People view train models at a train exhibition in Dallas, Texas, the United States, Dec. 19, 2019. "The Trains at NorthPark" exhibition in Dallas has become one of the premier holiday traditions. (Xinhua/Dan Tian)

People view train models at a train exhibition in Dallas, Texas, the United States, Dec. 19, 2019. "The Trains at NorthPark" exhibition in Dallas has become one of the premier holiday traditions. (Xinhua/Dan Tian)

People view train models at a train exhibition in Dallas, Texas, the United States, Dec. 19, 2019. "The Trains at NorthPark" exhibition in Dallas has become one of the premier holiday traditions. (Xinhua/Dan Tian)

People view train models at a train exhibition in Dallas, Texas, the United States, Dec. 19, 2019. "The Trains at NorthPark" exhibition in Dallas has become one of the premier holiday traditions. (Xinhua/Dan Tian)

Children view train models at a train exhibition in Dallas, Texas, the United States, Dec. 19, 2019. "The Trains at NorthPark" exhibition in Dallas has become one of the premier holiday traditions. (Xinhua/Dan Tian)

Train station models are displayed at a train exhibition in Dallas, Texas, the United States. "The Trains at NorthPark" exhibition in Dallas has become one of the premier holiday traditions. (Xinhua/Dan Tian)