I'm not really sure which metric is better but one logic of using per hour is that I think vehicle breakdown occurs more likely the more hour they're active, no

I'm not really sure which metric is better but one logic of using per hour is that I think vehicle breakdown occurs more likely the more hour they're active, not the more distance they travelled https://www.lytx.com/blog/measuring-engine-miles-to-hours-to-improve-fleet-management https://www.lytx.com/blog/measuring-engine-miles-to-hours-to... . Also chances of external condition like weather ruining your trips are also more likely with more time because forecasting can only go so far.