In this paper, we present a software tool for automotive safety engineering called AVL Safety Extensions (AVL_SE). The tool is part of a software tool framework and supports a workflow for model-based system safety engineering of HEV (hybrid electric vehicle) powertrain E/E (electrical and/or electronic) systems. We focus on AVL_SE's features which allow synchronising safety requirements in the model database and the requirements database of the software tool framework. The synchronisation mechanism enables full support for safety requirements round-trip engineering using a modelling tool and a requirements engineering tool. Our description of AVL_SE, the tool framework, the workflow and the support for safety requirements round-trip engineering is accompanied by the automotive case study of an HEV powertrain development illustrating how our approach allows coping with the vast number of requirements emerging from system safety engineering.