a bar placed on the edge of a path, a boat, etc. to protect people and prevent them falling over the edge 护栏；扶栏 - (North American English) (British English crash barrier)
a strong low fence or wall at the side of a road or between the two halves of a major road such as a motorway or interstate （高速公路或州际公路上的）防撞护栏，防撞墙