This brings to mind the Piaggio Group 3-wheeled scooters.
Piaggio MP3:
Gilera Fuoco:
Let's not kid ourselves that the Gilera isn't ugly as hell, but the Piaggio comes with smaller engines, a hybrid and a wider front-track model that can be ridden on a car licence. I'm getting rid of my 250 soon so I might save up for one of these. Might make a really good base for a streamliner project - inability to fall over could facilitate the implication of more enveloping bodywork.