Table 1.

Independent variables of severity of hazardous materials transportation accident.

Variable Category	Variable Name	Variable Description
Driver properties	Violation	1: illegal carriage, 2: overload, 3: fatigue driving
	Unsafe driving behavior	1: Failure to maintain a safe distance; 2. Improper operation; 3. Excessive speed
	Accident liability	1:hazardous materials vehicles, 2:other vehicles
Vehicle properties	Packaging problem	1: valve failure; 2: broken tank; 3: tank fire
	Vehicle problem	1:flat tire, 2:vehicle control, 3: brake failure, 4:engine fire, 5:other causes, 6: other vehicle causes
	Model category	1: tank truck, 2:oil tank truck, 3: illegally modified vehicle, 4: truck
Environmental properties	weather	1: sunny, 2: cloudy, 3: rainy, 4: haze
	Lighting (time)	1: daytime, 2: night lighting, 3: night without lighting
	Month distribution	1: first quarter, 2: second quarter, 3: third quarter, 4: fourth quarter
Road properties	Road grade	1: expressway, 2: national highway, 3: provincial highway, 4: county road and below, 5: urban road(intersection)
	Regional distribution	1: North China, 2: East China, 3: South China, 4: Central China, 5: Northwest China, 6: Southwest China, 7: Northeast China