Breakdown theories and complex units--A critique

The paper deals with breakdown theory of units using construction firms' fleets as an example. A firm usually has a fleet of units such as trucks, concrete mixers, compaction plant, etc. An individual unit such as a truck may be regarded as a structured set of components. A component may be relatively simple e.g. tyres, or complex e.g. an engine. The conflicting breakdown theories for units in a fleet are initially stated. Then plausible hypotheses of the location, cause and responsibility of breakdown, and breakdown pattern on units are outlined from studies. Hypotheses are then tested using data from a cross sectional analysis of construction firms with large diversified fleets. The contribution of the paper is to show that complicated units, operating over varying lives, should not be expected to have differing breakdown rates per unit of time whereas the likelihood of failure of individual components increases with time. It also provides some empirical evidence of this assertion.