On TOPS lists the train reporting code is actually 10 digits long. I know that digits 3,4,5,6 are the headcodes we usually see. I believe the last 2 are used to identify the day the train originally started in service as lists I have seen today have most of these ending in 05.
A 10 character Train Identity is used in TRUST messages to identify an instance of a schedule running on a particular day of a month. This data is composed of the following:
- First two digits of the originating STANOX
- The Train Reporting Number
- '1', '2', '3', 'C', 'M', 'N' or 'O'
- A letter representing the departure time from the origin (see below)
- Two digits indicating the day in this calendar month the train runs
...and the unexciting table:
Between Letter Between Letter
0000-0059 0 1230-1259 L
0100-0159 1 1300-1329 M
0200-0259 2 1330-1359 N
0300-0359 3 1400-1429 O
0400-0459 4 1430-1459 P
0500-0559 5 1500-1529 Q
0600-0659 6 1530-1559 R
0700-0729 A 1600-1629 S
0730-0759 B 1630-1659 T
0800-0829 C 1700-1729 U
0830-0859 D 1730-1759 V
0900-0929 E 1800-1829 W
0930-0959 F 1830-1859 X
1000-1029 G 1900-1959 Y
1030-1059 H 2000-2059 Z
1100-1129 I 2100-2159 7
1130-1159 J 2200-2259 8
1200-1229 K 2300-2359 9