Tesla is persisting with its plan to undercut the automotive insurance providers, signing another deal to expand its InsureMyTesla offering, this time with Liberty Mutual in the US. Now available in 20 countries, the company aims to ensure better rates for its customers, as a means of making its cars more price competitive, as well as paving the way for it to experiment with its self-driving technologies. The new deal comes as CEO Elon Musk continues to demand that insurers lower their premiums for Tesla cars, due to their better safety records and Autopilot technology – a contentious claim in both Silicon Valley and Detroit, but apparently backed by the NHTSA’s findings that crash rates for Teslas fell 40% since…