A New GNB Model of Crash Frequency for Freeway Sharp Horizontal Curve Based on Interactive Influence of Explanatory Variables

Table 3

Models and statistics parameters.

Model	The basic function form of model	Estimated parameters
1; (NB)
2; (NB)	2.1	,
	2.2
	2.3
3; (GNB)
	4; (GNB)
4.1
4.2
4.3
5; (NB+translog +flexibility)		,
6; (GNB +translog +flexibility)

: overdispersion parameter. The higher is, the more scattered the distribution is. represent T, L, R, TR, TL, RL, and TRL of segment . The determining method is discussed in Section 4.