At-Grade Intersection

1. At-Grade Intersection

2. Types of Intersection Maneuvers Source: FHWA Roundabout Guide

3. 4-way Intersection 32 conflict points  High speed impacts  High angle impacts

4. Roundabout 8 conflict points 75% reduction in Motor Vehicle conflicts  Low speed impacts  Low angle impacts

5. AFTER BEFORE

11. Intersection Control Hierarchy • No Control (Basic Rule) • Yield Sign • Stop Sign – normal control method • All-Way Stop • Roundabout • Traffic Signal • Grade Separation

12. Traffic Signals Advantages • Orderly movement of traffic • Reduces certain types of crashes • Interrupts heavy flows for minor movements • Promotes driver confidence • Provides gap for minor movements

13. Traffic Signals Disadvantages • Increases total delay, especially off-peak • Increases fuel consumption • Increases crashes • Induces road users to less appropriate routes • Unnecessary delay if not properly located • Bad timing, bad engineer!

14. GRADE SEPARATION • High flows • Minimal delays • Expensive

15. At-Grade Railway Crossings Horizontal alignment • Intersection at right angle on a tangent section • No other nearby intersections Vertical alignment • Intersection as level as possible • Adequate view of crossing • Vertical profile should prevent vehicles with low clearance from being caught on the track (see below)

22. Traffic Lane

23. Auxiliary Lanes

24. Auxiliary Lanes Auxiliary lanes: • remove accelerating or decelerating vehicles from the through lanes • store turning vehicles • increase road capacity Types of acceleration or deceleration lanes parallel lanes directional lanes (tapers)

25. Auxiliary LanesTapers MEDIAN MEDIAN

26. Lane Shift

32. Offset Left-Turn Lanes

33. Offset Left-Turn Lanes

34. Continuous Left-Turn Lanes

35. Minimum Design for U-TurnsExhibit 9-92

38. Objectives of Channelization and Design Elements to Achieve Them

46. Design of Channelization q

47. Design of Channelization

48. Design of Channelization

49. Design of Channelization

50. Design of Channelization