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CE 578 Highway Traffic Operations

CE 578 Highway Traffic Operations. Freeways Merge Influence Areas. Objectives. Estimate flow entering influence area Estimate capacity and determining LOS Special cases (next class). Flow Entering Influence Area (V 12 ). V 12 = P FM * V F 4-lane freeways (P FM = 1.0)

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CE 578 Highway Traffic Operations

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  1. CE 578 Highway Traffic Operations Freeways Merge Influence Areas Michael Dixon

  2. Objectives • Estimate flow entering influence area • Estimate capacity and determining LOS • Special cases (next class) Michael Dixon

  3. Flow Entering Influence Area (V12) • V12 = PFM * VF • 4-lane freeways (PFM = 1.0) • 6-lane freewaysmore complex • 8-lane and 10-lane freeways Michael Dixon

  4. Flow Entering Influence Area (V12): Choosing the PFM Equation • four-lane: PFM = 1.0 • eight-lane: only one choice • ten-lane: only one choice • six-lane: See Exhibit 25-6 Michael Dixon

  5. Flow Entering Influence Area (V12): Choosing the PFM Equation Michael Dixon

  6. Flow Entering Influence Area (V12): Choosing the PFM Equation (cont.) • Only an issue for six-lane freeway sections • On-ramps do not affect V12 • If only on-ramps are involved Eq. 1 • If an off-ramp is involved calculate LEQ • if LEQ < Lup and/or Ldown then use Eq. 1 Michael Dixon

  7. Steps for Evaluating a Merge Area • Calculate the adjusted volumes (VR, VF, VD) • Step 1: Evaluate the equilibrium distance • Step 2: Calculate PFM • Step 3: Calculate V12 • Step 4: Calculate total flow entering merge area (VR12) Michael Dixon

  8. Steps for Evaluating a Merge Area (cont.) • Step 5: Capacity for downstream freeway segment (c1) • Step 6: Capacity for merge influence area (only if v/c for step 5 is less than 1)(Exhibit 25-7) • Step 7: Determine the LOS of the influence area (only if v/c for step 5 is less than 1) Michael Dixon

  9. Michael Dixon

  10. Six-Lane Example: Conditions Michael Dixon

  11. Six-Lane Example: Step 1 Michael Dixon

  12. Six-Lane Example: Step 2 and 3 Michael Dixon

  13. Six-Lane Example: Step 4 and 5 Michael Dixon

  14. Six-Lane Example: Step 6 and 7 Michael Dixon

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