Method for operating a safety system of a motor vehicle and motor vehicle

Method for operating a safety system (3) of a first motor vehicle (1, 2) for collision avoidance and/or collision consequence mitigation, wherein at least one collision parameter describing a possible collision with a second motor vehicle (2, 1) is determined by evaluation of environmental data about the environment of the own motor vehicle (1, 2) and ego data about the own motor vehicle (1, 2), and upon fulfillment of at least one collision criterion evaluating the collision parameter, at least one further vehicle system is activated to carry out a measure, wherein at least one collision parameter related to an underride accident is determined as a function of a pitch angle of the second motor vehicle (2, 1) transmitted by the second motor vehicle (2, 1) via vehicle-to-vehicle communication and is evaluated to trigger a measure aimed at preventing and/or mitigating the consequences of an underride accident upon fulfillment of a triggering criterion.