My procedure for tunnels - I generally have a pair of dark sunglasses on, these stay on 'till I'm just inside the tunnel. My halogen light is pointing up onto the roof and just slightly to the right, plenty of light to see with. I also switch on my nav lights, these give enough coloured light on the tunnel wall for gauging where I am in relation to them, and also ( I presume ) give anybody coming towards me a better indication of where my boat is in relation to the tunnel.
Just out of interest, when going through Braunston tunnel last year and on my own, I turned off the tunnel light just leaving the nav lights on, that was enough light to see by.
Now, to ultra bright LED lights, a few years ago, the road I was using to cycle to work had roadworks for 6 months over the winter period. I found another route I could use which was mainly off road. I bought one of those fantastic LED lights and was happy cycling on the rough track in the dark, the light showing me the way. After about 5 miles, the track finished and I was back on a very quiet road. A good distance away from me a car was coming towards me, the driver had dipped his lights and he flashed me to do the same. It was at that point I realised how much of a problem my bike light could cause. I then lowered the light, and thus the beam, to point down.
My point? I'm sure many of these LED tunnel light users are unaware of the problems they cause, but as more people make them aware, I would hope, like me, they would take remedial action - but maybe I'm a dreamer!!