Overturning tractors are a major cause of death for farmers around the world. In 2016, 417 farmers and farm workers died from a work-related injury in the United States and 312 in Japan, according to the Center for Disease Control.

Now, scientists from the Tokyo University of Agriculture and Technology have made a discovery that could contribute to reducing the number of accidents caused by overturning tractors. The researchers sought to understand what makes a tractor overturn.

“As most farm tractors don’t have suspension systems, violent vibrations can occur in the tractor and the wheels sometimes depart from the ground in what is called a ‘bouncing’ phenomenon,” said Kenshi Sakai, professor of environmental and agricultural engineering in the Institute of Agricultural Science at Tokyo University of Agriculture and Technology. “Standard models of farm tractors have not accounted for this bouncing process.”

Through the use of computer simulations, scientists examined how a tractor would react to a number of bouncing scenarios. They observed that bouncing is especially serious when tractors run on steep slopes, especially if it’s more than 18 degrees.

“To describe such serious, violent and unexpected dynamics behavior occurring in farm tractors and vehicles, it is essential to implement the bouncing process in the model,” Sakai said. “Our proposed model could be a new paradigm in farm tractor modeling.”