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CE 578 Highway Traffic Operations

CE 578 Highway Traffic Operations. Lecture 21: Freeway Ramps and Ramp Junctions Diverge Areas. Objectives. Basic concepts Important variables Relate to merge areas. Basic Concepts. Volume v 12 Capacities Total departing Prior to deceleration lane Downstream legs

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CE 578 Highway Traffic Operations

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  1. CE 578 Highway Traffic Operations Lecture 21: Freeway Ramps and Ramp Junctions Diverge Areas Michael Dixon

  2. Objectives • Basic concepts • Important variables • Relate to merge areas Michael Dixon

  3. Basic Concepts • Volume v12 • Capacities • Total departing • Prior to deceleration lane • Downstream legs • Determine influence area flow density Michael Dixon

  4. Important Variables • LD • VR • VD • VU • V12 • VF • VFO Michael Dixon

  5. Important Variables (cont.) Michael Dixon

  6. Important Variables (cont.) Michael Dixon

  7. Relation to Merge Area Procedure • Estimate V12 using V12 = VR + (VF – VR)*PFD Michael Dixon

  8. Ramp Sequence Scenarios Michael Dixon

  9. Ramp Sequence Scenarios (cont.) • Ramps with no affect--- • Upstream on-ramp: • Downstream off-ramp: • Both Upstream on-ramp and Downstream off-ramp: • Use for LEQ of upstream on-ramp • Use for LEQ of downstream off-ramp Michael Dixon

  10. Capacity Comparisons Michael Dixon

  11. Capacity Comparisons (cont.) • Estimate and compare capacities (___________________________) • Maximum flow that can depart (upstream mainline capacity (___________) • Maximum upstream flow in lanes 1 and 2 prior to deceleration lane (___________) • Maximum flow on downstream lanes • (______________) • (______________) Michael Dixon

  12. Michael Dixon

  13. Determining LOS • Calculate diverge area density: DR = 4.252 + 0.0086v12 – 0.009LD • Use same LOS table Michael Dixon

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