I doubt it would affect pollution significantly. It's not like both ends of the tunnel aren't open to the air. It would definitely locally displace it so it's not distributed across the above ground length of the road, but the same amount more or less (minus whatever adheres to walls) is still coming out of either end.

Underground tunnels also have the danger of fires rapidly spiraling out of control and in the past have killed dozens of people, and that was before electric cars became common. I would not want to be in a tunnel when a Tesla's battery explodes.

I'm not saying this has no advantages, but for the trouble and cost it seems like a train would be better.

[–] pascal@lemm.ee 3 points 1 year ago

I think it's better from a polluting point.

Nothing underground generates oxygen, but moving the roads from above to underground gives more "it's free real estate" to grow grass and trees, like in the second photo, which generates oxygen and stores carbon. It's not the best thing like suppressing the cars all together, but it's better than the first picture.

[–] Resistentialism@lemmy.world 2 points 1 year ago

Yeah, I completely forgot about the whole fire thing.

When yku say it like that. It makes more sense. It's a shame we don't have super efficient ways to convert exhaust gasses into healthier gasses. But yeah, if it's just a short tunnel, the entrance and exits would just not funnel it right. I wonder if really long tunnels would be better. Maybe being able to use the entrances with a system to input clean air and force the exhaust through vents.

And I wonder if those fire suppression systems that starve the fires of oxygen could be something that could be useful? But that'd require automated doors to seal the tunnel, and then if someone is trapped on there, the fire is the last of their issue. Unless there were refugee points that also seal, but then you've gotta make sure everyone's in them. I wonder if some form of scanner could be used to allow humans in. But then there's that thing where a fire has been starved, but then gets a sudden burst of oxygen and it becomes explosive. I forgot what it's called. I'm sure someone actually smart could brainstorm it better.