The bus belonged to CBeebies Radio, and was a hands-on project with lots of buttons to push and levers to pull. Each button or lever was themed to a certain CBeebies Radio show, story or song, such as No Such Town, Digi Tales, Cloud Nine, Jumble Bus, Granny Anne's Joke World, Cymbeline's Dream Workshop or others. Everything on the bus was free to press, and everything you heard came out of loudspeakers from each corner of the bus, so you can enjoy the imagination that sparks listeners' own.
I wish there was a CBeebies Radio bus in real life that visits primary schools and lets them press a button to listen to their favourite show from CBeebies Radio, or do creative writing activities based on the shows. It would be brilliant if they did that.