China's transport system was tested on Wednesday as tourists returning from their May Day holiday trips pushed traffic flow in many places to record highs.

There were an estimated 2 million vehicles on the highways in Beijing on Wednesday, the last of the three-day holiday, a 41 percent rise from last year, according to the Beijing Municipal Commission of Transport.

A nationwide toll-free policy was implemented during the holiday, starting from Monday. It boosted tourism and increased the number of vehicles on the road.