Elevator doors shall open and close automatically and shall comply with the following:
T = D/(1.5 ft/s) or
T = D/(457 mm/s)
T = total time in seconds
D = distance (in feet or millimeters) from a point in the lobby or corridor 60 inches (60" = 1524mm) directly in front of the farthest call button controlling that car to the centerline of its hoistway door. SeeFig. 28b.
For cars with in-car lanterns, "T " begins when the lantern is visible from the vicinity of hall call buttons and an audible signal is sounded.
521 CMR, § 28.6