Abstract
The paper is concerned with records arising in the running and maintenance of a fleet of road passenger vehicles. Such data are inherently variable and unless this is appreciated much effort may be expended in seeking explanations of trends which are of a transient nature and of no real significance. It is necessary to discover the causes of the variability. In doing so it is often desirable to supplement the routine records by information derived from controlled tests; examples of such tests and their interpretation are given.
Records relating to failures and delays to vehicles in service are discussed and a system by which the level of failures is kept under close control is described. Fuel consumption records are then dealt with and the various factors which influence the figures are listed and dilated upon; particular mention is made of the effects of variations in temperature, loadings, traffic density, fuel and lubricating oil characteristics and ‘between-vehicle’ variations. Service tests other than those relating to fuel consumption also receive mention and a method for assessing engine life, employing the ‘Life Table’ technique as used in actuarial work is explained. The paper concludes by stating that if it succeeds in making both manufacturers and operators more aware of the inevitableness of variability it will have achieved its object.
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