Joint standardisation of Cooperative Systems (V2V and V2I) is a core objective of the EU-US cooperation on Intelligent Transport Systems (ITS). In 2012, two Harmonisation Task Groups worked in parallel on analyses of security standards (HTG1) and Communications Standards (HTG3). The HTG1 analysis indicated that the initial set of security standards, developed by IEEE, was reasonably well harmonized. However, gaps still exist and must be addressed before large-scale deployment occurs. The HTG3 analysis involves the current differences between the EU and U.S. approach to standardizing communications at 5.9GHz for V2V and V2I safety-of-life and property communications. The HTG3 identified differences that presented interoperability challenges and offered suggestions for harmonizing these differences to achieve a single global standard. Both Harmonisation Task Groups' reports plus an introductory report and a report documenting the lessons learned in conducting the harmonisation activity, altogether ten papers, can be found here below.