Bertie is a red bus who works near Thomas' Branch Line.
Bertie was first seen taking Thomas' passengers after he got stuck in the snow. He later challenged Thomas to a race, and they have become the firmest of friends.
Later, he began to complain about Thomas being late due to the Main Line Engines being late at Elsbridge due to work on The Viaduct.
In 2006, he was shown to take workmen to Anopha Quarry with Toby, but couldn't get past the front gate, and one morning he was ill, and Toby had to take some of the workmen on Henrietta's balcony. For this reason, Victoria was restored to help Bertie and Toby with the workmen.
Bertie is friendly and ready to help anyone in need, but can't resist teasing Thomas about being slow.
Bertie is painted in the common red livery of buses in the United Kingdom, mostly famously used by London Transport.
- Season 1 - Edward Gets it Right, Harold and the Flying Climbers (cameo), and Thomas' Three Cheers
- Season 2 - Slow Coaches, Mike and James, Stepney's Journey Out (cameo), and Flying Scotsman Departs (cameo)
- Season 3 - Old Slow Coach, The New Controller (cameo), Jack and Alfie Swap, Bertie's Foggy Day, and Unique Stafford
- Season 4 - Thomas and Algy, Flora's Tram Coach (cameo), Special Engines, Saved by the Belle, and George and Buster
- Season 5 - Sodor Snowstorm (cameo), Snow Rescue, Nigel (mentioned), Silver Steam, Sodor Wash Day (does not speak), and Stanley's Branch Line
- Season 6 - James and the Royal Train and Edward and the Express
- Season 7 - Thomas and Toad