The board of township supervisors shall order the expenditure of all road taxes paid into the township treasury in the improvement of the highways under such regulations as it may deem most expedient for the public interests, and for this purpose, shall issue a warrant upon the road funds of the township upon the certificate of the township overseer that such work has been performed satisfactorily; provided, however, that not over fifty percent of the township road and bridge fund, collected within each tax year may be expended upon highways which are a part of a state or county highway system as designated under the provisions of section 24-01-02, 24-01-05, or 24-05-16, unless such expenditure is specifically authorized by resolution adopted by a majority of the electors of the township present and voting at any special or annual township meeting. This limitation also applies to any special road fund as set up under section 57-15-19.2.