Abstract: An apparatus for conducting impact events for use in conjunction with a hzontal accelerator includes a base having tracks attached to the top thereof; a seat slidably attached to the tracks, the seat capable of moving independently of the base and along the tracks, the seat for positioning a test dummy before and during an impact event; a barrier positioned and arranged adjacent one end of the base for impacting the test dummy, the barrier having load cells for generating signals in response to the impact between the test dummy and the barrier; an attenuator for impacting the seat and accelerating the seat up to the velocity of the base when the base is accelerated by the horizontal accelerator; and an anti-reverse mechanism for retaining the seat after the seat is accelerated up to the velocity of the horizontal accelerator. In operation, a test dummy is positioned on the seat and secured, if desired. The seat is slidably positioned on the base the desired distance from the barrier.