Parmelia sulcata

On trees alongside the Arnhem-Nijmegen freeway in Arnhem across the Gelredome stadium. I've enjoyed trying to determine this one with the CTMS method, i.e. Compare The Mug Shots, with the books I recently acquired. Kenny Dorham jazz music on the stereo, and leafing slowly, amazed by all the pictures and specs. I first assumed this to be Parmelia saxatilis but visitor Xanthoria says it's P. sulcata and I'm sure he knows better! Thanks!