I had recently seen a State of Maryland highway map in which a mapping tool apparently was used to measure a "BLOC" (Bicycling Level of Comfort) score for various sections of roadways. The BLOC score considered parameters such as traffic volumes and speed, roadway width, etc. It looks like they used the formula applied by this application to set standards to various roadways as to suitability for cycling.
The way I see it, the formula provides a blend of some objective information to give some clue as to what a cyclist might expect on various roads; I did not have an opportunity to ride any of the designated roadways when back there, so I don't know how the mapped rankings relate to actual "on the road" experience.
Here's the link to a related web page:http://www.sha.maryland.gov/OPPEN/BLOC_Washington.pdf
Their staff may have some insights to share on what they had considered for the development of this information, standards, etc. I noticed two phone numbers on their websites - 410-545-5674 and 410-545-5656. Maryland's approach to the roadway designations may or may not be similar to what you are looking for, but perhaps this will help.
Good luck with the project (I've been "eyeballing" your area recently as an area for a possible multi-day bike tour!).