From: Utopia Planitia Fleet Yards
In fact, maybe a better way to do it, implement something called Air Interdiction where, each turn, friendly hexes in the range of enemy bombers, and not covered by friendly fighters can have their rails damaged.
This way, it will reduce the:
. ability to rail move land units
. ability to supply land units
Something similar to port supply interdiction in other words.
Chancellor Gorkon to Captain James T. Kirk:
You don't trust me, do you? I don't blame you. If there is to be a brave new world, our generation is going to have the hardest time living in it.