text: It's not on the Transport Scotland list of trunk roads so think it's best to remain as primary. 
  
  There is discussion about it here: https://www.sabre-roads.org.uk/forum/viewtopic.php?t=38201
  
  I've seen elsewhere on the A91 road that some green signs have been changed to white, so presumably signs haven't been replaced.
  
  For example, there is a green sign here but the A905 is not trunk: https://www.mapillary.com/map/im/C0Oh7A1oQrYOOJgbX1ugfg