No taxicab shall be operated or allowed to be operated unless it conforms to the following requirements: The vehicle shall be either of the built-for-the-purpose, or of the closed or sedan type, and shall be equipped with at least four doors. Passenger doors must be so constructed that they will remain securely fastened during normal operation, but may be readily opened by a passenger in case of emergency. The vehicle shall be constructed and maintained so as to provide for the safety of the travelling public, and continuous operation with minimum noise and vibration. It shall be structurally sound as to all its parts, and shall not have missing, broken, or cracked fenders or bumpers or glass. The vehicle shall be painted to give reasonable protection to its surface, and in a color scheme approved by the Director as set forth in Section 20-153 of this Code. The vehicle shall be equipped with an engine adequate to enable it to operate effectively and efficiently. The vehicle shall be equipped with a jack and safe tires, including a spare tire, with sufficient tread in accordance with the State of Maryland Motor Vehicle Administration vehicle inspection standards. In no case shall the required tires have a tread depth of less than three thirty-seconds of an inch. The vehicle shall have operating windshield wipers and windshield washer equipment. The vehicle shall be equipped with approved safety glass in the windshield and all windows. The center partition, if any, between the driver's compartment and the passenger's compartment shall be of this type of glass or plastic. The vehicle shall have one set of operating seat belts for each passenger and the driver. The vehicle shall be equipped with a standard speedometer, properly installed, maintained in good working order and exposed to view. No vehicle shall be operated in service if the speedometer is out of repair or disconnected. The vehicle shall be equipped with a heater sufficient to heat the interior adequately in cold weather and air conditioning sufficient to cool the interior adequately during hot weather. The vehicle shall not be equipped with any lights or signal devices except as allowed by the Motor Vehicle Laws for the State of Maryland, and as approved by the Director. The vehicle shall not be equipped with shades or curtains which can be manipulated in such a way as to shield the occupants or the driver from observation, or obstruct the rear view window. The vehicle shall be equipped with a frame for the proper display of the certificate and the license shall face the passengers and be so located as to be at all times in plain view of such passenger(s). The card frame shall be subject to approval of the Director. With exception of a "kick" strip not exceeding seven inches in height at the bottom of doors, no upholstery covering or interior lining shall be permitted in any licensed taxicab unless such upholstery or lining is made of leather or similar nonabsorbent, washable material. The rear cushion shall be removable. Floor mats shall be required in all licensed taxicabs and shall be made of rubber, leather, or metal chain, or a similar, nonabsorbent, washable material and shall be easily removable. The vehicle shall be kept clean and in a sanitary condition. At least once every seven days, the exterior shall be washed and the interior shall be cleaned thoroughly with a suitable antiseptic solution. Except as provided in Sec. 20-145(a)(16), no taxicab shall continue in service which is: as of January 1, 2018, more than eight (8) model years old unless an annual waiver is granted by the Director. An annual waiver shall be based upon a written finding that such vehicle has passed an inspection which ensures that such vehicle is safe and in good operating condition. as of January 1, 2019, more than seven (7) model years old unless an annual waiver is granted by the Director. An annual waiver shall be based upon a written finding that such vehicle has passed an inspection which ensures that such vehicle is safe and in good operating condition. as of January 1, 2020, more than six (6) model years old unless an annual waiver is granted by the Director. An annual waiver shall be based upon a written finding that such vehicle has passed an inspection which ensures that such vehicle is safe and in good operating condition. No taxicab which is a Qualified Hybrid Vehicle or Plug-in Electric Drive Vehicle, or accessible taxi shall continue in service which is: as of January 1, 2018, more than nine (9) model years old unless an annual waiver is granted by the Director. An annual waiver shall be based upon a written finding that such vehicle has passed an inspection which ensures that such vehicle is safe and in good operating condition. as of January 1, 2019, more than eight (8) model years old unless an annual waiver is granted by the Director. An annual waiver shall be based upon a written finding that such vehicle has passed an inspection which ensures that such vehicle is safe and in good operating condition. as of January 1, 2020, more than seven (7) model years old, unless an annual waiver is granted by the Director. An annual waiver shall be based upon a written finding that such vehicle has passed an inspection which ensures that such vehicle is safe and in good operating condition. All taxicabs shall be equipped with flashing emergency lights approved by the Director. Each taxicab shall have a medallion issued by the Director displayed on the driver side front panel and rear trunk for that taxicab.