Series Number Id: UNKNOWN. Sheet number: parts of sheets 27 and 36. Fourth Army motor traffic circuits, Ypres Salient, January 1918. "[4th] Field Survey Coy R.E (8142) 26-1-18". Grey detail; overprint in red and blue. Two way traffic shown in red; single lorry traffic in blue., Location: Research Collections; Fonds: WW1 Trench Maps: France; Box number: PC19; envelope_number: 587.