For many people, especially those who don’t live in and around Los Angeles, the idea of Sunset Boulevard conjures up the iconic Billy Wilder film of that name, or the fictional nightclub at 77 Sunset Strip, where one of the most popular TV series of the early 1960s was set, or images of historic Hollywood landmarks: the Chateau Marmont hotel, whose poolside bar is prime territory for movie-star sighting, and where several recent films (Sofia Coppola’s “Somewhere” and David Cronenberg’s “Maps to the Stars”) were shot; the Laugh Factory, where some of the country’s greatest comedians, from Richard Pryor and Jerry Seinfeld to Robin Williams and Eddie Murphy, have performed. But for Los Angeles residents, those two words — Sunset Boulevard — are more likely to seem like shorthand for their shared obsession: traffic.