The blinding pollution arrived as the country's population prepared to travel to their hometowns for a New Year's celebration, the state-run Xinhua News Agency reported.
Sections of more than 20 freeways were closed in four central and eastern provinces, the Transport Ministry said. The roads were reopened by noon.
Visibility at Beijing Capital International Airport dropped to less than 650 feet, causing the cancellation of 49 flights on Tuesday. Most flights had resumed Wednesday as the fog lightened.
The fog did not affect the country's rail system. Another 526 trains were added to cope with travelers stymied for other means of transportation.