Well …….. I strongly disagree with your statement that bringing OSM tags closer to Caltrans functional classification “makes OSM a less useful and consistent map.”  It is one hundred percent the opposite – it makes it more useful and consistent. Visually, it provides more refinement for driving directions, for map viewing at different zoom levels as the possible access roads get revealed as one zooms in closer. Zoomed out levels show the primary and secondary roads as general grids while zoomed in levels show the full connection from primary to secondary to tertiary to residential (and all other). Without showing all these levels as they are and therefore (worry about overclassification) the map becomes quite inaccurate and meaningless at higher levels and very inaccurate at zoomed in levels.

Actually it is a very good idea to have a 1:1 correspondence between OSM and Caltrans. Think about what the purpose of the OSM map is. 
If the purpose of the map is to have a drawing of how roads have been built, then using multiple classifications to describe a road’s physical characteristics is fine. But then lets not kid ourselves in trying to use it for directions either visually or through the directions option – they simply will never provide accurate or proper directions. It will definitely get you to a destination, but it will not be the true way to get there. So any third party app or website calling OSM as a map will not have very good info. As far as I know, anybody who looks at a map is interested in how a road can get you somewhere – not what that road’s physical characteristics are. If this is the purpose of the map – then this results in a very flawed map for the ability to actually be useful and accurate – this might be the state we are in.
If the purpose of the map is to be useful in providing directions, then functional classification like the way Caltrans has them are more important than classifications based on physical characteristics. The “functional” refers to how the road is used, not how it is built. It is not a “physical classification”.

As far as stumps go, for Figueroa is just that I didn’t yet finish going all the way to 105. As far as Grand, and Topanga Canyon goes, these are excellent examples of  true Functional classification. These are not errors – they represent how functional classification is used to guide traffic. For Grant, the change means that in that zone for the street – traffic should start or end there. It is not meant for through traffic for two points further apart. Therefore, traffic from far away will avoid this area. This effect is also applied for general area such a downtowns.


Frankly, I think that the Caltrans map should be the starting point for mapping. Use it first and only then make adjustments to it for local knowledge. Although keep in mind that the person with the local knowledge does not have the studies, the analysis and the overall view of the road network to truly make the best decision. Caltrans does. The current approach is - use the base OSM which is flawed, and then continue to make adjustment based on local knowledge. This will never truly advance the map in usefulness or accuracy.

As far as the trunk classification goes, I still think that no road should be a trunk if it has sidewalks or allows bicycles. OSM does not even allow you to include “Add field: Bike Lanes” for a trunk classification. Which make sense. A road with bicycles on it, should not be a trunk.

Take care