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Capacity Analysis of Interchange Ramp Terminals Final Report (1997) / Chapter Skim
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CHAPTER 4 Conclusions and Recommendations
Pages 119-122

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From page 119...
... Upstream input capacity cannot exceed the total downstream service capacity available, and may be less than this capacity if demand starvation on short links occurs. In addition to phase capacity, signal offset during oversaturation is the most important factor in the allocation of downstream capacity to upstream phases.
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From page 120...
... In the context of junction type (e.g., single-point urban diamond, diamond interchange, etc.) , the saturation flow rates for the left turn movements at single-point urban interchanges are more nearly equal to those of through movements because ofthe large turn radii associated with this interchange type.
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From page 121...
... and level alignments, and have traffic volumes that are relatively high, reflecting those found during peak demand periods. It is recommended/hat the equations providedin Chapters be used to estimate the saturation flow rate, start-up lost time, green extension, end lost time, and lane utilization factor.
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From page 122...
... Implementation of the PDX Model features into internationally recognized computer signal timing optimization programs, such as the PASSER programs, TRANSYT and SIDRA, is highly recommended. None currently handle oversaturated conditions very well, and the addition of the PDX Model features would give the programs the capability to reliably estimate queue spillback elects on saturation flow and elective green fume.
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Key Terms

  • flow rate
  • lost time
  • effective green
  • lane utilization
  • pdx model

  • flow rates
  • queue spillback
  • phase capacity
  • prevailing saturation
  • utilization factor

  • signal timing
  • green time
  • traffic pressure
  • downstream queue
  • traffic movement

  • input capacity
  • model features
  • significant effect
  • factors based
  • utilization factors

  • lost times
  • subject phase
  • upstream input
  • travel distance
  • overflow downstream

  • downstream receiving
  • capacity available
  • improved using
  • impediments due
  • time increases


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