A GpsPasSion forum member has posted an excellent piece on the state of live traffic reporting in the US, with historical background, a look at the various ways traffic is reported, and even a ranking of number of probes for the key players. Google tops the list BTW, thanks to their Android coverage. There are a couple of pieces missing (NAVTEQ sources, iPhone probe data sent back to Apple – and no, I don’t have the answers to those), but overall this is the best summary of its sort I’ve seen. There are a few shoes left to drop – Apple’s predicted mapping solution, the fact that Garmin will soon have a lot of probe data as their mobile apps take off, and (as the article notes) RIMs massive network of probes.
There’s also a lot of interest right now in TomTom’s newly announced HD Traffic, which is clearly not in the same league as their European system going by the same name. GpsPasSion has a write-up on this too, with some good information on data sources and the role played by their IQ Routes historical road speed database.