Roundabouts do reduce serious accidents, but increases minor accident and incidents of road rage increase.
The design standards say only use them when there is equal traffic flows on all approaches, this not at existing roundabouts,
The single lane roundabouts require large trucks to climb onto the center of the circle.
Roundabouts are not worth the dollars.
A properly designed and installed traffic signal is a much better fix. Yes, that includes the installation of flashing lights warning of signal on highways of 35 MPH and above.