There are thousands of cars and trucks idling on I-70 every weekend for hours. Can’t be good for emissions. There’s also little room to expand highways in the mountains without moving many tons of rock.
This isn’t an easy problem, and that’s just one little part of it. Being 30 years behind on infrastructure doesn’t help either.
I don’t know what happened, but my previous post was meant for your #5.
Modern vehicles emit such clean emissions that a person can’t even gas themselves to death in the garage anymore. They can idle all they want.