Bertie the Bus is a small red bus

Bus

A bus is a road vehicle designed to carry passengers. Buses can have a capacity as high as 300 passengers. The most common type of bus is the single-decker bus, with larger loads carried by double-decker buses and articulated buses, and smaller loads carried by midibuses and minibuses; coaches are...

 character from The Railway Series

The Railway Series

The Railway Series is a set of story books about a railway system located on the fictional Island of Sodor. There are 42 books in the series, the first being published in 1945. Twenty-six were written by the Rev. W. Awdry, up to 1972. A further 16 were written by his son, Christopher Awdry; 14...

 books by the Rev. W Awdry and who also appears in the spin-off children's television series Thomas and Friends.
Bertie first appeared in 'Thomas, Terence and the Snow', a story in Tank Engine Thomas Again (published 1949). His first major appearance came in the next story, 'Thomas and Bertie', in which he had his famous race with Thomas.