Special Topics: Overlaps By Michael P. Dixon, Ph.D.

1. Special Topics: OverlapsByMichael P. Dixon, Ph.D.

2. Objectives • Learn how overlaps are calculated • Learn why they can be beneficial • Learn how they are applied

3. Steps to Developing Overlaps • Step 1: Determine values for each lane group • Step 2: Determine location of overlaps • Step 3: Sum the values for the critical lane groups • Step 4: Calculate cycle length • Step 5: Distribute green time

4. A1 A2 A3 B C R1 263 R2 386 37 246 232 Ring Diagram: Four Phase with Overlaps 453 281 158 Step 1: Determine Lane Group Values • Values can be in the form of: • V/s ratios, or • Adjusted volumes

5. A1 A2 A3 B C R1 R2 Ring Diagram: Four Phase with Overlaps Step 2: Determine location of overlaps Target phases with unbalanced flows 263 386 37 246 232 453 281 158

6. A1 A2 A3 B C R1 263 R2 386 37 246 232 Ring Diagram: Four Phase with Overlaps 453 281 158 Step 3: Sum the Values for the Critical Lane Groups • Follow the critical path 1155 vph

7. Step 4: Calculate Cycle Length • C = (N*L*(v/c)des) / [1 - (v/s)ic] or, • C = (N*L) / [1 - Vc/ (3600/h*(v/c)des*PHF)] • For our case C = 70 sec • Vc = 1155 vehicle/hour • h = 2.2 seconds/vehicle • PHF = 1.0 • (v/c)des = 0.85 • N = 4 phases • tL = 3 seconds/phase

8. Step 4: Calculate Cycle Length (cont.) • What would the cycle length be if their were no overlaps? A1 A2 A3 B C R1 263 386 37 246 R2 1155 vph 232 453 281 158 Ring Diagram: Four Phase with Overlaps

9. A1 A2 A3 B C R1 R2 Ring Diagram: Four Phase with Overlaps Blue = w/o overlaps; Red = w/ overlaps Step 4: Calculate Cycle Length (cont.) • What would the cycle length be if the EB and WB through values were switched (with and without overlaps)? 263 37 453 246 1088 vph 232 386 281 1155 vph 158

10. A1 A2 A3 B C R1 263 R2 386 37 246 232 Ring Diagram: Four Phase with Overlaps 453 281 158 Step 5: Distribute Green Time • Step 5.a: Determine green times of phases that have no overlaps • Step 5.b: Determine green times of phases on side(s) of barrier with overlaps

11. Step 5.b: Definition • Values are categorized by the phases whose green times they define

12. Step 5.b: Determine green times of phases on side(s) of barrier with overlaps • Calculate gA1: If phase A1 is defined by a lane group in the critical ring then • Otherwise

13. A1 A2 A3 B C R1 263 R2 386 37 246 232 Ring Diagram: Four Phase with Overlaps 453 281 158 What are the volumes of interest? VA1 = 37 vph VA3 = 453 vph VA2+A3 = 386 vph VA1+A2 = 158 vph Vc = 1155 vph Is phase A1 defined by a lane group that is in the critical ring? How much effective green time for A1?

14. Step 5.b: Determine green times of phases on side(s) of barrier with overlaps (cont.) • Calculate gA3: If phase A3 is defined by a lane group in the critical ring then • Otherwise

15. A1 A2 A3 B C R1 263 R2 386 37 246 232 Ring Diagram: Four Phase with Overlaps 453 281 158 What are the volumes of interest? VA1 = 37 vph VA3 = 453 vph VA2+A3 = 386 vph VA1+A2 = 158 vph Vc = 1155 vph Is phase A3 defined by a lane group that is in the critical ring? How much effective green time for A3?

16. Step 5.b: Determine green times of phases on side(s) of barrier with overlaps (cont.) • Calculate gA2: If phase A1 + A2 is defined by a lane group in the critical ring then • Where • Otherwise • Where

17. A1 A2 A3 B C R1 263 R2 386 37 246 232 Ring Diagram: Four Phase with Overlaps 453 281 158 What are the volumes of interest? VA1 = 37 vph VA3 = 453 vph VA2+A3 = 386 vph VA1+A2 = 158 vph Vc = 1155 vph How much effective green time for A2?