N.Y. High. Law § 42-A
Notwithstanding the provisions of section one hundred four of this chapter, whenever in the maintenance or repair of a state highway, it is determined by the commissioner that it is necessary to provide for a temporary detour over alternate roads, streets, highways or routes, the commissioner shall have the power and authority to establish such temporary detour over alternate roads, streets, highways or routes as he deems necessary and proper for the protection of the traveling public with the posting of conspicuous signs, or use of flagmen, or a combination thereof, indicating such temporary detour. Such temporary detour shall be adequate to prevent unreasonable delay in the movement of traffic on said state highway. As used herein "temporary detour" shall be a detour of an anticipated duration not to exceed two weeks.
N.Y. High. Law § 42-A