A modern roundabout with more than two lanes often has significant traffic and safety problems due to the weaving and merging of vehicles. This paper proposes a new method of traffic signal control that minimizes these problems by eliminating the conflict points and weaving sections with different traffic flow rates on each approach. In this method, a second stop line beside the first stop on the approach is set exclusively for the left turn traffic on the circulatory roadway. Traffic signals are installed before each stop line to eliminate the conflicts between the traffic flows on the approaches and the left turn traffic flows on the circulatory roadway. Left-turn vehicles on the circulatory roadway will stop before red signals to avoid weaving. Equations are derived to compute the signal cycle length and the green time for each traffic flow, considering the limited queue on the circulatory roadway. Capacity and delay are also formulated to evaluate the roundabout's performance. This traffic signal control has been successfully applied to a modern roundabout in Xiamen, China. The signal timing scheme was computed with the proposed equations, as well as the capacity and delay. The average delay of each vehicle decreased by 20 seconds and the roundabout capacity increased 72.1% following the improved traffic signal control method.


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  • Accession Number: 00989072
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Apr 11 2005 12:00AM