Bertie is friendly and ready to help anyone in need. However, he can be quite cocky and 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.
Bertie is based on an AEC Regal "T Class" London Country Area bus.