Gully traps on highways and flyovers are cleared once every six weeks with specialised equipment 至于高速公路和天桥上的集水沟气隔，则使用特别设备每六星期清理一次。
5.
Gully traps on highways and flyovers are cleared once every six weeks by mechanical gully emptiers after midnight when traffic is light 公路和天桥上的集水沟气隔，则每六星期以机械清渠车清理一次，工作会在午夜后车辆较少时进行。
