An Investigation of the Safety Performance of Roundabouts in Korea Based on a Random Parameters Count Model

Table 6

Average marginal effects and elasticities for random parameter negative binomial models.

Variable	Marginal effect	Elasticity
Logarithm of AADT	0.34	0.23
Width of entry/exit lanes	0.24	0.70
Central island (yes: 1; otherwise: 0)	1.49	0.63
Width of the circle lanes in the roundabout (m)	-0.44	-1.54
Radius of the entry lanes (m)	-0.06	-0.87
Number of approach/exit lanes	0.21	0.16
Pedestrian crosswalk (yes: 1; otherwise: 0)	0.97	0.48
Vertical grade (yes: 1; otherwise: 0)	-0.93	-0.88