Episode XIV: The Bridge of Caledonian Doom was uploaded on July 31, 2014 and is the fourth episode of the second season.
D199 attempts to help Donald and Douglas after having his diesel tank drained of beer, but they Scottish Twins stubbornly refused do to them not trusting him. However, when they later got stuck on a collapsing bridge, he came to their rescue. Although he was able to save the twins, the bridge finally collapsed under him and D199 fell to the water below. Donald and Douglas were happy that he saved them, but felt guilty for being so rude to him. D199 was eventually fished out of the river and was awarded by the Fat Controller by being purchased for the North Western Railway and given a new name, which was Ted.
- Donald and Douglas
- Sir Topham Hatt
- Trevor (cameo)
- Fergus (cameo)
- Scruffey (cameo)
- Bill and Ben (cameo)
- Diesel 10 (cameo)
- Diesel (cameo)
- Paxton (cameo)
- Derek (cameo)
- Sidney (cameo)
- Rosie (cameo)
- Daisy (cameo)
- Carson0802200: Donald and Douglas
- EnterprisingEngine93: Edward
- Knapford Productions: Bear
- Thomas1Edward2Henry3: Everyone Else
- This episode continues where Old Reliable left off. The episode was also produced concurrently with that said episode.
- The title is a parody of the "Bridge of Khazad-Dum" from the Lord of the Rings: The Fellowship of the Ring.
- This is the first episode to feature Carson08022000 as Donald and Douglas.
- Music from the movie Star Wars Episode I: The Phantom Menace is used.