2015 New York Laws
VAT - Vehicle & Traffic
Title 8 - RESPECTIVE POWERS OF STATE AND LOCAL AUTHORITIES
Article 40 - (1650 - 1652-B) REGULATION OF TRAFFIC BY COUNTY SUPERINTENDENT OF HIGHWAYS
1652-A - Traffic signs, signals and marking on highways, roads and streets.

 1652-a. Traffic  signs,  signals  and marking on highways, roads and
  streets. The county superintendent of highways of a county,  except  the
  county  of  Suffolk,  having a functioning traffic engineering unit may,
  when authorized by the county governing board, have  the  responsibility
  and  authority  for the installation, removal and maintenance of traffic
  signs, signals and markings on, and provide traffic engineering services
  in relation to any highway, road  or  street  within  a  city,  town  or
  village  within  such  county,  except  state highways maintained by the
  state, providing the  governing  body  of  the  city,  town  or  village
  consents thereto by written agreement with the county governing board as
  to  the  extent  of  the  authority  and  responsibility  of  the county
  superintendent of highways  and  any  apportionment  of  costs  for  the
  installation, removal and maintenance of the signs, signals and markings
  and  traffic  engineering  services.  The  power  granted  to the county
  superintendent of highways by this section shall in no way diminish  any
  power  over  roads granted to counties or county highway superintendents
  but shall be in addition to any such powers.