I disagree. Cars should be at surface levels. Going below ground or above ground is too expensive: cars (and more importantly trucks which this tunnel doesn't cover at all) are heavy and so they need expensive infrastructure. We can have tunnels and overpass in places where required, but in general cars belong at surface level.
What we should be doing is moving humans up: we should be building sky ways between buildings. Someone on foot (I'll allow wheelchairs) is not very heavy and doesn't take much space: the amount of infrastructure needed to support them is not nearly as expensive as moving cars to a different level. The skyway also allows for heating and air conditioning, something humans like.
When the distances get long we can put in a moving sidewalk if we want. However, for the most part when distances get long humans should move back to ground level and catch a bus/train.
Trucks are large: they need bigger more expensive tunnels. It isn't that we cannot do it, it is just that tunnels are expensive, and the larger you make them the more expensive they become. While a car/truck less city sounds like a great idea, it isn't practical. There are a lot of goods that need to move around somehow for a city to work. While trains or horses could be used instead, both have issues as we get to the "last mile".
Thus I'm proposing get humans off the ground level - we have the technology to make this convenient today. The cost is not very high and it solves a lot of congestion problems on the street.
What we should be doing is moving humans up: we should be building sky ways between buildings. Someone on foot (I'll allow wheelchairs) is not very heavy and doesn't take much space: the amount of infrastructure needed to support them is not nearly as expensive as moving cars to a different level. The skyway also allows for heating and air conditioning, something humans like.
When the distances get long we can put in a moving sidewalk if we want. However, for the most part when distances get long humans should move back to ground level and catch a bus/train.