The commissioner and the selectmen of any town, or any other officer thereof having charge of the highways therein, may enter into an agreement, in writing, whereby a designated section of a state highway, other than a limited access highway, shall be maintained in whole or in part by such town, provided the parties may agree on an amount per mile which the town shall be reimbursed by the commissioner for such maintenance. The agreement shall describe the sections to be so maintained, the type of maintenance and the basis for reimbursement agreed upon, and a copy thereof shall be recorded in the office of the town clerk of the town in which the road lies within twenty days after the date of execution of such agreement. Such agreement shall operate to transfer liability for failure to discharge any statutory duty of the commissioner.