Door operator system, emergency release device and isolation lock mechanism for a transit vehicle door, comprising: a door operator system configured to move the transit vehicle door between open and closed positions; an emergency release device connected to the door operator system and configured to manually unlock the door operator system; and an isolation lock mechanism, comprising: a lock bracket configured to be connected to the transit vehicle door; a lock pin configured to be moved between an engaged position in which the lock pin is extended to engage the lock bracket and a disengaged position in which the lock pin is withdrawn from the lock bracket; and a linkage assembly (35, 36, 37, 38, 42, 43, 45) connected to the lock pin and configured to be actuated to move the lock pin between the engaged position and the disengaged position, wherein the linkage assembly (35, 36, 37, 38, 42, 43, 45) is connected to the emergency release device such that operation of the emergency release device actuates the linkage assembly (35, 36, 37, 38, 42, 43, 45) to move the lock pin from the engaged position to the disengaged position, and wherein the linkage assembly (35, 36, 37, 38, 42, 43, 45) is configured to be switched between an activated state in which operation of the emergency release device to unlock the door operator system actuates the linkage assembly (35, 36, 37, 38, 42, 43, 45) to move the lock pin to the disengaged position and a deactivated state in which operation of the emergency release device to unlock the door operator system does not actuate the linkage assembly (35, 36, 37, 38, 42, 43, 45) to move the lock pin. a door operator system configured to move the transit vehicle door between open and closed positions; an emergency release device connected to the door operator system and configured to manually unlock the door operator system; and an isolation lock mechanism, comprising: a lock bracket configured to be connected to the transit vehicle door; a lock pin configured to be moved between an engaged position in which the lock pin is extended to engage the lock bracket and a disengaged position in which the lock pin is withdrawn from the lock bracket; and a linkage assembly (35, 36, 37, 38, 42, 43, 45) connected to the lock pin and configured to be actuated to move the lock pin between the engaged position and the disengaged position, a lock bracket configured to be connected to the transit vehicle door; a lock pin configured to be moved between an engaged position in which the lock pin is extended to engage the lock bracket and a disengaged position in which the lock pin is withdrawn from the lock bracket; and a linkage assembly (35, 36, 37, 38, 42, 43, 45) connected to the lock pin and configured to be actuated to move the lock pin between the engaged position and the disengaged position, wherein the linkage assembly (35, 36, 37, 38, 42, 43, 45) is connected to the emergency release device such that operation of the emergency release device actuates the linkage assembly (35, 36, 37, 38, 42, 43, 45) to move the lock pin from the engaged position to the disengaged position, and wherein the linkage assembly (35, 36, 37, 38, 42, 43, 45) is configured to be switched between an activated state in which operation of the emergency release device to unlock the door operator system actuates the linkage assembly (35, 36, 37, 38, 42, 43, 45) to move the lock pin to the disengaged position and a deactivated state in which operation of the emergency release device to unlock the door operator system does not actuate the linkage assembly (35, 36, 37, 38, 42, 43, 45) to move the lock pin.