I forget about turn restrictions, that's a good idea. It seems like a good routing algorithm should only need the motor_vehicle=no tag on the barrier itself, but I'm not opposed to also tagging the section of way if that will help. As for the safety of cyclists, there is room for riding to the side of the barriers, as they don't fill the whole width of the street. I'm sorry, my picture doesn't show this very well... it also doesn't show the large rocks placed on the grass to prevent creative motorists from attempting the same thing. Incidentally, this strange situation is a compromise between the resident's concerns about increased traffic from a large business and the concerns about emergency vehicle access. It's unusual even for that area.

Thank you for the suggestions, I will implement them soon unless you prefer to do it yourself.