What does this mean ? alt periods of physical placement are granted at reasonable times upon reasonable notice

Your son's custody placement order means he must provide advance 24 hours notice of his request to have his placement, and the mother has reasonable veto power over the request. If she denies him all the time or insists he can only visit if she is present, she is not being reasonable; he needs to file a motion for contempt or motion to enforce his physical placement; the court can put an order in with set dates and times if mother is going to constantly interfere.

The police are very reluctant to get involved in a custody case, and are very unlikely to do anything to assist your son's particular situation. If your son provides reasonable notice, and the child's mother consistently denies reasonable requests for placement, your son can go back to court and request a more specific order delineating specific times he will have placement. He should be sure to document each request for placement, and each denial, and be prepared to provide testimony and copies of any relevant documentation.