In a large metro with an extant, functional, mass transit system, sure. But do this in a cold place with no existing mass transit, and all you'll do is kill off downtown businesses and reduce property values to 0.

This experiment was kind of done in Buffalo in the 70s. They blocked off large swathes of downtown to build the above ground section of metro rail. This encouraged business to close downtown locations and move to suburban malls. That kind of retail never came back to downtown in the roughly 1 decade after completion of the metro. So you had a mass transit system that went effectively from nowhere to nowhere, and managed to kill the downtown retail corridor.