In 1996, about 200 metres after I entered the Homer Tunnel in New Zealand, the lights went dark. The A behind me was fitted with original style 6v globes in their lights, meaning you had to strike a match to see if they were going. I only had a little light shining past me onto the walls of the tunnel and my own shadow to guide me. The next kilometre or so was slow and I was nervous someone travelling faster would rear end the two of us.
For thse who don't know what the Homer Tunnel is,
https://en.wikipedia.org/wiki/Homer_Tunnel