The only practical use of a RR wanting to know how much track they have, like the length of a long a passing siding is, by knowing whether a 7000' train with 6 locos would fit on a siding 6840' passing siding (which it won't) ... and a local train shifter crew would know if they had 14 lumber cars to deliver to the lumber yard that had a 200' rail spur, they're gonna need more track.