Many northern (and some southern) cities have a skyway system which connects pedestrians on the second floor. Out of the weather, comfortable temperature year round. Let the cars have the icy slippery roads at ground level, no need for a sidewalk near the street. Once you leave your car head to second floor and go where you want to be. The second floor rents are the highest because that is where people are.

Building tunnels is expensive. Building bridges for cars is expensive, but a bridge that only needs to handle humans is much cheaper a 500kg fatso is much lighter than a 500kg fatso in a 4000kg SUV.

i agree with you generally. let's put express lanes underground (for both cars and trains), since they're prioritizing getting places quickly over easy access.

but to be fair, that's more (sometimes much more) expensive. not only because of the digging required to put the lanes/tracks underground, but also the extra things like ventilation systems and pedestrian exits/corridors.

I recall Toronto had a labyrinth of passage ways under ground, with shops etc. It connected to the subway and it was very convenient. Guess they built under ground due to the weather?