What are `primary_ramp` and `secondary_ramp`?

[agude]

The columns primary_ramp and secondary_ramp don't match everything I would expect from the codebook: https://tims.berkeley.edu/help/SWITRS.php

SELECT primary_ramp, secondary_ramp, count(1) as total
FROM collisions
GROUP BY 1,2
ORDER BY 3 DESC
LIMIT 500;

Yields:

	primary_ramp	secondary_ramp	total
0			5352014
1	TO		60595
2	FR		25290
3		SF	8424
4		NF	8168
5		NO	5380
6		EF	5345
7		SO	5231
8		WF	4971
9		EO	3656
10		WO	3255
11		TO	2014
12	SF		1357
13	NF		1237
14	TR		994
15	EF		864
16	NO		774
17	WF		761
18		FR	732
19	SO		643
20	WO		472
21	EO		471
22		CN	300
23		TR	240
24	CO		193
25	CN		100
26	TO	TO	86
27		CO	73
28	TO	TR	71
29	TO	SF	43
30	TO	NF	41
31	TO	NO	34
32	TO	WF	29
33	TO	CN	24
34	TO	SO	23
35	TO	FR	22
36	TO	EF	20
37	TO	EO	20
38	FR	TO	19
39	FR	SO	17
40	FR	EO	16
41	TO	WO	16
42	FR	FR	15
43	FR	NO	15
44	FR	NF	10
45	FR	SF	9
46	FR	WO	9
47	FR	WF	8
48	WO	FR	8
49	NO	FR	7
50	NO	NO	6
51	NO	TO	5
52	SF	TO	5
53	TO	CO	5
54	WO	WO	5
55	NF	TO	4
56	SO	FR	4
57	EF	TO	3
58	EO	FR	3
59	FR	TR	3
60	NF	NF	3
61	NF	SF	3
62	NO	SO	3
63	SF	SF	3
64	SF	SO	3
65	TR	TR	3
66	CN	TO	2
67	EO	EF	2
68	EO	EO	2
69	FR	CN	2
70	FR	EF	2
71	SF	FR	2
72	SF	NF	2
73	SO	SO	2
74	SO	TO	2
75	TR	TO	2
76	0		1
77	CN	WF	1
78	CO	SO	1
79	EF	FR	1
80	EF	WF	1
81	EO	TO	1
82	EO	WO	1
83	NF	NO	1
84	NO	EO	1
85	NO	SF	1
86	SF	NO	1
87	SF	WF	1
88	SO	EF	1
89	SO	NF	1
90	SO	NO	1
91	SO	SF	1
92	TR	CN	1
93	TR	EO	1
94	TR	FR	1
95	TR	NF	1
96	TR	NO	1
97	TR	SF	1
98	TR	SO	1
99	WF	SO	1
100	WO	EF	1
101	WO	EO	1
102	WO	SF	1
103	WO	SO	1
104	WO	TO	1

[agude]

I think its:

{N,S,E,W}X is direction, and X{O,F} is ON,OFF-ramp.

I think TO is "To..." and FR is "From...". I don't know what CO and CN are, possible "Collector" and "Connector"? No idea what TR is...

Here is just primary_ramp:

	primary_ramp	total
0		5399803
1	TO	61029
2	FR	25415
3	SF	1374
4	NF	1248
5	TR	1006
6	EF	869
7	NO	797
8	WF	762
9	SO	655
10	WO	490
11	EO	480
12	CO	194
13	CN	103
14	0	1

[agude]

This (https://iswitrs.chp.ca.gov/Reports/jsp/samples/RawData_template.pdf) says the values are:

NO: NB On Ramp
NF: NB Off Ramp
SO: SB On Ramp
SF: SB Off Ramp
EO: EB On Ramp
EF: EB Off Ramp
WO: WB On Ramp
WF: WB Off Ramp
To
From
Transition
Collector
Connector
blank 

So I'd guess TR is "Transition".