(Sorry, this got long.....)

There's a roundabout that was put in close to me at a similar intersection--one road had fairly heavy traffic (beltway exit about a half mile in one direction; intersection with a road with I-95 access about a half a mile in the other direction). The cross road was generally not so busy, but has a university campus on one side so at certain times of the day and during basketball games it would have very heavy traffic. This is also a route with lots of cyclists--the Park and Ride lot near I-95 is a staging area for group rides, there's a popular mountain biking trail entrance to the state park across from that, and the residential area to the north has lots of rental housing popular with the university students who do, on occasion, ride bikes. Few to no pedestrains, though--no sidewalks on the main road, and although there's a bus line that comes through, there are no stops right in that vicinity. Pedestrians from the residential area going to the college do have to cross the road, however. Average daily traffic volume on the main road according to a 2010 county map is about 25,000, but a 2005 study I read said the *intersection* handles 12,000 cars a day. Not sure if the volume has increased that much in five years or if the other side roads take a lot of the cars before they reach the intersection. Probably something in between.

I *love* the roundabout they put in. In general I'm a fan of roundabouts--I like how they keep traffic moving and how it makes it so much easier to turn left whether you're on a bike or in a car. I like it that you don't have to sit there looking at the other drivers trying to figure out who got there first and who is to the right of who. I like how they generally decrease the speed of the traffic going through (no one just zips straight through like you get at a typical intersection--everyone has to slow to navigate the circle, but no one has to come to a complete stop except at the busiest times of the day) and that they essentially keep everyone moving in pretty much the same direction, which is just easier to navigate. And the research I've read also points out that when accidents do happen, they tend to be less serious--fewer people hitting others broadside and lower speed accidents overall. As a cyclist, I find that I can usually go through a roundabout without even pausing--if you're going right or straight, you can just get to the right and keep moving. Turning left requires a bit more attention, but I find it less hair raising than turning left in most other circumstances. I've never had a problem with drivers not noticing me when I'm cycling through a roundabout.

That said, the roundabout near me is NOTHING like the one they are proposing for your area. They kept ours with just one lane in each direction, not two like they are proposing for yours, and there are no extra ramps and no sidepaths and sidewalks like yours shows. That level of roundabout seems unnecessarily large for that intersection, given the nature and volume of the roads. I tend to agree with you that it will probably speed up the traffic going through, particularly for anyone turning right--they're just going to whiz through those ramps. I can't help but wonder if this is being put in in advance of a lot of development? Are they planning to put a shopping center in there somewhere, or some office buildings? Is there going to be a lot of increase in residential development and traffic? I just look at that plan and think that they must have a long-term plan to widen the roads to allow for a big increase in the traffic volume.