1. 3/6/06Michael Dixon1 CE 578 Highway Traffic Operations Lecture 21: Freeway Ramps and Ramp Junctions Diverge Areas

2. 3/6/06Michael Dixon2 Objectives Basic concepts Important variables Relate to merge areas

3. 3/6/06Michael Dixon3 Basic Concepts Volume v 12 Capacities –Total departing –Prior to deceleration lane –Downstream legs Determine influence area flow density

4. 3/6/06Michael Dixon4 Important Variables L D V R V D V U V 12 V F V FO

5. 3/6/06Michael Dixon5 Important Variables (cont.)

6. 3/6/06Michael Dixon6 Important Variables (cont.)

7. 3/6/06Michael Dixon7 Relation to Merge Area Procedure Estimate V 12 using V 12 = V R + (V F – V R )*P FD

8. 3/6/06Michael Dixon8 Ramp Sequence Scenarios

9. 3/6/06Michael Dixon9 Ramp Sequence Scenarios (cont.) Ramps with no affect--- Upstream on-ramp: Downstream off-ramp: Both Upstream on-ramp and Downstream off- ramp: Use for L EQ of upstream on-ramp Use for L EQ of downstream off-ramp

10. 3/6/06Michael Dixon10 Capacity Comparisons

11. 3/6/06Michael Dixon11 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 (______________)

12. 3/6/06Michael Dixon12

13. 3/6/06Michael Dixon13 Determining LOS Calculate diverge area density: D R = 4.252 + 0.0086v 12 – 0.009L D Use same LOS table