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

Table 5

Model results for flexible barriers crashes in 2016-2017.

Variables	Coefficient	t-stat	Pseudoelasticities (%)
			Severe injury (SI)	Minor injury (MI)	No injury (NI)
Constant (NI)	1.198	1.98	—	—	—
Constant (MI)	1.194	2.10	—	—	—
Random parameter (normally distributed)
Road without isolation indicator (1 yes; otherwise, 0) (NI)	1.689	2.98	−4.22	−4.22	12.14
Standard deviation of the parameter density function	1.490	2.85	—	—	—
Heterogeneity in the mean of random parameter
Road without isolation indicator (1 if yes; otherwise, 0) (NI): homogeneous section indicator (1 if yes; otherwise, 0)	−0.916	−2.01	—	—	—
Heterogeneity in the variance of random parameter
Road without isolation indicator (1 if yes; otherwise, 0) (NI): high visibility indicator (1 if above 200 meters; otherwise, 0)	1.149	2.35	—	—	—
Driver characteristics
No seatbelt use indicator (1 if yes; otherwise, 0) (SI)	1.624	3.01	11.84	−5.77	−3.28
Driver under alcohol influence indicator (1 if yes; otherwise, 0) (NI)	−2.280	−6.26	6.12	6.12	−25.95
Vehicle characteristics
Truck indicator (1 if yes; otherwise, 0) (MI)	−2.443	−4.33	4.08	−30.67	2.36
Truck indicator (1 if yes; otherwise, 0) (NI)	−0.847	−1.81	5.90	5.90	−2.97
Speeding indicator (1 if yes; otherwise, 0) (SI)	1.903	3.47	35.25	−10.85	−4.03
Speeding indicator (1 if yes; otherwise, 0) (NI)	1.489	3.66	−21.89	−21.89	5.52
Roadway characteristics
Homogeneous section indicator (1 if yes; otherwise, 0) (SI)	−1.600	−3.57	−103.25	16.86	7.40
Small uphill grade indicator (1 if 0–2% vertical grade; otherwise, 0) (SI)	−1.026	−2.74	−66.45	10.25	4.41
Crash characteristics
Sideswipe indicator (1 if yes; otherwise, 0) (SI)	−1.316	−3.53	−71.14	8.40	3.54
Summer indicator (1 if yes; otherwise, 0) (SI)	−1.117	−2.16	−27.74	2.47	0.95
Medium visibility indicator (1 if 100–200 meters; otherwise, 0) (SI)	−1.005	−1.96	−30.22	2.06	1.12
High visibility indicator (1 if above 200 meters; otherwise, 0) (MI)	−1.526	−2.73	6.82	−19.83	2.18
Daylight indicator (1 if yes; otherwise, 0) (SI)	2.310	4.60	83.99	−24.02	−8.83
Daylight indicator (1 if yes; otherwise, 0) (NI)	1.988	6.24	−55.75	−55.75	14.62
Temporal characteristics
Morning peak indicator (1 if time 7:00–8:59; otherwise, 0) (SI)	1.368	2.59	23.06	−5.06	−3.46
Morning peak indicator (1 if time 7:00–8:59; otherwise, 0) (MI)	0.950	2.94	−10.09	9.44	−7.64
Afternoon peak indicator (1 if time 17:00–19:29; otherwise, 0) (NI)	0.709	2.98	−12.04	−12.04	7.39
Number of observations above and below zero generated from the random parameter	Above zero		Below zero
Road without isolation indicator (1 if yes; otherwise, 0) (NI)	89.15%		10.85%
Goodness-of-fit measures
McFadden R-squared	0.435

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