If a person doesn't have the proper proximity card, that person will be prevented from entering a server room or other protected room. Security guards can also prevent people from accessing unauthorized areas. However, bollards (short vertical posts) probably wouldn't stop a person, besides they aren't normally installed in front of a server room entrance. A barricade might stop a person, but again, would be out of place! CCTV video surveillance is a detective control, but not a preventive control. 802.1X deals with authentication, not with physical security.