a trailer - mounted crash impact attenuator is disclosed for attachment to a host vehicle , which comprises an anti - rotational attachment system having an internal support tube and a plurality of external support tubes . the internal support tube has a connector on a front end thereof for attachment to a suitable receptacle on the host vehicle , and the plurality of external support tubes each have an anti - rotation support pad on a front end thereof . at least one of the internal support tube and the plurality of external support tubes is comprised of a telescoping construction . a backup frame is disposed on a rear end of the attachment system , and a crash attenuator unit is disposed on an axle and pair of wheels for mobility . when the crash attenuator is impacted by an errant vehicle , the anti - rotational attachment system is actuated to prevent the trailer mounted crash impact attenuator from rotating relative to the host vehicle .