N.Y. Comp. Codes R. & Regs. tit. 16, § 255.181 – Distribution line valves.

(a) Each high pressure distribution system must have valves spaced so as to reduce the time to shut down a section of main in an emergency. The valve spacing is determined by the operating pressure, the size of the mains, and the local physical conditions as well as the number and type of consumers that might be affected by a shutdown.
(b) Each regulator station controlling the flow or pressure of gas in a distribution system must have a valve installed on the inlet piping at a distance from the regulator station sufficient to permit the operation of the valve during an emergency.
1. (1) Such distance must be at least 50 feet (15.2 meters) but no more than 1,000 feet (304.8 meters) from the regulator.
2. (2) Under unique circumstances which make it impractical to locate the valve at least 50 feet (15.2 meters) from the regulator, a lesser, approved spacing may be used.
(c) Except for single feed systems, regulator stations reducing the pressure from pounds to pounds must also have an emergency valve installed on the station's outlet piping in compliance with paragraphs (b)(1) and (2) of this section.
(d) Each valve on a main installed for operating or emergency purposes must:
1. (1) be placed in a readily accessible location so as to facilitate its operation in an emergency;
2. (2) have an operating stem or mechanism that is readily accessible; and
3. (3) if the valve is installed in a buried box or enclosure, be installed so as to avoid transmitting external loads to the main.
(e) Each station bypass valve or valve that separates systems operating at different pressures must be identified to prevent unauthorized or inadvertent operation, or be equipped with a device designed to prevent unauthorized operation.