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

Table 2

Triggering conditions related to-traffic situations.

Layer 1	Layer 2	Layer 3	Layer 4	Layer 5
Alignment	Point of occurrence	Traffic obstacle factors	Accident type	Day and night
Inclination		Road environment	Traffic obstacle factors	Weather
Cut and fill		Main accident cause	Vehicle operation just before the accident
		Accident cause	Main accident type