Table 1: ZINB models for segment crash frequency analyses and predictions.

RoleVariablesTypesDescription

Dependent variableNum_crshContinuousNumber of crashes (crash frequencies)

ADT_1000ContinuousAverage thousand daily traffic (thousand vehicles per day)
LengthContinuousThe length of a segment (mile)
FFSContinuousFree flow speed in road segment (mph)
Independent variableDaily_VMTContinuousAverage daily Vehicle Mile Traveled (VMT)
RorUDiscreteRural or urban: 0 = urban; 1 = rural
FCDiscreteSegment functional classification: 0 = interstate; 1 = expressway; 2 = arterial; 3 = M_Arterial
NumberoflaDiscreteNumber of lanes: 0 = 2 lanes; 1 = 4 lanes