Effectiveness of speed measures to improve roundabout capacity “case study”

The objective of this study is to analyze the effectiveness of speed measures to improve capacity at the roundabouts under near saturation level. Alaska Department of Transportation and Public Facilities introduced measures of using speed humps on multilane roundabout to slow down vehicular traffic entering the roundabout which might improve safety and capacity. Spot speed, vehicular volume and queued data have been collected and analyzed before and after the speed measures. Results show use of speed humps bring insignificant change in speed profiles through the roundabout with little or no effect on capacity. In addition, measured and calculated queue lengths also show no significant change.