Regarding roads named as letters, I agree that surrounding the capitalized letter with single quotes will look the best as Alan said. I have yet to retest for the various test from the list for the letters, N, E, S, and W, however multiple Wazers have indicated recently that the result are now different that what is shown in the list.
Using a period after a letter may lead to confusion, as it looks like a standard cardinal direction abbreviation, as Jason said.
However using periods with multiple letters, such as A.T.T. or N.Y.C. to get the abbreviation pronounced as individual letters should be fine, if it really is working that way universally now.
One problem is that we have found in the past that many factors affect the TTS results.
The position of the abbreviation relative to other words, punctuation around it, capitalization, and the various combinations of those factors.
When list here was created, I used a space a forward slash and a space around every abbreviation, with multiple abbreviations per test segment. We expected a forward slash to produce a pause, as Waze said it would be any easy change. Since it did not happen as soon as we hoped, the TTS results were very hard to understand without any pauses. Another editor, jenncard, was helping at the time with the project, and created a test rig of her own with each abbreviation with a comma and a space. The results were much easier to understand.
Last spring I started to use her method for testing. Since that time however there has been suspicion that the comma may even cause a change in the results. Furthermore, it may be possible that ANY other words on a segment besides the abbreviation to be tested may create a different result.
If you look at the most recent entries in the list, you may notice that several test segments have created TWO TTS audio files which are actually different from each other. (On Android, one file is created with just the words in the segment name, and another file is created with the segment name prefixed with the word "at".)
A few examples:
- The abbreviation "RR" for "Rural Route", says the letters "ar ar" in one file and "Rural Route" in the other.
- The abbreviation "Cent" for "Center", say "Cent" in one file and "Center" for the other.
- Several abbreviations for "Parkway", say the letters for one file if the abbreviation is capitalized , and say "Parkway" for the other file.
- While testing "SH-123" as am abbreviation for "State Highway 123", one file said the letters and the numbers "one hundred twenty-three", where the other file said the letters and "one two three".
And in one case were I was testing the abbreviations "boro, par, ph" for Borough, Parade, and Parish, I had TTS results that said "borough par pea-aitch", and the other file said "borough parade phone".
When "ph" was tested again by itself, the results were the letters "pea-aight" for both files.
Testing for every possibility is a bit overwhelming at this point.
RC: Great Lakes - IL, IN, MI, OH, WI
AM: NW OH, NE IN, & SE MI
Verizon: Galaxy S4 w/ Android 4.3 & iPad "3" w/ iOS 7.1