Development of Risk-Situation Scenario for Autonomous Vehicles on Expressway Using Topic Modeling

Table 13

Top three topic distribution by group.

Cause	Group	Layer 1		Layer 2		Layer 3		Layer 4		Layer 5
		Alignment	Inclination	Point of occurrence	Traffic obstacle factors	Road environment	Main accident cause	Vehicle operation	Main accident type	Day and night	Weather
Vehicle	1			o	o					o
	2			o			o		o
	3	o		o			o
	4		o	o			o
Other	1			o	o					o
	2			o			o				o
	3	o		o	o	o			o
	4			o	o			o			o