* Significantly more than $1.7m to build a roundabout, vs $40,000 for one that can be installed on existing infrastructure.<p>* Adding roundabouts requires more land, which is in tight supply in a built-up city like Seattle. I don&#x27;t think shaving the corners off of buildings is going to go over very well.<p>* As I&#x27;ve noted, the buildup of the cameras is very recent. The traffic light data you cited is over a year old. They&#x27;re creeping into the side streets now.<p>* Nobody needs a study to see the obvious improvements possible in cases I cited.<p>* Given the desire of the government to install cameras everywhere on the roads, the cost of them is going to be there with or without roundabouts.<p>* Far friendlier to pedestrians? How is that possible when cars don&#x27;t stop? I&#x27;ve crossed roundabouts in England as a pedestrian. It involves pushing a button and a traffic light turns red so you can cross. I.e. the traffic lights are still there!<p>* In Romania the roundabouts also had traffic lights for the pedestrians, as well as pedestrian tunnels under the intersection. That can&#x27;t be inexpensive.<p>* I can see a roundabout as cost effective in a rural area where land is cheap and there are few pedestrians. In a builtup city, not so much, as they&#x27;d be massive and expensive construction projects. A $40,000 box can be installed instead with no disruption and immediate improvements. Sounds like a winner to me.