Estimating daily vehicle usage distributions and the implications for limited-range vehicles

Understanding the potential market for limited-range vehicles is important to planning research and development programs for electric and hybrid vehicles and for gaseous-fueled vehicles as well. Studies of consumer preferences and perceptions have shown vehicle range to be a very important vehicle attribute. Studies of household vehicle use, on the other hand, have suggested that the range requirements most households place on vehicles are quite modest. The latter, however, have been severely limited by the absence of longitudinal data on the usage of individual vehicles. Instead, they have relied on single-day surveys on many vehicles, an inappropriate data source. This study develops a method for estimating daily travel distributions for individual vehicles and applies it to a recent longitudinal survey of miles and days between refuelings for over 2000 vehicles. Every vehicle in the sample has at least 30 consecutive refueling intervals. A variety of measures of “range requirement” are defined and calculated. The results confirm the existence of a substantial potential market (20–50% of all household vehicles) for vehicles with ranges on the order of 100 miles. Future research using these data and this method could describe the nature of vehicles with limited-range needs and the households which own them.     

Productive efficiency and ownership of urban bus services

The established ownership mix of urban bus operations in Australia provides a unique opportunity to investigate the productivity differences between public and private bus service supply. Using duality theory in economics which links economic indices of factor productivity to the cost structure of a firm, we develop empirical measures of total and partial productivity of inputs, and adjust the differences for the effects of ownership status and operating environment. The evidence supports the notion that private supply of public passenger transport in general has performed more efficiently in the past than public supply, although the differences in productivity need not continue in the future.     

an analysis of transportation energy conservation projects in developing countries

Industrialized countries have extensive experience with various transportation energy conservation measures and have been making steady progress in improving the efficiency of their transport sector. Less Developed Countries (LDCs) have also been making progress, but their experience in many aspects of transportation energy conservation is very limited. Development organizations have funded many transportation projects in developing countries, but the vast majority of these projects were designed to improve the transportation infrastructure. Very few transportation energy conservation projects have been implemented and decision-makers face a scarcity of information on effective strategies. This paper gives an overview of transportation projects in LDCs in order to identify those transportation energy conservation measures that offer the greatest potential for LDCs. Two case studies, from Tunisia and Costa Rica, are given to illustrate the issues involved in implementing transportation energy conservation measures in LDCs. Conclusions are drawn to suggest actions for developing countries and for development organizations.Acronyms DECAT Driver Energy Conservation Awareness Training - DSE Direccion Sectorial de Energia (Costa Rica) - GDP Gross domestic product - km Kilometer - LDCs Less Developed Countries - TOE Metric tonne of oil equivalent - USAID US Agency for International Development     

Estimating the value of time: An additional misspecification error

This note is an extension of arguments made in an earlier article by J. Guttman in this journal. It points out a specification error in estimating the value of time when parking costs are added to modal running costs, to create a single cost variable. After developing arguments for separating modal costs from parking costs, estimates for Toronto are provided. These estimates demonstrate the magnitude of this type of aggregation bias.The author is indebted to Adolf Buse, Don Dewees and Richard Westin for helpful comments.     

Highway impacts on regional employment

Economic development is increasingly used by state DOT's as a criterion in arriving at highway funding decisions. However, there exists little evidence in the literature justifying the use of such a criterion, especially since existing techniques only determine correlations between highways and development. In this paper a time-series methodology is developed to differentiate the effects of highways on development from the effects of development on highways. This methodology includes structural plot analysis and causality tests and is based on pooled time-series and cross-sectional data on highway construction expenditures and county employment. The results indicate that increases in highway expenditures do not, in general, lead to statewide increases in employment other than temporary increases in the year of construction. However, in counties that are economic centers of the state, highway expenditures do have a positive long-term effect, i.e. employment increases above the normal trend of the economy. Such gains are apparently counterbalanced by employment losses in counties adjacent to the economic centers.     

Design of Optimal Four-Wheel Steering System

Optimal design of the four wheel steering (4WS) system of the ground vehicle is studied. 4WS vehicles with the optimal control scheme are considered first. General formulation of the optimal control law is developed based on the linear quadratic regulator theory. The vehicle speed function (VSF) based 4WS vehicle with a simple feedback controller is considered as a special case of the optimal system. Two new designs of the VSF 4WS system are proposed and their performances are compared with the optimal 4WS systems and the existing VSF 4WS system. The first system is designed for the maximum stability while the second system is designed to emulate the response of the optimal 4WS vehicle. Advantages of the new VSF designs are discussed.     

Vertical Vibration Analysis of Vehicle/Imperfect Track Systems

Summary This paper studies the vertical vibration of a vehicle traveling on an imperfect track system. The car body and sleepers are modeled as Timoshenko beams with finite length, and the rail is assumed as an infinite Timoshenko beam with discrete supports. Imperfection of the track system comes from a sleeper lost partial support by the ballast. Since deflection of the rail is limited within a certain interval where the vehicle is passing over, the infinite domain problem can be transformed into a finite domain problem with moving boundary. In this work, the equations of motion of the car body, rail and sleepers are discretized first by the finite element method. The discretized equations of motion for the vehicle and track systems are then assembled, respectively. Finally, the Newmark method is applied to obtain the response of the vehicle and track systems at each time step. The effect of the vehicle speed on the response of the vehicle and track systems is investigated.