WTBhotia raises what could be a good idea, not the ferry idea but......
Why not ban trucks and vans during peak morning/evening hours, only allowing them to operate before the peak hour rush periods, or after...Backed up with very stiff fines should they ignore the curfew, say $1500 on the spot fine.... To be honest it is they who choke up most of the traffic, because if you drive through the same tunnels on a Sunday, with just private car traffic, no vans and trucks around, it flows quite well. Quite a contrast compared to during the week, when there are 5 vans/trucks for every private car.....
I think that would make a HUGE difference if you got those diesel vehicles off the roads during those times... Another thing would be to get the diesel vans off the road, replacing them with dedicated LPG injected versions, like they did with taxi's here, which were previously diesel..
It all helps if lowering roadside pollution during peak times is the aim of the game.