49 CFR 625.41: Standards for measuring the condition of capital assets.

A capital asset is in a state of good repair if it meets the following objective standards—

(a) The capital asset is able to perform its designed function;

(b) The use of the asset in its current condition does not pose an identified unacceptable safety risk; and

(c) The life-cycle investment needs of the asset have been met or recovered, including all scheduled maintenance, rehabilitation, and replacements.