Hebei people can earn 60,000-90,000 yuan a year pulling coal. The average monthly salary of Hebei people pulling coal semi-trailers is 5000 -8000 yuan, and it is 8000 yuan a month to pull coal to a place for a long time. Multiply the monthly salary by 12, and you can get the money you earn in one year, 60,000-90,000 yuan. Semi-trailer is a trailer whose axle is placed behind the center of gravity of the vehicle and equipped with a coupling device that can transmit horizontal and vertical forces to the tractor. Semi-trailer is a three-axle semi-trailer, which is divided into eleven-meter barn semi-trailer, thirteen-meter barn semi-trailer, low-level semi-trailer and other types. It is a heavy transport vehicle connected with the front of a semi-trailer through a traction pin.