No ordinance proposed under Section 35701 is effective with respect to any highway which is not under the exclusive jurisdiction of the local authority enacting the ordinance, or, in the case of any state highway, until the ordinance has been submitted by the governing body of the local authority to, and approved in writing by, the Department of Transportation. In submitting a proposed ordinance to the department for approval, the governing body of the local authority shall designate therein, an alternate route for the use of vehicles, which route shall remain
unrestricted by any local regulation as to weight limits or types of vehicles so long as the ordinance proposed shall remain in effect. The approval of the proposed ordinance by the Department of Transportation shall constitute an approval by it of the alternate route so designated.