It's very motivating; the "Brooms" and "Eeeekkks" all around the room act as a constant reminder to include the capital letter and full stop and do the check at the end. There was a day or two of silliness, but now they just get on with it. Occasionally it goes a little quiet and I have to ask, "Aren't there any buses running today?" before normal service is resumed.
We have had interactive whiteboards installed and this works very well for modelling writing. I start my bus (Brooom!), write my sentence, screech to a halt and then the whiteboard comes into its own. To check the passengers I use the handwriting recognition feature. It's nearly 100 per cent accurate if I write carefully and less so if I don't, so the children help me check whether the computer has correctly identified all the words. If we're all happy with the result... "Brooom!" Next sentence.
I'm already thinking ahead. Commas? A little indicator noise to show a slight change of direction. Question marks? Obviously, a "Beep, Beep" noise. ("What are you playing at?") Exclamation mark? Probably the sound of a little crash! All aboard! Any more fares? Broom, broooom...
Year 3 class-teacher, St Nicholas Junior School, Dereham, Norfolk