Saw that drivers in St Ives were complaining about running into a "car trap" on a busway, signed with around 14 signs and big red painted "Bus lane" on the road surface.
So I thought I'd check out my local one I pass heading home. Clearly a bit of local knowledge is required as the first signs that this is a no through traffic route (except busses) is a KM or so from the end of the road where we turn it, at which point it is NOT signen.
While admiring the new cycle expressway taking shape along the first bit, I checked for signage, there are 2 signs in advance of the trap, which is around 50cm deep, going in is a one way trip in a car, until a tow truck gets you out again.