If this tunnel is working using the "skateboard" concept then you'll need a certain number of those on hand, plus some kind of turn-around system to get people

If this tunnel is working using the "skateboard" concept then you'll need a certain number of those on hand, plus some kind of turn-around system to get people on and off of them. Unless you had a massive staging and unloading area, 12 vehicles per minute is completely impossible. I think your low-end estimate is much more reasonable. I also think if people are manually driving cars it's only a matter of months until there's a spectacular crash in the tunnel because some idiot thought they could drive up the wall at speed or something.