Module 1 Introduction Intersection & Interchange Geometrics (IIG) Innovative Design Considerations for All Users

COURSE INSTRUCTORS 2 Mark Doctor Atlanta, GA (404) George Merritt Atlanta, GA (404) FHWA Office of Technical Services Resource Center Safety & Design Team

SELF INTRODUCTIONS  Your Name, Organization & Position  What you would like to learn from this workshop 3

LOGISTICS  Please silence cell phones  Please ask questions  Breaks / Lunch  Sign-in sheet & Registration Form  Post-test 4

LEARNING OUTCOMES Module 1 - Introduction  Define what is meant by “innovative” or “alternative” intersections and interchanges  Describe their potential advantages  Define “intersection conflict points” and apply the concept to assess potential safety differences among intersections 5

Module 1 Introduction WHY DO WE NEED INNOVATIVE INTERSECTION & INTERCHANGE DESIGNS?

WHY ALTERNATIVE INTERSECTIONS & INTERCHANGES? Visualize a high volume intersection or interchange you have travelled through recently What do you see? Who do you see? Insert mental image of your intersection here ??? 7

Increasing Congestion Too Many Crashes Quantity and severity Safety for ALL users Not Enough Funding Time Consuming Projects Inability for more right-of-way Minimize the impacts of projects Environmental, social, economic Source: Mark Doctor, FHWA WHAT ARE THE PROBLEMS? 8

Photo Source: Mark Doctor, FHWA WHY INNOVATIVE INTERSECTIONS & INTERCHANGES? Intersections are usually the bottlenecks along high volume roadways and are often a safety concern 9

Angle crashes account for over 40% of fatal crashes at intersections INTERSECTION SAFETY FACTS 10

Left turn crashes account for over 20% of fatal crashes at intersections INTERSECTION SAFETY FACTS 11

INTERSECTION SAFETY FACTS Ped/Bike crashes account for 25% of fatal crashes at signalized intersections 12

Source: North Carolina DOT 16 Crossing Conflicts INTERSECTION CONFLICT POINTS - VEHICLES

16 Crossing Conflicts

15 INTERSECTION CONFLICT POINTS – VEHICLES/PEDS Four vehicle/pedestrian conflicts per crossing Conflicts involving RTOR and “permissive” left turns can be particularly problematic

Module 1 Introduction WHAT ARE ALTERNATIVE INTERSECTIONS & INTERCHANGES?

Innovative designs that: Improve the way traffic makes certain movements by eliminating, relocating or modifying conflict points Strategically improve signalization Source: Mark Doctor, FHWA Source: Missouri Department of Transportation Source FHWA WHAT ARE ALTERNATIVE INTERSECTIONS & INTERCHANGES? 17

SIGNAL PHASING Basic two- phase signal operation Source: MnDOT Traffic Signal Timing and Coordination Manual

SIGNAL PHASING Source: MnDOT Traffic Signal Timing and Coordination Manual Adding “protected” left-turn phases is common as volumes increase

SIGNAL PHASING Adding more phases essentially “steals” time away from the major through movement and can increase intersection delays

Strategically relocating left turn movements can provide more green time to through traffic SIGNAL PHASING

Fewer phases – GOOD / Left turns - BAD Photo: 2-Phase operation at a Median U-turn Intersection IN SUMMARY …

BENEFITS OF INTERSECTION & INTERCHANGE GEOMETRICS SAFETY MOBILITY VALUE Fewer conflict points Significant Before/After Crash Reductions Less delay Reduced congestion Less ROW Less construction costs Implemented quicker

LEARNING OUTCOMES Module 1 - Introduction  Define what is meant by “innovative” or “alternative” intersections and interchanges  Describe their potential advantages  Define “intersection conflict points” and apply the concept to assess potential safety differences among intersections 24

LEARNING CHECK Module 1 - Introduction  What are “innovative” or “alternative” intersections and interchanges? 25 They are designs that: Improve the way traffic makes certain movements to eliminate, relocate or modify conflict points Strategically improve signalization

LEARNING CHECK Module 1 - Introduction  What are the potential advantages of innovative intersections & interchanges? 26 Safety Mobility Value

LEARNING CHECK Module 1 - Introduction  Define “intersection conflict points” and apply the concept to assess potential safety differences among intersections 27 At a conventional four-leg intersection, the combination of various through and turning movements create a total of 32 points of conflict. These conflict points can be classified into three different types: crossing, merging, and diverging. Crossing maneuvers occur where vehicle travel paths cross one another, merging maneuvers occur where vehicles from one traffic stream enter into another, and diverging are located at points in which vehicles depart a traffic stream.

QUESTIONS