Software product line engineering is a widely used approach to plan and manage reuse of software. When safety critical products are developed, achieving functional safety standard compliance must be shown. The requirements stated in the functional safety standards also apply when safety critical products are developed in product lines. Managing functional safety in industrial product lines is challenging and work around solutions are applied in practice. The objective of this research is to collect and review reported research publications focusing on achieving safety in product lines and to identify gaps in todays research. We conduct a systematic mapping study of research publications reported until January 2016.We identify 39 research articles to be included in a list of primary studies and analyze how product lines are documented, which safety-related topics are covered and which evaluation method the studies apply. Generally, we find that the area of how to achieve functional safety in product lines needs more attention. Our study provides an overview on which topics have been discussed until now and which safety-related topics need more attention.