Quite easily!......With a one way system. The current tunnel in/out road would be the entrance road and the old road (now a dead end near RSS) as the exit road. Yes, it may have required another small tunnel but the lack of foresight over this issue speaks volumes about how the airport has been developed and the current mess is the legacy we have to live with
Errr then what? Do you think that the old approach road via Eaton Green Road and its residential housing would be a better solution as an exit? That's an extra 4 roundabouts on narrow roads that are congested just to get back to where the existing airport road hits the A505. Also you would be looking at a tunnel at least twice as long as the exiting one.