increase with kilometerage/runs (unless you're using miles, then mileage).
Locomotive utilization should be measured in several ways:

* Time utilization, in locomotive-hours, which should then be split into the different types of utilization listed above;
* Distance utilization, in locomotive-kilometers, the total kilometerage run by the locomotive being generally split into passenger trains, freight trains and other uses (light running, switching, run between depot and station or yard, etc.); kilometerage run by cold locomotives will generally not be included in the kilometerage run by the locomotive;
* Total output utilization, in gross trailing ton-kilometers hauled, with a split between freight trains, passenger trains and other uses; and
* Production, in net ton-kilometers hauled for freight trains, or passenger-kilometers moved for passenger trains. Where the locomotive fleets are segregated according to freight versus passenger, this will permit two productivity measures: where the fleets are not separated, the best measure may be a combined measure of "traffic units," which is the sum of ton-kilometers and passenger-kilometers.2/

--------------------------------------------------
Note added at 2005-11-06 23:13:30 (GMT)
--------------------------------------------------

Actually I prefer Segei\'s response, but then I\'m not on the metric system, so I don\'t know if metric-Europeans use \"mileage\" for \"kilometerage.\"