Some permanent changes take effect today in the short-term parking lot at Roanoke-Blacksburg Regional Airport. You will still be able to drive into the lot from either one of the two existing entrances, but you can no longer drive from side of it to the other. That’s because crews are installing a covered canopy along the walkway that goes down the middle. Construction of the canopy walkway started last August, and it is expected to be completed by March. Airport officials say there are signs to help you understand the changes.