The state highway commissioner, subject to the approval of the state administrative board and highway advisory board, is hereby authorized and directed to lay out and establish trunk line highways and other highways as are necessary to, upon or through state parks or other state property, and to build connections between state trunk lines and highways, running to, upon or through state parks and other state property: Provided, That such highways, if and when laid out and established, shall be a part of the total mileage authorized for such year.

     The state highway commissioner is further authorized to maintain and improve trunk lines or other highways traversing or upon state parks or other state property, and the connecting trunk lines with the above highways in the same manner as state trunk line highways are required by law to be maintained and improved: Provided, That no such trunk line highways or other highways be laid out and constructed, maintained and improved on any property owned by the Michigan state board of agriculture or the regents of the university of Michigan, unless the Michigan state board of agriculture or the regents of the university of Michigan, as the case may be, by resolution approved by 2/3 of its members respectively gives consent to that effect.