I was getting crazy elevation data on some segments of the Sierra Cascades (up to 60% gradient!) but didn't mind them, assuming that elevation of a road carved in a canyon could be off because the satellite reading was a few meters left or right. But then I was really puzzled by a very steep segment on the supposedly easy Eurovelo 6. Turns out that the elevation data refers to the terrain (obvious, isn't it) while the trail goes through a tunnel...

Anyone knows about a source that would provide road elevation? (or flag tunnels on a course)