Table 4.

Predictors of bicycle-motor vehicle crashes occurring at non-intersections compared to intersections, Iowa, 2001-2011.

	Multivariable Logistic Regression
	Model 1 Person		Model 2 Person & Crash		Model 3 Person, Crash, & Environment		Model 4 Person, Crash, Environment, & Population		Model 5- Final Model
Variable	N=4437		N=4437		N=4405		N=4291		N=4405
Person Characteristics	OR	95% CI	OR	95% CI	OR	95% CI	OR	95% CI	OR	95% CI
Age, bicyclist
<10	1.9	1.4-2.6	1.9	1.3-2.8	1.8	1.2-2.5	1.8	1.2-2.6	1.8	1.2-2.6
10-14	1.1	0.8-1.5	1.2	0.8-1.7	1.1	0.8-1.6	1.2	0.8-1.6	1.1	0.8-1.6
15-19	0.8	0.6-1.2	1.0	0.7-1.5	1.0	0.7-1.5	1.0	0.7-1.5	1.0	0.7-1.5
20-29	1.0	0.7-1.3	1.3	0.9-1.8	1.2	0.8-1.7	1.3	0.9-1.9	1.2	0.8-1.8
30-59	1.0	0.8-1.4	1.1	0.8-1.6	1.1	0.8-1.5	1.1	0.8-1.6	1.1	0.8-1.5
60+	1.0	Ref	1.0	Ref	1.0	Ref	1.0	Ref	1.0	Ref
Unknown	0.8	0.5-1.2	0.8	0.5-1.3	0.8	0.5-1.2	0.8	0.5-1.2	0.8	0.5-1.2
Gender, bicyclist
Female	1.0	Ref	1.0	Ref
Male	1.2	1.0-1.3	1.1	1.0-1.3
Unknown	1.2	0.7-2.2	1.2	0.6-2.1
Gender, motorist
Female	1.0	Ref	1.0	Ref
Male	1.2	1.1-1.4	1.1	1.0-1.3
Unknown/Not-reported	1.4	1.1-1.7	1.1	0.9-1.4
Crash Characteristics
Location
Rural (outside city limits)			5.9	4.1-8.6	5.0	3.3-7.5	5.9	4.0-8.7	5.7	3.9-8.3
Urban (within city limits)			1.0	Ref	1.0	Ref	1.0	Ref	1.0	Ref
Unknown			1.9	1.2-3.2	2.0	1.2-3.3	n/a		n/a
Contributing circumstances, bicyclist
Improper crossing (Ref=no)			0.5	0.3-0.8	0.7	0.5-1.0	0.7	0.6-1.0	0.7	0.5-0.9
Darting (Ref=no)			0.7	0.4-1.1
Failure to yield right of way (Ref=no)			0.3	0.2-0.5	0.4	0.3-0.6	0.4	0.3-0.6	0.4	0.3-0.6
Failure to obey traffic signs/signals/officer (Ref=no)			0.1	0.1-0.2	0.1	0.1-0.2	0.1	0.1-1.2	0.1	0.1-0.2
Contributing circumstances, motorist
Failure to yield right of way (Ref=no)			0.4	0.3-0.6	0.6	0.4-0.8	0.6	0.4-0.8	0.6	0.4-0.8
Swerving/evasive action (Ref=no)			0.6	0.4-1.0
Major Cause (from police report)
Both bicyclist and motorist			3.0	1.7-5.4	1.5	1.0-2.2	1.6	1.1-2.3	1.5	1.0-2.2
Motor vehicle only			1.8	1.2-2.7	1.2	0.9-1.7	1.2	0.9-1.7	1.2	0.9-1.7
Bicyclist only			2.1	1.4-3.2	1.6	1.3-2.1	1.6	1.3-2.1	1.6	1.3-2.1
Neither			1.0	ref	1.0	ref	1.0	ref	1.0	ref
Motor vehicle action
Moving essentially straight			1.0	ref	1.0	ref	1.0	ref	1.0	ref
Turning (L, R, or U-turn)			0.4	0.3-0.4	0.4	0.3-0.4	0.4	0.3-0.4	0.4	0.3-0.4
Other/Unknown			1.3	1.1-1.7	1.4	1.1-1.7	1.4	1.1-1.7	1.4	1.1-1.7
Environmental Characteristics
Posted Speed Limit (mph)
25 & Under					1.0	ref
30-35					0.9	0.8-1.1
40-50					1.0	0.7-1.5
55+					1.2	0.9-1.6
Vision obscurement
No					1.0	ref	1.0	ref	1.0	ref
Yes					1.5	1.2-1.8	1.5	1.2-1.9	1.5	1.2-1.8
Unknown					1.1	0.9-1.4	1.2	1.0-1.4	1.2	1.0-1.4
Reduced Lighting
No (daylight or lighted roadway)					1.0	ref	1.0	ref	1.0	ref
Yes (dusk, dawn, unlighted roadway)					1.9	1.5-2.4	1.9	1.5-2.5	1.9	1.5-2.4
Unknown					1.2	0.5-2.8	1.1	0.5-2.6	1.2	0.5-2.8
Population Characteristics (based on 2010 census)
Population density by zip code (state quartiles)
0-466							0.7	0.3-1.6
467-1013							1.5	0.9-2.5
1014-2456							0.9	0.7-1.1
2457+							1.0	ref
Median Household Income ($USD)
Above state median							1.0	0.9-1.2
Below state median							1.0	Ref
% High School Degree or Higher
Above state median							0.9	0.8-1.1
Below state median							1.0	Ref
% Bachelor's Degree or Higher
Above state median							0.9	0.8-1.1
Below state median							1.0	ref

Notes: All models are adjusted, with all variables in the column included. Ref=referent; mph = miles per hour; $USD = United States dollars.

The sample size, N, decreases in Models 3,4, and 5 due to missing values.

Adjusted R²: Model 1 (0.03), Model 2 (0.20), Model 3 (0.21), Model 4 (0.21), Model 5 (0.21).

Likelihood ratio tests: Model 2 vs. Model 1 (χ2=641.15, df=13, p<0.001), Model 3 vs. Model 2 (χ2=73.75, df=1, p<0.001), Model 4 vs.

Model 3 (χ2=137.02, df=2, p<0.001), Model 4 vs. Model 5 (χ2=140.42, df=5, p<0.001).

Variables included in successive models (2-5) had to meet criteria of p<0.05