It's the accountants telling operations when portions of the fleet are worthless and are at the end of their lives. After which any serious repairs cause the car to be white lined.
Mark
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But not at the time the depreciation ended, because I doubt they had to run a forty year depreciationschedule. After the car is depreciated down to it's scrap value, it's essentially free, until it needs major repairs, and those were looked at as cost of upgrades vs. potential additional life.
The fact remains, though, that the company needed to know what they owned at any given time, if for no other reason than to set the asset value of the company.
