1999年8月山东省东明县境内发生了一起大型拖拉机致死一人的重大交通事故。公安交通管理部门在勘查事故现场时发现拖拉机号牌和行驶证系公安车管部门核发，而肇事驾驶员的拖拉机驾驶证则为农机部门核发。在讨论这起事故责任如何认定时民警们对该驾驶证是否有效的问题发生了分歧 In August 1999, there was a major traffic accident in Dongming County, Shandong Province, with the death of a large tractor. Public security traffic management department at the scene of the accident investigation found that the tractor license plate and driving license issued by the Public Security Administration, while the driver of the tractor driver’s license issued by the Agricultural Machinery Department. In discussing how to determine the responsibility of the accident when the police were disqualified on the issue of the driver’s license