The light at the end of the tunnel is a truck

From the time we crossed back into Serbia from Romania to Mostar in Bosnia we have had to deal with Tunnels. They started off like a bit of a novelty along the Danube but as we entered Bosnia at Visegrad and headed to Sarajevo they became pretty hairy and exhausting.
The vast majority are not lit at all and can be long enough that they are pitch black inside. A series of twenty or so tunnels met us after Visegrad varing in length from 50 to 700m or so. There are quite a few heavy trucks using the road in this section that inside the tunnel sound like the death star looming up behind you. We wore reflective vests and had head torches facing back so we could be seen but it still was extremely nerve wracking. We also used a hand held torch to see the road ahead. We rode into one tunnel without our torches and found we couldnt balance on the bikes properly without something to orientate ourselves with visually. We were riding crookedly and nearly falling over and scraping the side wall. Scary! However, once we whipped out our  light and directed at the line on the side it was smooth sailing.