Influence of Multiple Freeway Design Features on Freight Traffic Safety

Table 3

MARS model for total crashes.

Basis function	Basis function information	Coefficient	Standard error	-value
—	Constant	3.7795	0.0823	<0.0001
Basis1	MAX(Ln(AADT)—11.440354772,0)	—	—	—
Basis2	MAX(11.440354772—Ln(AADT),0)	−1.1183	0.1148	<0.0001
Basis3	Inside rumble strips	−0.1828	0.1001	0.0679
Basis4	Basis1 ∗ MAX(Inside shoulder width—13,0)	0.6995	0.1628	<0.0001
Basis5	Basis1 ∗ MAX(13—Inside shoulder width,0)	0.1054	0.0350	0.0026
Basis7	Basis1 ∗ MAX(14—Inside shoulder width,0)	0.1052	0.0378	0.0054
Basis8	Curve	—	—	—
Basis10	Basis8 ∗ MAX(Inside shoulder width—9,0)	−0.1264	0.0291	<0.0001
Basis12	Basis3 ∗ MAX(Ln(AADT)—12.022636468,0)	−4.5393	1.5719	0.0039
Basis13	Basis3 ∗ MAX(12.022636468—Ln(AADT),0)	0.2148	0.0963	0.0257
Basis14	Basis8 ∗ MAX(Ln(AADT)—10.599605317,0)	0.2415	0.0669	0.0003
Basis15	Basis8 ∗ MAX(10.599605317—Ln(AADT),0)	−0.3449	0.1616	0.0329
Basis16	Basis3 ∗ MAX(Inside shoulder width—13,0)	0.1178	0.0709	0.0963
Basis18	MAX(Inside shoulder width—13,0)	−0.1160	0.0495	0.0191
Basis19	MAX(13—Inside shoulder width,0)	−0.0365	0.0095	0.0001
Basis20	Outside rumble strips	−0.1062	0.0459	0.0437
AIC = 15920.28