Spatial Influence Analysis of Traffic Safety in Diverging Areas between Freeway Segments and Off Ramps

Table 4

p value of variables for different buffer size.

Variables	30 feet		60 feet		90 feet		120 feet		150 feet		180 feet		210 feet		240 feet		270 feet		300 feet
	Coef.	-V	Coef.	-V	Coef.	-V	Coef.	-V	Coef.	-V	Coef.	-V	Coef.	-V	Coef.	-V	Coef.	-V	Coef.	-V
(Intercept)	−3.887	0.486	−1.711	0.493	−4.794	0.044	−3.210	0.134	−4.157	0.024	−5.174	0.003	−3.103	0.077	−2.488	0.102	−1.837	0.221	−.817	0.583
Ramp.Lanes = 0	1.742	0.068	.396	0.517	.700	0.257	.733	0.189	.843	0.067	.981	0.025	.835	0.043	.893	0.016	.855	0.021	.419	0.251
Up_Interstate.Lanes = 0	−.643	0.512	−1.525	0.008	−.881	0.134	−.690	0.176	−.484	0.270	−.538	0.211	−.312	0.459	−.279	0.471	−.406	0.302	−.626	0.107
Down_Interstate.Lanes = 0	−.168	0.876	.713	0.309	.881	0.210	.995	0.106	1.363	0.012	1.646	0.001	.955	0.055	.887	0.051	.897	0.051	1.089	0.020
PSR = 0	1.435	0.196	.631	0.286	.542	0.408	.110	0.845	.245	0.595	.202	0.643	−.200	0.669	−.226	0.564	−.260	0.502	−.372	0.333
Median_Type = 0	−.699	0.618	−.605	0.428	−.597	0.411	−.529	0.419	−.894	0.112	−.562	0.304	.467	0.371	.320	0.502	.494	0.319	.613	0.203
Truck_Percent = 0	−1.602	0.365	−.355	0.699	1.393	0.093	1.336	0.076	1.377	0.043	1.558	0.019	1.084	0.101	1.208	0.045	1.352	0.026	1.134	0.064
Ramp.Length	−5.508	0.315	−5.080	0.086	−4.375	0.154	−3.381	0.188	−2.260	0.294	.160	0.932	.249	0.894	−.251	0.880	−.142	0.932	−.499	0.751
Ramp_ADT	−.019	0.860	−.137	0.207	−.068	0.325	−.040	0.471	.008	0.843	.017	0.677	−.009	0.828	.002	0.951	−.019	0.588	−.036	0.306
Up_Interstate.Length	.883	0.062	.798	0.060	.406	0.358	.397	0.306	.130	0.671	.185	0.544	.200	0.537	.204	0.475	.295	0.307	.043	0.871
Up_Interstate_ADT	.019	0.858	.137	0.206	.068	0.324	.040	0.469	−.008	0.846	−.017	0.680	.009	0.824	−.002	0.956	.020	0.584	.036	0.304
Down_Interstate.Length	−4.215	0.225	−.283	0.897	−.153	0.945	−.405	0.824	−.176	0.909	−.687	0.639	−1.328	0.372	−1.539	0.249	−1.728	0.202	−1.067	0.398
Down_Interstate_ADT	−.019	0.857	−.137	0.206	−.068	0.324	−.040	0.470	.008	0.845	.017	0.679	−.009	0.825	.002	0.954	−.019	0.585	−.036	0.305
IRI	.178	0.861	.324	0.588	.270	0.709	.015	0.982	.140	0.792	.373	0.455	−.145	0.793	−.280	0.522	−.347	0.420	−.528	0.226
Median_Width	.152	0.169	.001	0.983	.034	0.515	.024	0.625	.037	0.401	.020	0.646	−.058	0.165	−.037	0.334	−.041	0.305	−.066	0.085
SPEED_LIMI	.009	0.784	.010	0.510	.021	0.090	.012	0.245	.013	0.188	.013	0.139	.017	0.046	.013	0.078	.010	0.191	.013	0.094
	.617	—	1.110	—	1.363	—	1.112	—	.830	—	.783	—	.766	—	.625	—	.659	—	.649	—