ยง  131-b.  County highways and bridges. 1. A board of supervisors may,
  when satisfied that it is for the  interest  of  the  county,  lay  out,
  construct, open, alter or discontinue a county highway therein, or cause
  the  same  to  be done, and construct, repair or abandon a county bridge
  therein, or cause the same to be done when the board shall deem that the
  interest of the  county  will  be  promoted  thereby.  All  expenses  so
  incurred  shall  be a county charge, and may be financed pursuant to the
  local finance law.
2. Whenever the board of supervisors of a county  shall  determine  to
  construct  a  bridge in accordance with the foregoing provisions of this
  section, such board, on behalf of the county, and the town  board  of  a
  town  or  in  case  of a city the board of aldermen or any similar board
  exercising the functions of aldermen, on behalf of such  town  or  city,
  may  enter  into  an  agreement with the county, to the effect that such
  town or city will operate and maintain such bridge, in case  the  bridge
  is  located  wholly in a town or city. In case the bridge is constructed
  over a stream forming the boundary line between two towns or two  cities
  or  between  a  town  and  city,  then they may agree with the county to
  operate and maintain such bridge jointly, in proportion to the  assessed
  valuation of such town or city. The sum which the town or towns, city or
  cities  are obliged to pay under such an agreement is a charge upon such
  towns or cities and shall be paid as other  town  or  city  charges  are
  paid.
Structure New York Laws
111 - Payment and Apportionment of Cost Among Counties and Towns.
113 - Annual Statement of Cost.
114 - Sources and Use of County Road Fund Moneys.
115 - Preparation of Map Showing Proposed County Road System.
115-A - Abandonment of Unused Portions of Town Highways on County Road System.
115-B - Removal of Road or Part of Road From County Road System.
115-C - Notice to Municipalities Where County Roads Are Abandoned or Revert to Such Municipalities.
116 - Statement and Approval of Proposed Work.
117 - Construction and Reconstruction of County Roads.
117-A - Highways in Villages in Niagara County.
117-B - Controlled-Access Highways in Counties.
117-C - Hawking, Peddling, Vending, Sale of Goods, Wares or Merchandise; Erie County; Certain Areas.
117-D - Pedestrian Overpass to Be Designated as the "Jennifer Bolender Memorial Overpass".
118 - Acquisition by Counties of Lands for Right-of-Way and Other Purposes.
118-A - Abandoning of Parts of County Highways.
118-B - Entry Upon Lands by County Superintendent.
120 - Petition to Acquire Lands.
121 - Commissioners of Appraisal to Be Appointed.
122 - Duties of Commissioners of Appraisal.
123 - County Treasurer to Pay Awards.
125 - Land May Be Sold or Leased; Disposition of Proceeds.
127 - Payments From the County Road Fund.
129 - Maintenance and Apportionment of Cost.
130 - Bridges on County Road System.
131 - County Roads of Additional Width and Increased Cost at Expense of Village.
131-B - County Highways and Bridges.
131-C - Location and Construction of Bridges.
131-D - Construction by County of Destroyed Bridges.
131-E - Bridges Over County Lines.
131-F - Streets Outside Cities.
131-G - Regulation of Toll Rates.
131-H - Separate Highway Districts in Certain Counties.
131-J - Development of Highways and Other Improvements in Certain Counties.
133 - Machinery, Tools, Equipment, Implements, Materials and Supplies.
133-A - Rental or Hiring of County Highway Machinery, Tools or Equipment.
134 - Purchases by County Purchasing Agent.
135 - Snow Removal, and Cutting of Weeds.
135-A - Control of Snow and Ice Conditions on County Roads.
136 - Permits for Work Within the County Road Right of Way.
137 - Maintenance of Certain Highways by a County.
139 - County Liable for Injuries Caused by Defective Highways and Bridges.
139-A - Presentation of Claims for Torts; Actions Against Counties.