Closure of the Silverbridge Road between Newry and Crossmaglen has sparked outrage among businesses.
A section of the B30 closed yesterday for drainage and resurfacing.
Diversions are in place between 9am and 5pm and will be for the duration of works - eight weeks.
But those diversions will drive passing trade away from the businesses that rely heavily on it.
Vivo shop owner Josephine Murphy told Q Radio that with Christmas stock coming in this week, she wrote to the Infrastructure Minister.
She has yet to receive a response.
Ms Murphy, who's business barely survived a road closure two years ago, has placed staff on protective redundancy.
She's angry that they were not given enough notification of the closure.
A notice was placed in local newspapers last week.
Kathleen Finnegan runs a nursery and garden centre.
She told Q Radio she's "trying not to think that far ahead or about it at all."
A post office in the convenience store, a security firm, a takeaway and a civil engineer are affected by the road closure.
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