Any county shall be entitled to receive state aid and to expend state aid monies in conjunction with monies furnished by said county on state aid roads in such county on projects approved for construction in such county, provided:
The state aid system in such county has been designated and approved as herein provided.
The county has employed a county engineer to act for and on behalf of the county as a whole, who shall be a registered professional engineer, and such other competent technical assistants as may from time to time be deemed necessary by the board of supervisors of said county.
An annual program shall have been filed by the county engineer with the division of state aid road construction and approved by the State Aid Engineer, and in accordance with the uniform design standards and specifications set up by the State Aid Engineer; such program may be modified or revised in whole or in part by the State Aid Engineer, with the agreement of the county involved.
Such county has complied with all rules and regulations promulgated by the State Aid Engineer.