Standup high lift trucks have an open operator compartment designed to allow for easy egress from the truck in the event of an off-dock, off-trailer, or tip-over accident. The open compartment design also protects the operator during nontip-over collision accidents, provided the operator maintains him or herself within the compartment before impact. However, it has been suggested that an additional rear operator guard would better protect operators during nontip-over collision accidents. This study aimed to investigate operator injury potential and kinematics during off-dock and off-trailer accidents where the presence of a rear operator guard prevents the operator from exiting the truck and to evaluate the potential for an operator to restrain him or herself within the operator compartment of a standup lift truck during an off-dock or off-trailer accident. An instrumented anthropomorphic test device (ATD) was subjected to a series of off-dock accidents and a single off-trailer accident utilizing three different standup lift trucks. The kinematics and loads experienced by the ATD were quantified and correlated to human injury potential. Additionally, this study examined the potential for a rear operator guard to impede operator egress during an off-dock or off-trailer accident. Testing demonstrated the potential for serious or greater injury to an operator subjected to an off-dock or off-trailer accident. The authors conclude that a rear guard would negatively impact the overall safety of a standup lift truck in most working environments.