BEIJING >> Transportation officials in China say Lunar New Year holiday travel has been generally smooth ahead of the biggest travel days of the year.

About 230 million people — more than the entire population of Brazil — are expected to take part in the world’s biggest annual human migration. For many, it’s the only chance they get to visit home all year.

The busiest travel days will be Monday and Tuesday, as millions take to the roads, boats, planes and trains to join family for the traditional New Year’s Eve “reunion meal.” The Lunar New Year falls on Thursday.

Icy roadways have caused the most problems so far for those traveling by car and bus, with traffic backed up in some parts of southern China, Vice Minister of Transport Feng Zhenglin said at a news conference Sunday.

“Several major roads in Guizhou, Chongqing and Hunan have quite thick ice, and workers are busy clearing that right now,” he said, without giving a figure for the number of affected travelers.

Slippery road conditions were also to blame when a bus plunged into a ravine in northwestern China’s Ningxia region, killing 11 and injuring 22, the official Xinhua News Agency said.

Deputy railways minister Wang Zhiguo said 58.3 million people have taken trains in the first 11 days of the holiday travel season that runs through Feb. 27. Authorities have put thousands of extra carriages into service, opened additional ticket offices and cracked down on scalpers, he said.

Still, travelers have complained that train tickets are hard to come by as in previous years.

Authorities have improved emergency planning and coordination since a freak winter storm in 2008 crippled the transportation system during the holiday season and stranded hundreds of thousands of people.