Statistical Safety Performance Models considering Pavement and Roadway Characteristics

Table 3

Correlation coefficients between predictor variables (1,811 segments).

	2	3	4	5	6	7	8	9	10	11	12	13	14
(2) Ln_Lgth	1	−0.09	0.13	0.06	0.01	0.04	0.01	−0.11	−0.37	−0.03	0.14	0.09	0.18
(3) Ln_AADT	−0.12	1	−0.11	−0.27	0.08	0.07	0.06	0.28	0.41	0.48	0.10	−0.02	0.05
(4) Lq_MPD	0.13	−0.01	1	−0.23	−0.03	−0.13	−0.08	−0.63	−0.12	−0.13	0.03	−0.08	0.03
(5) Av_Frict	0.07	−0.27	−0.21	1	−0.10	−0.09	−0.14	0.20	−0.17	−0.02	−0.03	0.01	−0.07
(6) Av_Grad	−0.05	0.03	−0.02	−0.09	1	0.04	0.02	0.02	0.07	0.01	0.04	0.04	0.06
(7) Lg_Dgcv	−0.01	−0.02	−0.05	−0.03	0.01	1	0.62	0.09	0.21	−0.16	−0.06	0.16	0.15
(8) Ln_Lgcv	0.01	0.06	−0.09	−0.16	0.00	0.40	1	0.07	0.23	−0.19	−0.06	0.15	0.13
(9) PvType	−0.10	0.30	−0.52	0.15	0.03	0.04	0.07	1	0.14	0.25	−0.02	0.04	0.01
(10) RrloUrb	−0.38	0.42	−0.09	−0.19	0.06	0.12	0.23	0.13	1	0.09	−0.17	0.06	0.03
(11) ExsMdn	−0.04	0.56	−0.02	−0.02	0.00	−0.16	−0.20	0.24	0.09	1	0.16	−0.04	0.00
(12) ExsShd	0.15	0.08	0.06	−0.03	0.04	−0.06	−0.06	−0.02	−0.17	0.16	1	−0.09	−0.08
(13) RnkIRI	0.11	−0.01	−0.09	0.01	0.04	0.09	0.14	0.05	0.05	−0.04	−0.08	1	0.56
(14) RnkRut	0.19	0.06	0.05	−0.07	0.05	0.09	0.13	0.02	0.03	−0.00	−0.08	0.57	1

Note. 1. The abbreviation of variables is consistent with Table 2. 2. Lower triangular cells report Pearson’s correlation coefficient and upper triangular cells report Spearman’s rank correlation. 3. Significance indicated with -value: ＜0.01, ＜0.05, and ＜0.1.