I travel through these tunnels from intermittently. They aren't well marked, there is no predicting them. They don't lead through mountains; I tend to go over those. The tunnels are random. They can be brief, but you can always hold your breath through them if you choose. They are not dark, but they block out the sun. I try to entertain myself with the flickering lights while passing under their arching solid walls. No matter how slow I travel there will always be another tunnel to pass through.
That doesn't stop me from traveling.
