Shikoku Pilgrimage - walking in tunnels

I'm planning on walking the Shikoku pilgrimage this year, and my research shows that there are quite a few sections where I have to walk through tunnels. They don't have dedicated "lane" for pedestrians, just a small shoulder lane! Looks very dangerous.

Has anyone here walked these tunnels? Any advice?

I've walked a couple. Carry a flashlight so the oncoming traffic can see you. Try not to bump into the walls as your clothes will turn black from the soot. It's not pleasant. Depending where you are, in some places there is an old road that is closed off that goes around the outside instead of through the tunnel. If you see one of these you might try it although not all go all the way to the other end of the tunnel (as I found out) and you might have to backtrack. Cars are supposed to watch out for the walkers and there are signs telling them to do so where there aren't pedestrian side lanes, but it can still be unnerving.