Macski:
Why do they plant these, I know they may look nice but you can’t see things coming around the roundabout!
Roundabouts were initially invented and implemented to aid the flow of traffic, and the reason trees are placed in them is because trees produce oxygen and roundabouts produce a lot of pollution, hence air quality is relatively held in check. 
Over here there are a number of cities that have a traffic light controlling vehicles entering a freeway, Now that’s a pain, how can you enter at highway speed from a standing start ■■