Basicly the 2 lane 2 way entry road is tiny compared to the airports we create. I suggest having as an upgrade to be able to build roads in the space between the tunnel entrance and the build able area. 6 new items to build: 2 lane road entrance and exit, 4 lane road entrance and exit, and 6 lane road entrance and exit.
Could it just be an upgrade like when you upgrade stands? So you click and get maybe 2 the 4 then 6 lanes?
This would be a good unlock feature. Add road entrance from off map to increase roadside capacity.
This proposal looks like this: proposing a freeway off the map, choosing the type of driveways, and where to place these entrances.