Apparently the Roadway Weather Information System is a Federally guided project.
I see the sensors along the interstates and state roads in my state of Wisconsin, and in the past been told the information flowing in from them was not generally available to the public.
I just had a new contact introduced to me for road information (another story, but not too interesting) and she put me in touch with the meteorologist for the state who has said that Wisconsin is working on making those data sources publicly available this summer.
In the interim, I did a quick search and found this one for Alaska, and while I've not had a chance to look about much, found you can click on a diamond and get a lot of current info about the data at that site. I hope most states have made or will make this open to the public, which will add to us being able to check around.
In general, the stations I've seen are of 'government quality' using RM Young and other sensors. I assume they get a little attention and calibration too.
http://roadweather.alaska.gov/iways/roadweather/forms/IndexForm.html
