The EU funded Integrated Project APROSYS aims to increase the safety of road users. Among others, Subproject 6 (SP6) "intelligent safety systems" develop, realize and verify novel side pre-crash systems. Based on an application analysis and a system definition, we selected the sensors of a suitable side sensing system. The sensing system is based on a stereo video rig and a short-range radar subsystem. Based on an extensive simulation study, we identified the specific requirements of the side pre-crash application. As a first result, we adapted the fields of view of the sensors to the specific needs of side pre-crash sensing. As a second result of simulation we identified false alarm discrimination as a major challenge of side sensing