Author: tom[at]compton.nu
[Added to the original trac issue at 9.06am, Monday, 28th July 2008]

Punted to Steve but (a) this is hard as layer can only really affect objects that are rendered in the same pass with mapnik and (b) it's not clear that this rendering is actually wrong as tunnels are deliberately rendered above some things in order to show where they go.

Author: SvenR
[Added to the original trac issue at 4.55pm, Sunday, 21st December 2008]

In my opinion, tunnels should be rendered above areas because otherwise one would not see the tunnels anymore, especially in cities with many buildings. But the rendering could be optimised, maybe the tunnel can be rendered less opaque, letting the background (building, water etc.) shine through slightly.

Author: steve8[at]mdx.ac.uk
[Added to the original trac issue at 8.49pm, Sunday, 11th January 2009]

This was done a couple of versions ago now.