Anything herein contained to the contrary notwithstanding, all persons in or upon vehicular crossings must at all times comply with any lawful order, signal or direction, by voice or hand, of any employee of the Triborough Bridge and Tunnel Authority, properly identified, or any member of the New York City police force. When traffic is controlled by signs, or mechanical or electrical signals, such signs and signals shall be obeyed unless an employee of the Triborough Bridge and Tunnel Authority, properly identified, or a New York City police officer, directs otherwise.