Admission to the Research Center during ``off duty'' hours shall be restricted to the main arteries and any deviation therefrom by individuals shall be limited to authorized individuals who may be required to sign a register and display identification documents when requested by a guard or other authorized individuals. ``Off duty'' hours will be posted at the Research Center. Admission during ``duty'' hours when the Center is closed to the public in emergency situations will be limited to authorized individuals who may be required to sign a register and display identification documents when requested by a guard or other authorized individual.