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Capacity Analysis of Traffic-Actuated Intersections Final Report (1996) / Chapter Skim
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3 INTERPRETATION, APPRAISAL AND APPLICATIONS
Pages 29-34

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From page 29...
... NETSIM also provides an alternative to the proposed analytical model for estimating delay and level of service at intersections. For relatively straightforward situations involving signalized intersections, the analytical model will be the preferred choice of many agencies because it is simpler to apply, it offers intermediate computational outputs, and it performs direct estimates of capacity for each movement.
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From page 30...
... Therefore, it is not possible to compare delays estimated by HCM-type analytical models directly with any delay value reported by NETSIM. Distribution of Gaps in Arriving Traffic A traff~c-actuated controller terminates a given phase whenever a gap appears at the detector that exceeds the allowable gap specified for that phase.
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From page 31...
... It will generate the optimized settings for controllers ranging from pretimed to volume-density actuated controllers. The optimum settings oft~m~ng parameters include minimum green time, maximum green time, unit extension time, minimum gap, time before reduction, time to reduce, added initial, and maximum initial for each phase.
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From page 32...
... There is, however, a lower limit to the range of unit extension times that can be modeled realistically. It is well known in practice that when the unit extension times are too short, premature terminations of a phase may result due to anomalies in the departure headways created primarily by lapses in driver attention.
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From page 33...
... The analysis of permitted left turns from shared lanes always poses special problems. The sern~empirical treatment prescribed for shared lane permitted left turns in Chapter 9 of the HCM does not lend itselfto the iterative timing estimation procedure described In this report.
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Key Terms

  • unit extension
  • stopped delay
  • timing plan
  • departure headways
  • net sim

  • nchrp project
  • hcm total
  • estimation procedure
  • extension times
  • analytical model

  • proposed analytical
  • timing estimation
  • green time
  • maximum green
  • shared lane

  • procedure described
  • hcm chapter
  • analytical models
  • produced timing
  • timing plans

  • saturation flow
  • permitted left
  • arrival distribution
  • average departure
  • signalized intersections

  • departure headway
  • studies reported
  • shared lanes
  • reasonable approximation
  • headway values


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