New feature: cost of blocking particular routes

[Rob217]

How much does blocking a particular route make completing tickets more difficult? Are there any routes that when blocked would have a bigger impact than others?

Could quantify this by calculating how much the average shortest (or average of the n shortest) path lengths increases when you block a route.

Blocking a high density route may not increase the path lengths that much if there are other available routes nearby with similar path lengths.

Blocking a lower density route surrounded by long routes (e.g. LA to Phoenix) might have a bigger impact if, in forcing players to go around, the average path length increases a lot.