Bertie is a red bus who works alongside Thomas' Branch Line. He is owned by Sodor Roadways.

Bertie is friendly and ready to help anyone in need. However, he can be quite cheeky and can even be boastful about himself, especially to Thomas, always joking around and teasing him about their races. He can sometimes be quite grumpy, as whenever he breaks down or gets stuck, he grumbles about it. He is always, however, easy-going and cheerful to everyone he sees. Unlike Bulgy, Bertie respects the railways and its engines, and serves as one of the many minds keeping the double-decker bus in line.