Quasi sorted by rule number. Removed the that were confusing some systems. Incorporated comments received. Some indications and meanings. Derived from PennCentral practice, there is some, tho NOT complete commonality across RRs.
Transit systems tend to be even more individualistic.
While indications are similar and related, they need not be identical. CCOR means aspect used by Consolidated Code of Operating Rules, which governs many Western US railroads. Trying to keep this manageable. High Signal C Two Head High Signal. Approach next signal prepared to stop.