Earlier today I told about my encounter with an XL1.
By way of an encore I've just been in a diesel electric hybrid produced by the VW group. Not, sadly, an XL1 but rather one of these, a MAN Lion's City (yes, it's a stupid name) city bus. Uses super capacitors rather than batteries and does quite a lot of stop/starting. Quite a noisy beast if you sit in the back even in electric mode.