Determining the Characteristics of Helical Springs: A Simplification for Application in Railway Suspensions

In a preceding article [1], we had presented the exact methods of calculation for the characteristics of rectilinear and helical springs. As we announced there, an important simplification can be made by replacing the helical spring with an equivalent rectilinear model. This point will be developed in the following article.     

Pedestrianisation: London's Oxford Street experiment

Oxford Street in London, is the capital's principal shopping street and famous throughout the Western World; it is also the most obvious route from the city of London to the West, the Midlands and the North of England.The conflict between its twin roles of shopping centre and major traffic route was demonstrated in its accident record which put Oxford Street top of the list of accident blackspots in London, whilst its location in the most fashionable area of London make the costs of new road construction prohibitive.A comprehensive accident analysis defined the pedestrian/vehicle conflict by time and place and facilitated the detail design of a limited traffic ban with associated rerouting.Considerable uncertainties in prediction of the resulting traffic conditions, in the absence of data on demand elasticity, dominated the design of the experiment and led to the inclusion of an avert chaos policy. Traffic predictions which included details of the probable manner in which congestion would spread were assisted by a new network simulation model developed by one of the authors and described here.The report outlines the history of the experiment from conception to implementation (in record time) and reports some early and generally encouraging results. On the strength of which the Greater London Council has confirmed the scheme (August 1973) and has announced plans for its extension to the remaining half of Oxford Street — from Oxford Circus to St. Giles' Circus — which still carries the full weight of traffic.Previously undertaking doctoral research at Imperial College, London.     

The Random Vibration of a Nonuniform Cantilever Beam with Concentrated Mass

The random vibration of a nonuniform cantilever beam with a concentrated mass at its end, is studied as a simple model of the suspension spring of a motor vehicle. The spectral response of the displacement of the concentrated mass is obtained when the beam is subjected to the random motion of the support. The conditions for the validity of the single degree approximation is also discussed.     

The Dutch mobility panel: Experiences and evaluation

The aim of this paper is to give an overview of the history and research experiences of the Dutch National Mobility Panel. Attention is given to the sampling strategy, the policy goals, and the representativity of the panel. It also tries to evaluate the research outcomes in terms of the original objectives and in view of more general research and policy goals. In sections one and two, a historic overview is given, starting from the first ideas to implement a longitudinal research instrument in transportation planning. In section three, some attention is devoted to longitudinal versus cross-sectional analyses. In section four, the sample design is treated in some detail. Next, various forms of bias are discussed that affect the representativity of the panel. In the sixth section, an overview is given of the research conducted with the data. Some conclusions are given in the final section.     

A comparative study of the dynamic behaviour of a fast patrol boat travelling in rough seas

This paper describes a comparative study between full scale measurements recorded on a fast patrol boat encountering heavy winter seas, south of the Isle of Wight and theoretical predictions accounting for the slamming behaviour of the flexible hull. A hydroelastic approach is adopted and satisfactory agreement between measured and predicted responses demonstrated.     

Transport demand model estimation from traffic counts

Many problems in transport planning and management tasks require an origindestination (O-D) matrix to represent the travel pattern. However, O-D matrices obtained through a large scale survey such as home or roadside interviews, tend to be costly, labour intensive and time disruptive to trip makers. Therefore, the use of low cost and easily available data is particularly attractive.The need of low-cost methods to estimate current and future O-D matrices is even more valuable in developing countries because of the rapid changes in population, economic activity and land use. Models of transport demand have been used for many years to synthesize O-D matrices in study areas. A typical example of this is the gravity model; its functional form, plus the appropriate values for the parameters involved, is employed to produce acceptable matrices representing trip making behaviour for many trip purposes and time periods.The work reported in this paper has combined the advantages of acceptable travel demand models with the low cost and availability of traffic counts. Three types of demand models have been used: gravity (GR), opportunity (OP) and gravity-opportunity (GO) models. Three estimation methods have been developed to calibrate these models from traffic counts, namely: non-linear-least-squares (NLLS), weighted-non-linear-least-squares (WNLLS) and maximumlikelihood (ML).The 1978 Ripon (urban vehicle movement) survey was used to test these methods. They were found to perform satisfactorily since each calibrated model reproduced the observed O-D matrix fairly closely. The tests were carried out using two assignment techniques, all-or-nothing and the stochastic method due to Burrell, in determining the routes taken through the network.requests for offprints     

Queue-dependent vehicle dispatching with options and optimal fleet size

A queue-dependent vehicle dispatching rule, with options to use special vehicles (rented, reserve, shared etc.) for relieving long waiting lines, is considered. The transportation system under consideration has one source terminal and a fleet of N regular vehicles. Passengers are assumed to arrive individually at the source terminal according to a Poisson process. An efficient recursive algorithm is derived to analyse the performance of the system. An average cost criterion is used to determine the firm's fleet size and dispatching strategy for a simpler system. This is a variant of a “Random vehicle dispatching with options” rule proposed by Zuckerman and Tapiero (1980).     

A shipbuilder's view of safety

Shipbuilders do not consider themselves leaders in furthering safety. There has been rapid growth in safety legislation but actual improvement has been modest. Casualty rates could most effectively be reduced in future by removing older ships. The responsibilities for safety in the longer term need consideration.