(Reuters) – Sidecar, a ride-sharing startup which competes with on-demand car services such as Uber and Lyft, said it raised $15 million from existing and new investors, including Virgin Group founder Richard Branson. Existing investors Avalon Ventures and Union Square Ventures also participated in the funding round, the company wrote in a blog post. Sidecar, which uses a smartphone-based app to match riders with drivers, plans to expand in the United States to match the reach of its rivals. (Reporting By Sai Sachin R; Editing by Joyjeet Das)