100 lanes sounds like a massive exaggeration but is actually undercutting it lol. It's insane how space and energy inefficient it is to transport that many people in individual cars.
The yamenote line transports 5 million people a day
The Katy Freeway transports 219 000 cars. Let's say that's 400 000 people. (pretty generous I think, most cars are just one guy driving to work)
You would need 5 million / 400 000 = 12.5 Katy freeways.
That would be 12.5*26 lanes =325 lanes!