BEIJING, May 1 (Xinhua) -- China has acted to ensure travelers a safe trip during the May Day holiday starting Wednesday.

The Ministry of Public Security has warned the public of the risks including peak flows on expressways and around tourist sites, heavy rainfall, and more traffic violations.

Police have been drafted to secure major transportation hubs such as key railway stations and trains.

Tighter security checks are required and patrol has become more frequent, railway police authorities say.

Ctrip, China's largest online travel agency, estimated that about 160 million trips will be made during this year's four-day May Day holiday.