Beijing issued its first-ever red alert for smog on Monday, urging schools to close and invoking restrictions on factories and traffic that will keep half of the city's vehicles off the roads. The red alert—the most serious warning on a four-tier system adopted a little over two years ago—means authorities have forecast more than three consecutive days of severe smog. An online notice from the Beijing Municipal Environmental Protection Bureau said it issued the alert to "protect public health and reduce levels of heavy air pollution."
Along with school closures and limiting cars to driving every other day depending on the last number of their license plate, a raft of other restrictions will seek to reduce the amount of dust and other particulate matter in the city of 22.5 million people. Officials said extra subway trains and buses would be added to handle the additional strain on public transport. There previously have been stretches of severe smog in Beijing that lasted more than three days. However, those had initially been forecast to last three days or less, so they did not trigger a red alert. (Read more Beijing stories.)