Tonight I went to the Terrace Tunnel walk-through. We moved here in 1978, which was the year the tunnel opened. They had a walk through then too, but we were either too late to go on it, or missed it for some other reason.
As an Aro Valley inhabitant, I was always a little sad I'd missed the original walk-through. So I was really pleased the project people had invited everyone to walk through it again. They called it a once-in-a-lifetime-opportunity, which is what they called the other one too. I hope they do it again sometime (even if it takes 30+ years), as it's a lovely way to feel some kind of relationship with what is otherwise just scenery from a road that requires you to roll your windows up. And given the damage done to the area by roading, I think that's the least they can do.
As it turned out, the volunteers and project people were really lovely, the weather cooperated, and L managed to not flake out completely despite it being very late. Many thanks to the people who answered our questions. Apparently the Deluge Zones are so you can tell the emergency services which section of the tunnel you are in. And the traffic controllers can see where you are with their cameras. I can only assume these features were prompted by the experience of fires in tunnels in Switzerland, where some people died because no one could tell where in the tunnel they were. In addition, the massive turbines on the roof are there to push exhaust fumes along (if the air quality is measured as bad enough) and to move smoke in the event of a fire. This is a good thing as apparently the smoke is one of the major dangers of tunnel fires. They also have shiny new hose reels and hydrants at regular intervals along the walls and a hefty-looking sprinkler system which will make whatever deluge zone has been activated very wet indeed. I assume the blank panels will light up with information about distance to either end at some point in the future. They've also added a noise strip to the double yellow lines, and some flexible poles to attempt to convince drivers to avoid oncoming traffic.
One point to note, the narrow footpath on the western side has been removed to fit the water for the hydrants in. This causes me mild concern, but I suspect walking along the side of the tunnel will only be necessary in conditions in which most of the traffic has slowed down or stopped anyway.