CSX milepost prefixes in Waycross, Georgia, 587 miles south of Richmond on the branch to Montgomery, Alabama (which splits near milepost 548 in Jesup). Three-letter prefixes are used for minor branches of these branches, or minor branches off the mainline - for instance ANA is the northernmost branch of AN. Before the ACL merged into the Seaboard Coast Line Railroad in 1967, none of the prefixes had the initial "A". The letters "I" and "Q" were skipped, and double-lettered prefixes (like KK, which would be AKK post-1967) were not used. A is given to the main line from Richmond, Virginia to Port of
Three-letter acronym Three-letter acronym A three-letter acronym (TLA), or three-letter abbreviation, is an abbreviation, specifically an acronym, alphabetism, or initialism, consisting of three letters. These are usually the initial letters of the words of the phrase abbreviated, and are written in capital letters (upper case); three-letter abbreviations such as "etc." and "Mrs." are not three-letter acronyms, but "TLA" is a TLA (an example of an autological abbreviation). Most three-letter abbreviations are "initialisms": all the letters are pronounced as the names of letters, as in "APA" . Some are acronyms pronounced as a word; computed axial tomography, CAT, is almost always pronounced as