From Festipedia, hosted by the FR Heritage Group

It is not envisaged that this section will cover culverts, only locations where major structures are involved.

There are two categories of bridge. One that carries something over the railway, designated OB for Overbridge, and one that carries the railway over something, designated UB for Underbridge.

Bridges on the FR line are not numbered.

Bridges on the WHR line were lettered sequentially from Caernarfon to Dinas Junction, and numbered sequentially from there to Porthmadog during the construction period. However for operational purposes they have now been marked with new numbers based on distance from Caernarfon, in kilometres to two decimal places, referred to 20.00 at Caerrnarfon, prefixed OB or UB as appropriate. For full explanation see Bridge Numbering On The WHR. However this does not explain why the bridge at Caernarfon also has the number 1...

Festiniog Railway (in order from Porthmadog)

Welsh Highland Railway (in order from Caernarfon - Construction numbers shown. Operational numbers may be added later)

See also[edit]