The load carried by a motor vehicle shall not project beyond the body of the vehicle in such a manner or position as to cause or be likely to cause danger to any person on a road. It shall be carried in such position where it is not likely to strike any person with whom the vehicle may collide or is not liable to cause injury to any person by reason of any projection thereon.

Whenever a load that is being transported on a vehicle projects laterally beyond the body or wheels of the vehicle or any authorised fitting permanently attached to the vehicle, a red flag by day and a red lamp by night shall be affixed to the extreme lateral projection (if any) and the extreme rear end of such load so as to be clearly visible and give adequate warning to other road users.

Source:LTA