Firstly, building another highway UNDER the 410 would be a geotechnical and logistical nightmare. Try to think about all the buried services and such that would be cut and need replacement. Such a project could disrupt and make traffic much worse for decades. More than that, it would be a construction nightmare for anyone or any business along the route the whole time.
Tying in a tunnel with the above lanes would require much much larger interchanges where there were connections. This would require taking land, much of it in use, away from surrounding homes, businesses and industry. Remember this mega-farce would be cut right through a dense cityscape.
A many kilometres long tunnel would be a hazard when any accident happened in it. If it is meant to be a super-express, then exits would have to be widely spaced. Have fun sitting in a 14 km backup for four hours, underground.
But here is the real thing. Induced traffic demand is, at this point, well understood. Although obviously not by DoFo. No matter how many lanes you add to the 401, be they beside above under or bypassing the existing lanes, this can NEVER reduce congestion. That never works. That never has worked, which if you drive, you must have actually noticed. No highway expansion in our history has not made traffic worse. It is inevitable. DoFo, in a spectacular display of ignorant stupidity, is just showing us that he doesn’t know anything about transportation planning, or doesn’t care (which may be more likely) and is also not capable of listening to his own experts.
And OMG the cost. Based on the Big Dig (Boston) a 401 tunnel, if it were ever completed, would cost something like $29 billion. But it almost certainly would not be completed because the project would take so long and be so problematic, that a subsequent government would certainly cancel the folly. But in the mean time I suppose, it would be a giant quid pro quo cash-cow for OPC donors.
And here it the real bugger of the matter. Even if the cost did not skyrocket above my estimate, that amount of investment in transit around Toronto WOULD improve traffic congestion significantly.
And as every sensible person looks at this delusional fantasy bullshit and says, “what the fuck,” there are a legion of chair-leg chewing gullible short-sighted ignorant deplorables, sitting in traffic, shouting the old lie, “Hell ya! Just one more lane will fix it.”