Why are there NO Roundabouts on Missoula’s Reserve Street?: An Informational Guide 2nd Edition – US Dept. of Transportation

A roundabout is an intersection that uses a circular junction instead of stoplights or stop signs to manage traffic flow. Instead of every car stopping, they enter the roundabout slowly, and traffic moves almost continuously.

Systematic, well-designed research provides the most effective
approach to the solution of many problems facing highway
administrators and engineers. Often, highway problems are of local
interest and can best be studied by highway departments individually
or in cooperation with their state universities and others. However, the
accelerating growth of highway transportation develops increasingly
complex problems of wide interest to highway authorities. These
problems are best studied through a coordinated program of
cooperative research.

In recognition of these needs, the highway administrators of the
American Association of State Highway and Transportation Officials
initiated in 1962 an objective national highway research program
employing modern scientific techniques. This program is supported on
a continuing basis by funds from participating member states of the
Association and it receives the full cooperation and support of the
Federal Highway Administration, United States Department of
Transportation.