As GLC mentioned, gates for winter closures are hardly unique to I-90.
If they do close the highway, it will be obvious where you have to get off - they will direct all traffic onto an off ramp, just like they would if the highway was closed for crash or construction.
You'll also notice that the closure points are at larger cities that have traveler services like multiple gas stations and motels, so you would have a place to go if the roads are closed.
