a system is provided for absorbing energy from impacts to a vehicle , the system comprising : a blow molded energy absorbing member . the member including first and second opposing walls , at least one rib or a pair of ribs disposed between said first and second opposing walls , the rib comprising the first and second opposing walls dented toward other wall with top end part either welded or separated with specified interval . in one embodiment , the energy absorbing member is formed of thermoplastics composed of a polyolefin based resin and 50 to 75 % weight of an amorphous resin .