Tesla Motors Inc on Thursday took its first step toward automated driving, unveiling features that will allow its electric sedan to park itself and sense dangerous situations. The car is like having a “personal roller coaster,” Tesla CEO Elon Musk joked after making the announcement at the packed event in Hawthorne, California. Tesla’s announcement had been eagerly anticipated since Musk last week tweeted that it was “about time to unveil the D and something else.” He cautioned, however, that “autopilot” was not fully autonomous driving and would not allow a driver to fall asleep at the wheel.