In October 1997 the Swedish Parliament adopted a new road safety policy – Vision Zero. Vision Zero entails a fundamentally new division of responsibility for traffic safety between road users and the so called system designers such as road administrations, municipalities, and professional transport companies among others. In this study the implementation of a formal responsibility for system designers to prevent serious injuries in road traffic between 1997 and 2009 is evaluated. Two main research questions have guided this study namely: How has the legislative process of formalizing the responsibility of system designers progressed? and What important factors might explain the implementation outcome? The main sources of information for this study were official key documents. Based on a goal attainment model, an important conclusion is that the goal to legally formalize a responsibility has only been minimally realized and therefore this might be an example of a classic implementation failure. In order to explain and discuss this low level of achievement a process evaluation approach has also been used. Built on this process evaluation approach, it can be questioned if this is an example of implementation failure after all.