control input is the external active suspension force and is determined by minimizing a performance index defined as a weighted combination of conflicting objectives, namely ride quality, handling performance and control energy. A linear skyhook model with standard parameters is used as the reference model to be tracked by the controller. The robustness of the proposed controller in the presence of modeling uncertainties is investigated. The performed analysis and the simulation results indicate that both vehicle ride comfort and handling performance can be improved using the minimum external force when the proposed non-linear controller is engaged with the model. Meanwhile, a compromise between different objectives and control energy can easily be made by regulating their respective weighting factors, which are the free parameters of the control law.     

Public perceptions of toll roads: A survey of the Texas perspective

Like many U.S. states, Texas is experiencing shortfalls in transportation funding, along with growing needs for system improvements. Accordingly, the Texas Department of Transportation (TxDOT) is turning to tolling to bridge the funding gap. To assist planning efforts and effectively direct public information, a telephone survey of 2111 Texans was undertaken statewide to gauge public opinion on tolling issues.Some issues yielded a definite consensus among survey respondents. Over 70% agreed on attending to existing roads first, keeping existing roads toll-free, reducing tolls after construction, using revenues within the same region, charging higher tolls for trucks, not imposing SOV tolls, and maintaining the same toll rates during rush-hours. Some opinions varied by region. Austinites were more likely to support additional transportation spending, while residents of the Lower Rio Grande Valley were less supportive of raising the gas tax and of public/private partnerships. Opinions also varied with survey design. In eight places in the survey, optional text was provided or question order was modified to intentionally influence response. For two questions, support for tolling was decreased when information on personal transportation costs and higher gas tax rates in other states was offered. Ordered probit and binomial and multinomial logit models were estimated to assess the impact of demographic and travel characteristics on respondent opinions, and results for key issues are presented here. Opinions across demographic groups also were examined. The survey was successful at measuring opinions on several key tolling issues and should prove a useful tool for transportation planners and policymakers.