General Motors CEO Mary Barra arrives to testify before the House Energy and Commerce Committee hearing on Capitol Hill in Washington April 1, 2014. U.S. lawmakers, seeking to establish who is to blame for at least 13 auto-related deaths over the past decade, challenged Barra on Tuesday afternoon over the automaker's slow response to defective ignition switches in its cars. REUTERS/Jonathan Ernst (UNITED STATES - Tags: POLITICS TRANSPORT BUSINESS)