Showing papers on "Fleet management published in 1974"

Minimum fleet size models for transportation systems

Abstract: There is an increasing interest in using computers for scheduling both fleet and crews of transportation systems Programs that accomplish this have to be for a large part heuristic, however for some aspects an optimization approach is feasible and may improve the results Moreover, the heuristic programs may benefit from theoretical studies that increase our knowledge of the processes involved The purpose of this paper is to present a general fleet scheduling model together with a survey of applications to various modes of transportation It will be shown that a general fleetsize formula for transportation systems, that expresses the transportation capacity needed in terms of vehicle departure and arrival patterns, can be applied to various situations: suburban railways, buses and airlines In each of these models the passenger origin-destination statistics are assumed to be given, the vehicle arrivals and departures during the scheduling period (normally a day) constitute the variables Basically these are dispatching models Generally, there is room for another objective, apart from the fleetsize, as the number of schedules with minimum fleetsize is normally large This approach leads to mathematical programming models for suburban railway and airline systems, which are applicable to practical situations, as is illustrated by computational results The bus dispatching model leads to a theoretical model for optimal bus departure rates, as a function of the time of day; the model provides some clues concerning the construction of bus timetables /TRRL/

Fuel Economy of the 1975 Models

Abstract: The fuel economy data obtained from the emission tests run by the US Environmental Protection Agency (EPA) have been used to show passenger car fuel economy trends from model year 1957 to present This paper adds the 1975 model year to the historical trend and concentrates on comparisons between the 1975 to 1974 models The net change in fuel economy for the fleet has been estimated at plus 138% comparing the 1975 models to the 1974 models assuming no model mix change occurs General Motors is responsible for the majority of the fleet average improvement

Demand, supply, and cost modelling framework for demand-responsive transportation systems

Abstract: A comprehensive evaluation framework to aid in the implementation of demand-responsive transportation systems is proposed. The framework consists of demand, supply, and cost models that could be applied at general and detailed levels of decision. General-level models use information from existing demand-responsive operations in the United States and Canada. The models provide estimates of expected ridership, vehicle supply, ridership, and cost of operations as a function of system parameters such as population density, fleet size, fare, travel time, and control center requirements. The use of the models to obtain these estimates is exemplified, and their sensitivity to parametric changes is discussed.

Demand-responsive transportation system planning guidelines

Abstract: Based on the limited empirical information of 12 demand-responsive transportation systems, preliminary planning guidelines have been developed to aid in the design of new demand-responsive systems. These guidelines facilitate the estimation of ridership, fleet size, staff requirement and costs. A summary is also presented of the major characteristics of these 12 demand-responsive systems that are operating in the United States and Canada. This summary illustrates the types of systems that have been recently implemented. They include many-to-many, many-to-few, many-to-one and route deviation systems.

The treatment of capital costs of vehicles in evaluating road schemes

Abstract: There are two ways in which new road schemes may influence capital expenditure on vehicles. Firstly, by improving utilisation of existing vehicles, the size of fleet needed to perform a given volume of work may be reduced. This will clearly reduce the amount of capital tied up in motor vehicles at any point in time, and to the extent that vehicle life is determined by age rather than mileage run, will also yield savings in terms of investment in new vehicles. Secondly, by generating additional road traffic, road schemes may lead to an increase in the stock of vehicles in use.