The risk of Tesla’s Model S sedan catching fire has been reduced to “virtually zero,” wrote Tesla CEO Elon Musk in a blog post Friday. Thanks to a titanium shield sandwiched between a rounded, hollow aluminum bar and a shallow angle, solid aluminum extrusion, Model S sedans built after March 6 are supposedly safer than ever, a fine feat considering the National Highway Traffic Safety Administration named it the safest car it ever tested. Tesla focused on strengthening the cars underside after it found two Model S fires — one in Seattle, Wash. and the other in Smyrna, Tenn. —