Read the Operator Manual for the truck and follow the manufacturer's instructions.
Further, please refer to OSHA 1910.178, Final Rule, Section III (Powered Industrial Truck Hazards) - "On the other hand, when a stand-up rider truck tips over, the truck operator can exit the vehicle by simply stepping backward, perpendicular to the direction of the vehicle's fall, to avoid being crushed. In this situation, the operator usually should attempt to jump clear of the vehicle, and should be trained accordingly."
Also, please refer to ANSI/ITSDF B56.1-2018 Section 5.3.22,(e) - "These trucks are designed with open operator compartments to permit easy ingress and egress. Although there is no sure way in all circumstances to avoid injury, where possible, in the event of an imminent tipover or off the dock accident, the operator should step off and away from the truck. These actions are intended to reduce the risk of serious injury or death."