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Capacity and Level of Service at Unsignalized Intersections Final Report Volume 2 - All-Way-Stop-Controlled Intersections (1996) / Chapter Skim
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Chapter Two. Previous Work
Pages 5-10

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From page 5...
... proposed a capacity model for AWSC intersections based on saturation headway values for two cases, one In which the driver faced another vehicle on the opposing or conflicting approaches and one In which He driver faced no over vehicles. He measured values of 4.0 seconds and 7.6 seconds for these two cases, based on a study of three sites in Chicago conducted during periods of continuous queuing.
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From page 6...
... After several years of use by the traffic cogineeiing community, Ellis method was published as part of the 1994 - atetothe HCM as the approved procedure to determine the capacitor of an AWSC intersection. The 1994 HCM Update describes the basis for traffic operations at an AWSC intersection: The headway between vehicles departing from a STOP line of an AWSC intersection is a function of the conditions present on the other intersection approaches.
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From page 7...
... .. ~ _ ~ Capacity ofthe subject approach Vp, Proportion of intersection volume on subject approach VpO Proportion of intersection volume on opposing approach ~Number of lanes on subject approach L Number of lanes on opposing approach LTpo Proportion of volume on opposing approach fuming left RTpo Proportion of volume on opposing approach tuning right LT,,, Proportion of volume on conflicting approaches turning left RTp, Proportion of volume on convicting approaches t~= The delay formula now used In the 1994 HEM Update, given In Equation 4, Is based on We volume/capacity ratio, v/c.
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From page 8...
... To more accurately assess He effects of opposing and conflicting vehicles, eight cases were proposed. The saturation headways measured during the pilot study were classified into these eight cases and are listed in Table 9.
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From page 9...
... ~ . 1 I No odes vehicle | No other vehicles 1 3.0 1 3.0 l 2 One vehicle No other vehicles 4.7 4.8 3 No other vehicle One vehicle from the left approach 5.7 5.9 4 No over vehicle One vehicle from We light approach 5.7 5.6 S No other vehicle One vehicle from both the left and right approaches 7.3 7.1 6 One vehicle One vehicle from the left approach 7.3 7.2 7 One vehicle One vehicle from the right approach 7.4 7.3 8 One vehicle One vehicle from both the left and right approaches 9.1 9.2 Notes: The values are based on the mean ofthe mean values measured for each ofthe 13 subject approaches of this pilot study.
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From page 10...
... Table 11. Saturation Headways for Passenger Cars and Trucks 1 2 3 4 S 6 7 8 3.2 4.8 S.7 S.7 7.4 7.2 7.6 9.2 798 758 355 341 521 624 668 694 4.6 S.9 7.6 8.7 8.3 7.9 7.9 11.6 15 19 3 12 IS 17 18 Total 64 4759 7 g , , , , .
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Key Terms

  • saturation headways
  • subject approach
  • subject vehicle
  • conflicting vehicle
  • approach vehicle

  • awsc intersection
  • opposing approach
  • opposing vehicle
  • conflicting vehicles
  • awsc intersections

  • hcm update
  • headway data
  • vehicle bom
  • conflicting approaches
  • capacity equation

  • passenger cars
  • directional movement
  • headway values
  • nearly equal
  • ofthe subject

  • anthony richardson
  • conditions faced
  • driver faced
  • heavy trucks
  • headway measurements

  • transportation research
  • intersection approaches
  • significant difference
  • whence subject
  • intersection volume


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