Subject to section 1a, the officials in charge of constructing, improving, or repairing highways may close any highway or portion of highway that is under process of construction, improvement, or repair or upon which is located any bridge that is being constructed or repaired. A highway or portion of highway must not be closed under this act until after suitable barriers have been erected at the ends of the closed highway or portion of highway, and also at the point of intersection of the closed highway or portion of highway with other highways.