Exploring Relationships between Months and Different Crash Types on Mountainous Freeways Using a Combined Modeling Approach

Table 1

Results of K-means clustering.

Total crash number				Rear-end
Cluster	Month	Avg. crash number	Risk level	Cluster	Month	Avg. crash number	Risk level
1	1	46.5	3	1	1, 8, 9, 10, 11	12.0	3
2	5, 6, 7, 8	44.8	3	2	3, 4, 5, 6, 12	9.2	2
3	10, 11	40.3	2	3	2, 7	8.1	1
4	3, 4, 9	38.9	1
5	2, 12	38.4	1
Fixed-object hitting				Overturning
Cluster	Month	AVG crash number	Risk level	Cluster	Month	AVG crash number	Risk level
1	6, 7, 8	28.5	3	1	10	7.3	3
2	1, 2	26.1	3	2	5, 6, 7, 8, 11	4.8	2
3	3, 4, 9	21.6	2	3	2	4.5	2
4	12	21.3	2	4	3, 9, 12	3.7	1
5	5, 10, 11	20.2	1	5	1, 4	3.0	1