[Talk-us] Railway start and end dates?

[Nathan Edgars II]

I'm considering using http://wiki.openstreetmap.org/wiki/Key:start_date 
and end_date for some railways, but there seems to be too much 
ambiguity. First, if it's now a highway=*, I'd use start_date:railway 
for when the line opened. But on a railway=disused, wouldn't this be 
when it started to be disused? And on a railway=preserved, you'd 
definitely want to know both when the line first opened and when the 
current tourist operation began. With end_date, there's also ambiguity 
for an abandoned line - should it be when the line last saw service (if 
known)? Or when it was legally abandoned, meaning a shipper can no 
longer take steps to request service (which is closer to OSM's disused, 
though a railbanked trail is technically not actually abandoned)? Or 
when the tracks were removed?