The board of supervisors, at the time of the annual township meeting, upon resolution, may transfer or set aside a part or all of any funds into a special road fund, which fund must be separate and distinct from all other funds. The special road fund may not exceed the sum of five hundred thousand dollars for any one congressional township. The special road fund may be expended, at the option of the board of supervisors, for the purpose of road construction, graveling, snow removal, or surfacing.