Well, I sort of wanted to put this in the general forum, since it couldn't be MORE about roads - but then again, it says HIGHWAYS.. =)
So, because of a personal side business of mine, I decided to crunch some numbers on how many unique road names there are in the U.S -- using the U.S. Census TIGER shapefiles and road data for each county available at census.gov.
At first, I had no idea how many counties there were and was going to do it over time manually - with maybe a bit of automation. How fast I realized that that would be a many-year project. So in fact I automated the entire thing from beginning to end and thought I'd share some of the results with you all.
First, the basic info... the road data is culled from the TIGER ftp site at ftp2.census.gov/geo/tiger/TIGER2010/ROADS/
The ROADS archives are mysteriously named, so part of the process was figuring out which county they referred to, which was listed in one of the xml files in the archive. The road names were listed in a large DBF file for each county. Most roads had multiple instances. I'm not really sure of the census mapping process or how these were determined, but apparently there were multiple segments of each road, possibly one per CDP (census designated place) so long roads that went through multiple towns, or roads that showed up in many towns (like say, Main St.) had many entries. I collected these into unique lists noting how many times each showed up in the list. I did this collation at the county level, then the state level, then nationally.
In total, there are
2,325,841 unique road names in the U.S. Maybe i'm dimwitted, but this is probably 5-6 times what my initial estimation was.
I don't really want to put up ALL of the data I collected publicly, but I made a document to share which lists the number of unique street names in every county in one tab, and in every state in another... feel free to download the excel file at
http://bh.polpo.org/RoadsTotal.xls -- to clarify, this doesn't mean no other county has that name - just that it's 'uniqued' per county, so in the count for say, Litchfield, CT - the number does not include multiple roads named Main St, but it DOES include Main St.
Now for just a taste of it... these are the top 30 counties sorted by number of unique road names -- as I said you can see the whole list above if this isn't enough for you:

and the bottom 30 (with Puerto Rico areas removed.. I left them in the full list):

Then, the 50 states (+DC) sorted by number of unique road names (also in the document):

And finally, how could this be complete without a list of the top 30 road names, by how often they appear in the census databases. Note: I removed the various versions of Main St and all the numbered streets, which aren't very interesting to see in a list like this..

Anyway, a monstrous amount of data to pore through (I have a folder of about 8 gigs worth of files related to doing this), but I needed to do it and also thought you guys might be interested. If you're curious about any further data, like about your county inparticular, or your road name, I'll be glad to share.. just pm me.
Thanks!