The department of transportation is directed to enforce compliance with this part; provided, that the commissioner of transportation or the commissioner's designee shall have the power and the duty to prescribe and authorize a vertical or side clearance less than the minimum required in this part in particular cases when, on application therefor, after notice posted at the railroad station nearest the place affected, and after hearing if requested, the department of transportation may find a reasonable necessity or justification for such action; and provided further, that this part shall not apply to temporary forms, supports, falsework, bracing, etc., used only during and in the construction or repair of any underpass or overpass for a street, road or highway.