Kilometers per Mechanical Breakdown
This indicator is a measure of the mechanical reliability of a fleet. Overall, it will give an indication of the standard of maintenance as well as of general fleet condition. The older and less well maintained a fleet, the lower the number of kilometers per breakdown is likely to be.
The definition of a mechanical breakdown may vary. The most appropriate definition is any mechanical defect which causes or requires the vehicle to stop, and which makes it impossible or unsafe for it to continue with the journey. Defects which prevent a vehicle from commencing a journey, for example if a vehicle fails to start in the morning, should not be included in this calculation; the effect of these defects will be reflected in the figures for availability.
Whatever definition is used, it is important that it is used consistently within an organization so that valid time series comparisons may be made. Kilometers lost due to accidents should be recorded separately, since these indicate safety standards rather than mechanical reliability.
Achievable figures vary considerably, depending on factors such as maintenance standards, types of service, operating conditions, fleet age, and driving standards. A well-maintained fleet of buses operated on city services on good roads and with good driving standards should achieve over 20,000 kilometers per breakdown; at the other extreme, poorly maintained buses operating on services in conditions typical of a developing country may achieve as little as 2,500 kilometers per breakdown, or even less, although a typical urban fleet will achieve between 5,000 and 10,000 kilometers per breakdown.
Within a fleet there will be wide variations between the best and the worst groups of vehicles: for example, in a fleet averaging 7,000 kilometers per breakdown, the newer vehicles may achieve over 30,000 kilometers per breakdown, while the older ones may achieve fewer than 2,000.
Alternatively, this indicator may be expressed in terms of the number of breakdowns per 10,000 kilometers.
Another alternative measure which is sometimes used is the number of breakdowns per day, expressed as a percentage of the number of buses in service. This is less specific since it does not reflect the level of activity, but has the advantage of being much easier to calculate, particularly where accurate kilometer figures are not available.
On this basis, with a fleet averaging 200 kilometers per bus per day and 20,000 kilometers per breakdown, the figure for daily breakdowns in service would be 1%.
