I think roundabouts with three entry lanes are growing out of favor. Roundabouts with three entry lanes were constructed as part of the US41 project in Wisconsin. From my understanding, Wisconsin has no plans to design new roundabouts with three entry lanes moving forward. DaBigE might have more information regarding this based on some posts I've read of his.
As far as I know, we're designing the last roundabout in Wisconsin that will have 2, three-lane entries. Yes, Wisconsin does now have a phobia/moratorium of any additional roundabouts with three-lane entries (with the exception of one region). Other states seem to be sharing the trepidation as well. We've worked on a few three-lane designs for other states, but many have ended up being scaled back. In many cases, three lane entries aren't needed for a long time, and depending on the analysis software/skill of the analyst, may never be needed. Attempting to design for 20-year forecasts can be very tricky/dangerous, especially for new developments.
There is a growing belief that many roundabouts are being over-designed, which leads to larger than necessary designs. The problem in the US is lack of reliable data (number of years of available of data), and correction factors that vary depending on what portion of the country you're in. If you read the WisDOT FDM section on roundabout design (
FDM 11-26 if you're interested), Wisconsin uses it's own critical headways and follow-up headway values for capacity analysis.
There's also big debate over how to handle trucks (semis - WB-62s, WB-67s): should they stay in-lane, and if so, where? Just on the entry (aka Case II)? Throughout the roundabout movement (Case III)? Neither (Case I)? That can also lead to larger than necessary designs > faster operating speeds > more crashes.
Am I surprised that the Wisconsin Department of Transportation funded a report that analyzed a roundabout with dissimilar before and after conditions? No. This is the same agency who designed these crash prone multi-lane roundabouts to begin with. To be fair, several of the roundabouts included in the report have similar before and after conditions. If you take out the results of the 25th Street & Canal roundabout, the remaining multi-lane roundabouts saw an overall increase in crashes.
All I am going to say on this is there's a lot of flaws that can be found in WisDOT's roundabout crash studies (Phase III is set to be released later this summer).
The take-home message has been severe injury/fatal crashes have seen significant decreases. Fender-benders (aka PDO crashes) have gone up significantly in multilane roundabouts. Having read through many crash narratives, the majority have been attributed to failure to yield or improper lane usage). The stupid maneuvers people try to pull...it's almost so common it ceases to amaze me any more.