Roundabouts

Sign Roundabouts are circular-flow intersections that have proven to move traffic through an intersection at a steadier rate of speed than a conventional intersection, as well as reduce the accident severity for crashes that occur in the intersection. In a roundabout, traffic flows counter-clockwise and the traffic entering the roundabout must yield to the traffic currently in the roundabout.
Tips for Driving a Roundabout
  • Choose the appropriate lane before entering
  • Slowdown
  • Yield to pedestrians at the crosswalk
  • Yield to traffic in the roundabout
  • Merge into the roundabout when traffic is clear
  • Proceed in correct lane until you have reached your exit
  • If you missed your exit, proceed around the roundabout until your exit arrives
  • Signal right blinker, indicating the intent to exit roundabout
  • When exiting, yield to pedestrians at the crosswalk
  • DO not STOP IN ROUNDABOUT AT ANY TIME
Grand and Shiloh

Conflicts at Standard Intersections vs. Roundabouts

Roundabouts are designed specifically to be safer intersections than conventional intersections. Roundabouts have fewer conflict points in comparison to conventional intersections. The potential for hazardous conflicts, such as right-angle and left-turn head-on crashes is eliminated with roundabout use. The images at right depict potential conflict points of a conventional four-legged intersection, and the same for a roundabout.

The circular nature of the roundabout requires drivers to slowly traverse the roundabout’s curves. This allows drivers more time to react to potential conflicts, while also limiting the severity of any crashes. The decreased speeds and severity typically leads to decreased injury-related accidents.
Conflicts comparison
Drawbacks of Roundabouts
When designed and constructed correctly, roundabouts are extremely effective at calming traffic at major intersections. By design, they can lower speeds, provide arterial access with minimal conflict points, increase efficiency, and most importantly, decrease severe crashes. However, there are some drawbacks that prevent the use of roundabouts at every intersection. These drawbacks include the following:
  • Pedestrian crossing are not controlled with signal operations
  • Maintenance of center roundabout island
  • Right-of-way limitations (overall size of the intersection is larger than signals)
  • Initial cost (primarily due to the right-of-way purchases needed)
  • Interaction with nearby traffic signals
Helpful Links
ROUNDABOUT PAMPHLET
/DocumentCenter/View/3754

ROUNDABOUT VIDEO
/DocumentCenter/View/3772

ROUNDABOUT ANIMATION BY OURSTON ROUNDABOUT ENGINEERING
http://www.ourston.com/resources/educational-tools/animations/four-leg.html
Billings Roundabout Locations
  • Ironwood Dr and Woodcreek Dr
  • King Avenue W and Olympic Boulevard
  • King Avenue W and Dannell St
  • North 27th St and Airport Road
  • Shiloh Road and Zoo Dr
  • Shiloh Road and Hesper Road
  • Shiloh Road and Knife River Entrance
  • Shiloh Road and King Avenue W
  • Shiloh Road and Monad Road
  • Shiloh Road and Central Avenue
  • Shiloh Road and Broadwater Avenue
  • Shiloh Road and Grand Avenue
  • Shiloh Crossing Boulevard