Higway capacity manual

Highway Capacity Manual 2000 CHAPTER 25

RAMPS AND RAMP JUNCTIONS
CONTENTS
INTRODUCTION ..................................................................................................... 25-1 Scope of the Methodology ............................................................................... 25-1 Limitations of the Methodology......................................................................... 25-1 II. METHODOLOGY .................................................................................................... 25-1 Ramp Roadways .............................................................................................. 25-3 LOS .................................................................................................................. 25-4 MergeInfluence Areas ..................................................................................... 25-5 Predicting Flow Entering Lanes 1 and 2 (v12) ........................................... 25-5 Determining Capacity ................................................................................ 25-7 Determining LOS....................................................................................... 25-8 Special Cases ........................................................................................... 25-8 Two-Lane On-Ramps ......................................................................... 25-8 Lane Additions ................................................................................... 25-9 Major MergeAreas............................................................................. 25-9 On-Ramps on Ten-Lane Freeway (Five Lanes in Each Direction) ........................................................................... 25-10 Left-Hand On-Ramps ....................................................................... 25-11 Effects of Ramp Control at On-Ramps ............................................ 25-11 Diverge Influence Areas................................................................................. 25-11 Predicting Flow Entering Lanes 1 and 2 (v12) ......................................... 25-12 Determining Capacity .............................................................................. 25-14 Determining LOS ..................................................................................... 25-14 SpecialCases ......................................................................................... 25-15 Two-Lane Off-Ramps ....................................................................... 25-15 Lane Drops ...................................................................................... 25-16 Major Diverge Areas ........................................................................25-16 Off-Ramps on Ten-Lane Freeways (Five Lanes in One Direction) ............................................................................. 25-17 Left-Hand Off-Ramps ....................................................................... 25-17 Overlapping Ramp Influence Areas ............................................................... 25-17 Determining Speed at Ramp Influence Areas................................................ 25-18 III. APPLICATIONS .................................................................................................... 25-19 Computational Steps ...................................................................................... 25-20 Planning Applications..................................................................................... 25-20 Analysis Tools ................................................................................................ 25-22 IV. EXAMPLE PROBLEMS ......................................................................................... 25-23 Example Problem 1 ........................................................................................ 25-24 Example Problem 2 (Part I)...