An Assessment of the Safety Effects of Roadside Barriers on Reducing Mountainous Crash Injury Severity

Table 3

Model results for W-beam barriers crashes in 2016-2017.

Variables	Coefficient	t-stat	Pseudoelasticities (%)
			Severe injury (SI)	Minor injury (MI)	No injury (NI)
Constant (SI)	−1.618	−5.22	—	—	—
Constant (MI)	−1.466	−3.61	—	—	—
Random parameter (normally distributed)
Dark-lighted indicator (1 if yes; otherwise, 0) (MI)	0.693	2.09	−9.77	35.78	−9.77
Standard deviation of the parameter density function	1.506	2.06	—	—	—
Heterogeneity in the mean of random parameter
Dark-lighted indicator (1 if yes; otherwise, 0) (MI): improper braking and steering indicator (1 if yes; otherwise, 0)	0.998	1.74	—	—	—
Vehicle characteristics
Truck indicator (1 if yes; otherwise, 0) (SI)	0.713	3.46	12.06	−6.25	−6.40
Truck indicator (1 if yes; otherwise, 0) (MI)	−1.607	−3.06	1.02	−39.21	1.02
Improper braking and steering indicator (1 if yes; otherwise, 0) (SI)	2.671	6.45	90.31	−26.38	−27.64
Improper braking and steering indicator (1 if yes; otherwise, 0) (NI)	2.518	6.37	−76.08	−69.30	35.09
Improper lane changing indicator (1 if yes; otherwise, 0) (MI)	−1.773	−3.76	2.12	−14.69	2.12
Speeding indicator (1 if yes; otherwise, 0) (NI)	−2.634	−6.49	3.95	3.95	−70.93
Nonlocal vehicle indicator (1 if yes; otherwise, 0) (SI)	0.544	2.05	4.86	−2.39	−2.49
Roadway characteristics
Road in bad condition indicator (1 if yes; otherwise, 0) (SI)	−1.725	−2.22	−4.94	0.39	0.41
Road in bad condition indicator (1 if yes; otherwise, 0) (MI)	−2.040	−2.17	0.44	−5.23	0.44
Homogeneous section indicator (1 if yes; otherwise, 0) (SI)	−1.576	−8.28	−87.88	17.95	18.96
Homogeneous section indicator (1 if yes; otherwise, 0) (MI)	−1.010	−3.44	8.44	−53.60	8.44
Intersection indicator (1 if yes; otherwise, 0) (NI)	1.033	3.50	−11.37	−10.45	4.64
Ramp indicator (1 if yes; otherwise, 0) (NI)	2.079	3.93	−7.08	−6.65	1.36
Large downhill grade indicator (1 if −2% or less vertical grade; otherwise, 0) (SI)	−1.764	−3.99	−15.37	1.88	1.90
Crash characteristics
Sideswipe indicator (1 if yes; otherwise, 0) (MI)	1.110	3.84	−8.31	36.09	−8.31
Head-on collision indicator (1 if yes; otherwise, 0) (NI)	−0.962	−3.32	4.84	4.62	−3.77
Sunny indicator (1 if yes; otherwise, 0) (SI)	−1.161	−4.67	−28.81	3.42	3.48
Medium-low visibility indicator (1 if 50–100 meters; otherwise, 0) (SI)	0.691	3.33	16.31	−5.46	−5.88
Low visibility indicator (1 if below 50 meters; otherwise, 0) (NI)	−0.738	−2.69	4.57	4.07	−3.36
Dark lighted indicator (1 if yes; otherwise, 0) (SI)	−1.064	−4.47	−33.18	2.98	4.26
Number of observations above and below zero generated from the random parameter	Above zero		Below zero
Dark-lighted indicator (1 if yes; otherwise, 0) (MI)	97.14%		2.86%
Goodness-of-fit measures
McFadden R-squared	0.374

, , ==> significance at 0.99, 0.95, and 0.90 level of confidence, respectively.