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Traffic Barrier Guidelines Barrier Warrant Analysis Hands-On Workshop III July 2013

Traffic Barrier Guidelines Barrier Warrant Analysis Hands-On Workshop III July 2013. 1. References. AASHTO Roadside Design Guide, 4 th Edition-2011 Clear Zone, Chapter 3 Location of Barriers, Chapter 5 Barrier Length & End Treatment, Chapter 5 Benefit/Cost Analysis. 2.

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Traffic Barrier Guidelines Barrier Warrant Analysis Hands-On Workshop III July 2013

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  1. Traffic Barrier Guidelines Barrier Warrant AnalysisHands-On Workshop III July 2013 1

  2. References AASHTO Roadside Design Guide, 4th Edition-2011 • Clear Zone, Chapter 3 • Location of Barriers, Chapter 5 • Barrier Length & End Treatment, Chapter 5 • Benefit/Cost Analysis 2

  3. Traffic Barrier Guidelines • BWA Process • Usage Guide How Many People Brought a Copy? 3

  4. Barrier Warrant Analysis Procedure Traffic Barrier Guidelines Section 4.0 4

  5. Barrier Warrant Analysis Procedure • Identify Potential Obstacles • Name Obstacles • Prepare/Present Exhibit (Concept Meeting) 5

  6. Barrier Warrant Analysis Procedure • Identify Potential Obstacles. • Name Obstacles. • Prepare/Present Exhibit. • Each AOC shall be analyzed separately. • Establish EOTW 6

  7. a. Establish Edge of Traveled Way EOP 1’ outside of the EOTW EOTW = EOP 7

  8. Barrier Warrant Analysis Procedure • Identify Potential Obstacles. • Name Obstacles. • Prepare/Present Exhibit. • Each AOC shall be analyzed separately. • Establish EOTW • Design Speed (Speed Profile for ramps, etc.) 8

  9. Barrier Warrant Analysis Procedure • Identify Potential Obstacles. • Name Obstacles. • Prepare/Present Exhibit. • Each AOC shall be analyzed separately. • Establish EOTW • Design Speed • Design ADT 9

  10. Barrier Warrant Analysis Procedure • Identify Potential Obstacles. • Name Obstacles. • Prepare/Present Exhibit. • Each AOC shall be analyzed separately. • Establish EOTW • Design Speed • Design ADT • Length of Runout 10

  11. c. Length of Runout LR L2 Figure 5-39. Approach Barrier Layout Variables 11

  12. c. Length of Runout 12

  13. Barrier Warrant Analysis Procedure • Identify Potential Obstacles. • Name Obstacles. • Prepare/Present Exhibit. • Each AOC shall be analyzed separately. • Establish EOTW • Design Speed • Design ADT • Length of Runout • Shy Line Offset 13

  14. d. Shy Line Offset 14

  15. BarrierWarrant Analysis Procedure • Identify Potential Obstacles. • Name Obstacles. • Prepare/Present Exhibit. • Each AOC shall be analyzed separately. • Establish EOTW • Design Speed • Design ADT • Length of Runout • Shy Line Offset • Foreslope/Backslope 15

  16. f. Foreslope/Backslope Foreslopes Within clear zone 1:6 (desirable) 1:4 (maximum) Elsewhere 1:4 (desirable) 1:3 (maximum) Backslopes 1:4 (desirable) 1:2.5 (maximum) Foreslope Backslope 16

  17. Barrier Warrant Analysis Procedure (cont.) • Clear Zone 17

  18. Clear Zone: The unobstructed, traversable area provided beyond the edge of through traveled way for the recovery of errant vehicles. 18

  19. Clear Zone Distances (Feet) From Edge of Traveled Way (RDGTable 3-1) Use highest value in range 19

  20. Clear Zone Distances (Feet) From Edge of Traveled Way (Table 3-1) Use highest value in range 20

  21. Barrier Warrant Analysis Procedure (cont.) • Clear Zone • Clear Zone Adjustment 21

  22. h. Clear Zone Adjustment 22

  23. Barrier Warrant Analysis Procedure (cont.) • Clear Zone • Clear Zone Adjustment • Lateral Extent of the Area of Concern (LA) 23

  24. i. Lateral Extent of the Area of Concern LA L3 L2 Figure 5-39. Approach Barrier Layout Variables 24

  25. Barrier Warrant Analysis Procedure (cont.) • Clear Zone • Clear Zone Adjustment • Lateral Extent of the Area of Concern • Warrant Analysis Level 25

  26. j. Warrant Analysis Level • Decide Warrant Analysis Level • Level 1 • Level 2 • Level 3 • Level 0 Use Flowchart For Existing Obstacles or Flowchart for Proposed Obstacles 26

  27. Flowchart for Analysis of Existing Obstacles (Figure 5.5a) 27

  28. Flowchart for Analysis of Proposed Obstacles (Figure 5.5b) 28

  29. Warrant Analysis Level (Article 5.5) 29

  30. Level 1 Analysis (Article 5.5.1) • Level 1 – Existing AOC’s that are traversable elements or can easily be made traversable elements such as: • Existing ground mounted signs, and existing drainage items • Existing ground mounted light poles and electrical handholes 30

  31. Traversable Element (Steel or Wood) 4 in. 5 ft. RDG-Figure 4-1. Breakaway Support Stub Height Measurements 31

  32. Traversable Element 1:6 (V:H) 4’ 32

  33. Level 1 Analysis (Article 5.5.1) • Level 1 – Proposed AOC’s that are traversable elements: • Proposed Ground-Mounted Signs • Proposed Light Poles • Proposed Drainage Items (culvert and pipe ends 84” or less in vertical opening) 33

  34. Level 1 Analysis-Sample Table 34

  35. Breakaway Sign Posts An important feature of this breakaway sign system is the ability of its post support to swing up and out of the way when it is struck by an errant vehicle. 35

  36. Direction of Traffic Safety End Treatment-Steel Grate Headwall and storm sewer outlets shall be provided with appropriate safety end treatment per Standard Drawings – Section B. 36

  37. Roadway Lighting Steel Helix Foundation Needs to be a Traversable Element 37

  38. Level 2 Analysis (Article 5.5.2) When shielding is required and barrier length of need must be determined. Cantilever sign post 38

  39. Shielding- Definition • Shielding—The introduction of a barrier or crash cushion between the vehicle and an obstacle or area of concern to reduce the severity of impacts of errant vehicles. 39

  40. Level 2 Analysis Median Emergency Turnaround 40

  41. Level 2 Analysis (Article 5.5.2) This analysis is performed for:  • EXISTING/PROPOSED OBSTACLES when there are no feasible alternatives for eliminating, or reducing the impact severity of the obstacle. • PROPOSED OBSTACLES for an Alternative in a Level 3 Analysis. The length of barrier and type of terminals has to be determined for each Alternative that involves shielding of the obstacle. 41

  42. Level 3 Analysis (Article 5.5.3) The evaluation of two or more feasible alternatives for; • Removing • Relocating • Reducing the impact severity of • Shielding the obstacle This is part of the design process 42

  43. Level 3 AnalysisDetermination of Alternatives (Article 5.6.1) • If a Level 3 analysis is warranted, then the designer needs to use engineering judgment when selecting the alternatives to evaluate. • Only consider alternatives that are feasible. • Cannot analyze an alternative that leaves an obstacle unshielded in the clear zone. 43

  44. Level 3 Analysis (Article 5.6.1) • When considering relocation of a fixed object, in addition to changing the offset from the EOTW, the designer should consider relocation upstream or downstream. • Alternatives for sign truss span lengths or cantilever arm lengths shall not exceed the maximums shown on the Tollway Standard Drawings. 44

  45. Additional guidance for determination of alternatives for Level 3 Analysis • The following values shall be exceeded when relocating an obstacle onto a non-recoverable, thus undefined clear zone, foreslope or when considering leaving an obstacle unshielded on a non-recoverable foreslope: 45

  46. Roadside Safety Analysis Program (RSAP) 46

  47. Roadside Safety Analysis Program (RSAP) http://www.trb.org/Main/Blurbs/152743.aspx 47

  48. Level 3 Analysis Overhead sign to span beyond clear zone with no barrier Overhead sign to span roadway with barrier This is most common Level 3 obstacle 48

  49. Level 0 Table Requirements(Articles 5.5 and 6.13.8) • Potential AOCs not analyzed with a Level 1, 2, or 3 Analysis shall be included in a Level 0 Table. • This table should include all potential AOCs that were initially identified in the process, but were determined to be well outside of the clear zone or existing obstacles physically removed from the project and, therefore required no analysis. 49

  50. Barrier Warrant Analysis Procedure (cont.) • Clear Zone • Clear Zone Adjustment • Lateral Extent of the Area of Concern • Warrant Analysis Level • Lateral Offset of Barrier (L2) 50

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