Doesn’t even have to be solely trains, but a few lanes of busses would help with shorter/End of Line trips as well.
Though this is worth noting that ventilation concerns with tunnels are always a nightmare (one of the reasons there aren’t tons of tunnels). Its now turning into an issue where roads cross our 400 series highways, and one of the reasons they’re often bridges. As the highway reaches ~4lanes each way, they need to install ventilation of some kind, which has caused problems and forced design adjustments. Look at Barrie where they have a few roads running under the 400. Now that they’re trying to widen to 8 lanes, all those crossings are extending into “tunnel” category and have additional requirements. They’ve been forced to split the highway with an open air section in the middle over those roads in order to ensure proper airflow. This means more land acquisition and higher pricing to build.
Ventilation still a problem with just electric trains with metal rolling stock?
I could be off, but I seem to remember that the requirements for ventilation are less if there is no combustion engine + exhaust fumes present. I’ll see if if I can dig up the actual design standards.
Also I wonder how does the train movement affect ventilation. I recall the mountain train tunnels in Italy. Since the tunnels are just wide enough, the trains act as pistons, pushing and pulling air in and out of the tunnels. I recall experiencing pretty strong wind coming out of the tunnel prior to the train emerging out of it. I wonder if this is enough to circulate enough air. I’m not expecting an answer, just wanted to share this shower thought. 😄
It is an issue, but an ICE burns far more fuel than a human. (food is fuel that the body burns!) That means if your have ICE engines in a tunnel you need a lot more air to get rid of the CO2 (ideally no other pollutants - though I wouldn’t bet on this) and get enough O2 there for everything to burn. If we only run electric trains we still need some air for the people to breath, but much less as they are breathing much less
