Try an engineering school/college in your area. Though they problably don't use it anymore, someone will have a copy. Call the civil eng department and ask to speak to the head of the Transportation department and they will refer you to a TA or professor that can help.
Roundabouts can be used for traffic calming by reducing speeds but will not serve as a traffic deterant. Also, roundabouts do not actually lower accident rates, but rather severity of accidents. The geometry prevents cars from crossing perpendicular to each other, thereby...