LOS ANGELES — One year ago, a 10-mile stretch of Interstate 405 — the most heavily traveled highway in the nation, and the not-so-proud symbol of the Los Angeles traffic jam — was shut down for most of a weekend. The city went on full alert. Emergency workers were mobilized, contingency plans were made and motorists were warned — in the most dire terms — to stay off the road for what was called Carmageddon.

In a week, it will happen again in what is the next phase in widening the highway as it cuts through the narrow Sepulveda mountain pass that connects west Los Angeles and the San Fernando Valley. Yet this time, you would hardly know it.

There are no apocalyptic warnings from the mayor, no reports of people preparing to flee town. The flashing warning signs posted on roadways across California appear both less prevalent and less terrifying.

Lady Gaga has yet to post another stay-off-the-road Twitter message to her 29.4 million followers. And a click on the Facebook page that last year was devoted to Carmageddon recently returned this message: “The page you requested was not found.”