Deviation Site -1
(Note - Site -1 should be shown on the map a little further south)
The Deviation sites were initially numbered starting with 1. It was then realised that two other sites nearer Porthmadog were needed so these were numbered 0 and -1, the latter involving widening the top end of the cutting south of Dduallt station site so that a passing loop could be installed with the points as far south as possible.
FRM37 (Summer 1967) recounts "Just after Easter the top end of Dduallt cutting was blasted, in preparation for the new passing loop. Known as Site -1, the main line was cleared again within a fortnight and the widening is now well in hand". There had been a footbridge over the line at this point but this work removed its eastern abutment.
More information at Numbered Sites.