If I may ask some clarifications on the edits, I hope you can answer them.
* The label name only needs to be unique in the same file right? And because there is no _W anymore, the _E can ben changed to N335.
* What is the use of the alt labels? Is this only for people who've traveld over the road before it changes? So it stays in their system?
* Because only excisting roads are changes, only the update file needs to change? And if a new road is added, then systems.csv will also be updates probably?
I can help with these.
* Labels only need to be unique within a file. The _E can be changed, but usually won't be if it's a route split (the routes are concurrent in one direction, but not the other).
* Alt labels are used in order to prevent a user from losing credit when labels change (though sometimes it's not possible, such as renumbering of freeway exits). Many users will check their log and see that their label has changed and will update their file, and later the alt label can be removed. There is a database query that allows maintainers to check which alt-labels are being used.
* For route changes, only the update file needs to change (and sometimes, not even that; there's rules about what changes need to be included). For route additions or removals, the appropriate csv files in hwy_data/_systems will be updated. systems.csv would be updated if a new system was implemented (for example, a new country's highways).
