Analysis of Rear-End Crash on Thai Highway: Decision Tree Approach

Table 4

Correlation among independent variables.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22
(1) Vehicle types	1.00	−0.05	0.11	−0.20	0.07	0.02	−0.01	0.14	0.16	−0.03	−0.05	0.05	−0.03	0.02	0.07	0.08	0.06	−0.02	−0.02	0.09	0.15	0.03
(2) CrashType		1.00	0.01	0.02	−0.09	0.00	0.01	−0.10	−0.10	0.00	0.04	−0.07	0.16	0.16	−0.10	−0.08	−0.02	−0.05	0.00	−0.16	−0.10	−0.23
(3) Person_age			1.00	−0.13	−0.01	−0.02	−0.01	0.02	0.03	−0.01	0.02	0.00	0.01	0.02	0.00	0.01	−0.01	0.00	0.02	0.01	0.00	−0.04
(4) Gender				1.00	−0.02	−0.01	−0.01	−0.05	−0.04	0.00	0.02	−0.02	0.03	−0.03	−0.02	−0.02	−0.08	0.04	−0.01	−0.04	−0.04	0.00
(5) Main_Road					1.00	−0.02	−0.01	0.40	0.23	−0.17	0.06	−0.04	−0.05	−0.04	0.01	0.01	0.08	0.04	−0.01	0.35	0.07	0.06
(6) Entran_Exit						1.00	0.01	0.13	0.05	−0.01	0.02	−0.01	0.02	−0.03	−0.02	−0.02	0.00	0.00	−0.01	0.13	0.02	0.03
(7) Normal							1.00	0.06	0.05	−0.03	0.02	0.00	0.00	0.00	0.03	0.03	0.00	−0.02	0.02	0.05	0.01	−0.03
(8) Road_lane								1.00	0.62	−0.22	0.11	−0.09	−0.12	0.05	−0.01	−0.01	0.12	0.06	−0.05	0.60	0.17	0.09
(9) Road_isle									1.00	−0.13	0.12	−0.08	−0.12	0.16	0.02	0.03	0.09	0.09	−0.04	0.48	0.26	0.06
(10) Asphalt										1.00	−0.05	0.04	−0.06	−0.08	0.06	0.03	−0.10	0.07	0.03	−0.10	−0.04	−0.06
(11) Straight											1.00	−0.39	0.03	0.03	−0.11	−0.08	0.03	0.05	0.01	0.07	−0.07	0.01
(12) Slope												1.00	−0.05	−0.04	0.05	0.04	−0.02	−0.07	0.00	−0.06	0.09	−0.04
(13) Intersection													1.00	0.08	−0.07	−0.06	0.00	−0.06	0.03	−0.11	−0.05	−0.09
(14) Median_open														1.00	−0.02	−0.03	−0.01	−0.01	0.00	−0.05	0.03	−0.11
(15) Env_surfaces															1.00	0.84	−0.02	0.00	−0.01	−0.03	0.04	0.07
(16) Weather																1.00	0.02	0.00	0.01	−0.03	0.04	0.06
(17) Env_light																	1.00	−0.05	0.02	0.10	0.06	0.04
(18) SafetyEqui																		1.00	−0.01	0.08	−0.01	0.00
(19) Alcohol																			1.00	−0.04	−0.04	−0.08
(20) AADT60																				1.00	0.03	0.12
(21) PerCTruck																					1.00	0.03
(22) SpeedExc																						1.00

Note: Bold number represented correlation, which is significant at the 0.05 level (2-tailed).