I've tried using the linked method to determine area that drains to stream vs drains to road. For some reason when I run the watershed tool on the the raster representing stream and road features, I get a lot of areas that have no data (drain to neither road nor stream). I'm not sure why this is happening.
Determining Upslope and Downslope from Line Features to Map Hydrologic Capture Zones
Picture: stream lines are in light blue, drains to stream in dark blue, road in white, drains to road in green.
This has the DEM as background.
This one has the Flow Direction Raster Behind.
at @Jon Filling the origional DEM then re running the watershed tool got me some more coverage as shown in this picture. New area is shown in yellow and rose.