CE 578 Highway Traffic Operations

1
CE 578 Highway Traffic Operations

• Freeways Ramps and Ramp Junctions Examples and
  Special Applications for Merge Areas

2
Objectives

• Analysis for six-lane freeways
• Analysis for eight-lane freeways
• Analysis of special cases

3
Special Cases

• Ten-lane freeways
• Two-lane on-ramp
• Major merge areas
• Lane additions
• Left-hand on-ramp

4
Special Cases Ten-Lane Freeways

• Same as eight lane analysis
• Use Exhibit 25-11
• Use Equation 25-7
• Use vF4eff in Eight-lane equation for PFM

5
Special Cases Two-Lane On-Ramp
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Special Cases Two-Lane On-Ramp

• Densities
• Relative operations
• Two changes to basic methodology
• Calculation of PFM
• Length of acceleration lane for calculation of
  density
• Capacity values are unaffected for vFO and vR12.

7
Special Cases Major Merge Areas
8
Special Cases Major Merge Areas

• Each entering roadways is at or near freeway
  design standards
• No acceleration lanes involved
• Analyze as if the two entering and the one
  exiting legs are basic freeway sections, using
  Exhibit 25-7

9
Special Cases Lane Additions

• One lane addition
• ramp roadway capacity governs
• analyze downstream leg as basic freeway section
• Two lane addition analyze as major merge area
• Lane dropped within 2500 ft analyze as weaving
  area

10
Special Cases Left-Hand On-Ramp

• Influence area same length ? left two lanes
• Calculate PFM for left two lanes
• Capacity
• Density
• Speed