Determining Causal Factors of Severe Crashes on the Fort Peck Indian Reservation, Montana

Table 3

Logistic regression: parameter estimates and odds ratios for all roadways.

Variables	Estimate	Std. Error	p value	Odds ratio	Confidence interval
					2.50	97.50
All roads
(Intercept)	2.118	0.183	< 0.001
Impaired driving	1.829	0.185	< 0.002	6.23	4.35	9.00
Adverse Weather	0.346	0.169	0.041	1.41	1.01	1.97
Overturn	1.627	0.247	< 0.001	5.09	3.17	8.34
Ditch	1.138	0.324	< 0.001	3.12	1.67	5.99
Pedestrians	2.951	0.658	< 0.001	19.12	5.97	85.82
IRR	1.473	0.287	< 0.001	4.36	2.50	7.69
State Highway	0.932	0.197	< 0.001	2.54	1.74	3.76
Indian Reservation Roads
(Intercept)	-0.637	0.344	0.06
Impaired driving	2.630	0.587	< 0.001	13.88	4.86	50.94
Overturn	1.572	0.504	< 0.001	4.82	1.85	13.53
Ditch	1.245	0.633	< 0.001	3.47	1.05	13.00
Roads maintained by city and county highway agency
(Intercept)	-2.177	0.233	< 0.001
Impaired driving	1.618	0.402	< 0.001	5.04	2.28	11.14
Fixed Objects	0.935	0.411	0.023	2.55	1.12	5.65
Curve	2.104	0.723	< 0.01	8.20	1.96	36.18
Roads maintained by state highway agency
(Intercept)	-0.902	0.122	< 0.0001
Impaired driving	1.572	0.232	< 0.0001	4.82	3.08	7.66
Overturn	1.417	0.289	< 0.0001	4.12	2.37	7.39
Ditch	1.082	0.398	< 0.0001	2.95	1.38	6.65