Out of interest, how much real estate would it actually free up? I assume you still need roads for emergency services, delivery trucks, construction vehicles, e

Out of interest, how much real estate would it actually free up? I assume you still need roads for emergency services, delivery trucks, construction vehicles, etc... Maybe the number of lanes can be reduced, but that wouldn't exactly free up any sizeable amount of real estate that could be used for more housing, or would it?