The traffic button just scans for the next station that plays traffic info 'regularly'. It does not guarantee getting traffic info 'right now'. (And some stations that it chooses may not be having traffic info for a long time, for example, if I hit it at noon, it might take me to a station that only does traffic during the morning and afternoon rush hours.)
Thanks for the link, by the way. Very informative. Looking at the 'Features' page, what I can deduce is that the Prius displays the following in my area:
Primary Feature 2: Program Service Name (PS). This appears to be where call letters or a short 'name' are transmitted. All of my stored stations seem to transmit this. This is the 8-letter 'name' that appears in the button or ID field.
Primary Feature 4a: Travel Program Identification (TP). This is what I am assuming is 'on' on the channels that tune when I use the 'TRAF' button.
No other primary features seem to be in use. Secondary features in use in my area are:
1. Program Type (PTY). This is what lets you use the 'genre' button to change types of music, and have it find that type of station for you. (Although in my area, some are very loosely defined. I have a country station listed as 'Pop', and a R&B/Rap station listed as 'Easy Listening'.)
2. Decoder Information (DI). This simply tells if it's in stereo or not. Although the Prius might just show what it is actually playing, not what the sender is sending.
7. Radiotext (RT). This appears to be the 48-character data that I see local channels using to display song information. This appears to be what triggers the 'MSG' button and the 'message' screen. I have only seen this in use by music stations, and now that I think about it, only stations owned by a single conglomerate. (Entercom.) Although I haven't paid too much attention to other stations, since the only two commercial stations I listen to on a regular basis are both Entercom. This field appears to load slowly, and 'overwrite' the button and ID field as it receives it. Once a complete message has been received, it makes the 'MSG' button available, and will then display the entire message in the message screen. But even if I'm driving, or when I'm not in the message screen, this data 'scrolls' in the station button and the station ID field.
Here's a short video clip of what I mean.
http://homepage.mac.com/ehurtley/rds.mpg (1.3MB 160x120 MPEG-1 file recorded on my digital still camera.) When it first starts, it's a closeup of just the buttons. All six have 'names' associated with them, apparently from 'primary feature 2'. Button 4 is 'scrolling' the name of a song (but not the song that's playing,) as is the 'station ID' field at the top left. When I go into the message screen, the same message is shown there as is scrolling (still) in the 'station ID' field. I then leave the message field, and switch stations. Data starts 'scrolling' in both the button and station ID field, which, when I then go to the message screen, shows up there.
Is this not how it works for the rest of you?