EFFECTS OF SIGNAL PHASING AND LENGTH OF LEFT-TURN BAY ON CAPACITY

A periodic scan computer simulation program was developed to investigate the effects of signal phasing and length of left-turn bay on capacity. After the simulation program was tested, inputs (phase sequence, volume, cycle length, and length of left-turn lane) were varied to evaluate their interrelationships under a range of conditions. Additional analysis was conducted by using a modified Poisson approach. The results show that, for a left-turn bay, traffic delay increases and signal capacity decreases when traffic interactions and flow blockages occur between left-turning and through vehicles. High left-turn volumes and short bay storage lengths experience the most severe reduction in capacity. We developed mathematical relationships between reductions in left-turn capacity and geometric and traffic conditions and provide design guidelines to minimize capacity reductions. Judicious selection of signal phasing reduces the loss in capacity to some extent, although all phasings can experience large losses under some geometric conditions. /Author/

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 95-101
  • Monograph Title: Highway capacity, traffic flow, and traffic control devices
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00183551
  • Record Type: Publication
  • ISBN: 0309026733
  • Files: TRIS, TRB
  • Created Date: Dec 3 1978 12:00AM