The good thing about the green and orange line at North Station is that they use the same platform so you can just take whichever shows up first. That's what I used to do going back to Longwood to get my car at the Simmons garage after Bruins/Celtics games when I parked there for work. If the green came first, I'd take it to Longwood and if the orange came first, I'd take it to Ruggles.