and they want to slow cars down without having to make them stop
Round-abouts are crap I hate them, they are VERY dangerous to cyclists.
I have a two lane round-about at the top of my street and it has 5 roads meeting at one little circle. I have seen cars plough straight through at 60kph/40mph, if drivers can't give way to other cars what hope is there for cyclists. If the round-about has good visibility to the right, most cars will not slow at all. The they take a quick glance to look for other cars and proceed like there is no intersection at all.
My home state is covered with these things, there are 9 in my suburb, in the space of 2miles.
CHEERS.
Mark
Moving in 34 days and counting!