The state transportation engineer shall provide uniform standard specifications for all lumber and timber products used in the construction of the state highways of the state of Kansas, and the county engineers of the state of Kansas shall provide uniform standard specifications for purchase of lumber and timber products for all county or township highways, bridges and culverts, and the specifications of all county engineers shall be clear and definite with reference to grade, quality, size, species and treatments required, and the same specifications shall be submitted to all bidders, and specifications for all classes of lumber and timber products shall be clear and nonconflicting: Provided, A county engineer may adopt the uniform standards and specifications of the state transportation engineer as the uniform standard specifications for his or her county.