The Secretary of Transportation may grant to every railroad corporation whose primary business is the transportation of passengers the rights-of-way for the location, construction, and maintenance of its necessary works and for every necessary adjunct thereto over any portion of highway owned by the State of California which is not otherwise disposed of or in use, not in any case exceeding in length or width that which is necessary for the construction of works and adjuncts, or for the protection thereof, and in no case to exceed 200 feet in width.