Impact of Turning Lane Storage Length and Turning Proportions on Throughput at Oversaturated Signalized Intersections

During oversaturated conditions, common objectives of signal timing are to maximize vehicle throughput and manage queues. A common response to increases in vehicle volumes is to increase the cycle length. Because the clearance intervals are displayed less frequently with longer cycle lengths and fewer cycles, more of the total time is used for green indications, which implies that the signal timing is more efficient. However, previous studies have shown that throughput reaches a peak at a moderate cycle length and extending the cycle length beyond this actually decreases the total throughput. Part of the reason for this is that turning traffic that leaves the through lanes creates gaps in traffic that reduce the saturation flow rate within each lane. There is a relationship between the proportions of turning traffic, the storage length of turning lanes, and the total throughput that can be achieved on an approach for a given cycle length and green time. This study seeks to explore this relationship to yield better signal timing strategies for oversaturated operations. A microsimulation model of an oversaturated left-turn movement with varying storage lengths and turning proportions is used to determine these relationships and establish a mathematical model of throughput as a function of the duration of green, storage length, and turning proportion. The model outcomes are compared against real-world data.


  • English

Media Info

  • Media Type: Web
  • Features: Figures; References; Tables;
  • Pagination: 26p

Subject/Index Terms

Filing Info

  • Accession Number: 01764364
  • Record Type: Publication
  • Report/Paper Numbers: TRBAM-21-02984
  • Files: TRIS, TRB, ATRI
  • Created Date: Dec 23 2020 11:27AM