I've learnt that the system of referenda and initiatives has a long tradition in Oregon (more than 100 years).
We don't have such here - our 'parliamentary democracy' is though to work.
We do have (in our state as well as - similar - in all other states) in local (not state) level two different kinds of 'referenda' (one, changing a decission made by the local council, the other ordering the local council to act - the latter is on state level as well).
In nearly all cases, these ballots are on different days than any other election.
(For the first time ever, we'll have the election for EU-parliament and for local/county parliaments on the same day next: an idea by the governing conservatives which might give them some advantage.)