N.Y. Comp. Codes R. & Regs. tit. 21, § 1050.9 – Restricted areas and activities.

(a) No person, except as specifically authorized by the authority, shall enter or attempt to enter into any area not open to the public, including but not limited to train operator's cabs, conductor's cabs, bus operator's seat location, station booths, closed-off areas, mechanical or equipment rooms, concession stands, storage areas, interior rooms, catwalks, emergency stairways (except in cases of an emergency), tracks, roadbeds, tunnels, plants, shops, barns, train yards, garages, depots or any area marked with a sign restricting access or indicating a dangerous environment.
(b) No vehicle, except as specifically authorized, may be parked on authority property.
(c) Photography, filming or video recording in any facility or conveyance is permitted except that ancillary equipment such as lights, reflectors or tripods may not be used. Members of the press holding valid identification issued by the New York City Police Department are hereby authorized to use necessary ancillary equipment. All photographic activity must be conducted in accordance with the provisions of this Part.
(d) No person may ride on the roof, platform between subway cars or on any other area outside any subway car or bus or other conveyance operated by the authority. No person may use the end doors of a subway car to pass from one subway car to another except in an emergency or when directed to do so by an authority conductor or a police officer.
(e) No person shall extend their hand, arm, leg, head or other part of their person, or extend any item, article or other substance outside of the window or door of a subway car, bus or other conveyance operated by the authority.
(f) No person shall enter or leave a subway car, bus or other conveyance operated by the authority except through the entrances and exits provided for that purpose.
(g) No person may carry on or bring to any facility or conveyance any wheeled cart greater than 30 inches in either length or width, including but not limited to shopping or grocery store carts or baskets, but excluding any stroller which is, at the time it is on or in the facility or conveyance, being utilized for children; or any item that:
1. (1) is so long as to extend outside the window or door of a subway car, bus or other conveyance;
2. (2) constitutes a hazard to the operation of the authority, interferes with passenger traffic, or impedes service; or
3. (3) constitutes a danger or hazard to other persons.
  Nothing contained in this section shall apply to the use of wheelchairs, crutches, canes or other physical assistance devices.
  (h)
4. (1) Except as otherwise provided in paragraph (2) of this subdivision, no person may bring any animal on or into any conveyance or facility unless enclosed in a container and carried in a manner which would not annoy other passengers.
5. (2) Paragraph (1) of this subdivision does not apply to working dogs for law enforcement agencies, to service animals or to animals which are being trained as service animals and are accompanying persons with disabilities, or to animals which are being trained as service animals by a professional trainer. All service animals and animals being trained as service animals must be harnessed or leashed.
6. (3) Upon request by a police officer or designated employee of the authority or the MTA, a trainer must display proof of affiliation with a professional training school and that the animal is a licensed service animal or an animal being trained as a service animal.