Road Call
A failure that happens while the vehicle is in service, requiring assistance away from the shop. The most expensive kind of maintenance event and the most visible.
A road call is a failure the public sees. A packer stopped on a route, a bus that does not complete its run and a plow abandoned mid-storm are all operational failures before they are mechanical ones, and they cost much more than the repair.
Road calls per hundred thousand miles, or per unit per year, is the sharpest available check on whether a PM program is actually working. PM compliance says the services were done; the road call rate says whether doing them prevented anything. A fleet with high compliance and a rising road call rate has a schedule problem, an execution problem or an aging problem, and the three are distinguishable by looking at which components fail.
The public-sector sting is that the most road-call-prone assets are often the ones a community notices immediately, and a run of them will reach an elected official long before it reaches a benchmark report.