Traffic Barrier Guidelines Other Considerations Workshop V September-October 2015.

Traffic Barrier Guidelines Other Considerations

Workshop VSeptember-October 2015

Starts at the Site Visit

AOC 1

Identify AOC’s1. Bridge Pier2. Bridge Cone3. Light Pole4. Control Cabinet5. Sign Electric Panel6. Sign Foundation7. Sign Panel8. Trees

AOC 2

AOC 3

AOC 4

AOC 5

AOC 6

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How to address the area overall?

AOC 7

AOC 8

AOC’s in Close Proximity

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AOC in Close ProximityExample #1GAP < 100’

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14+25

Culvert - AOC #1

14+03.12 17+22

OH Sign- AOC #2

15+70

16+12.517+08.12

Upstream Terminal End

19+05

19+17.5

Downstream Terminal End

Upstream Terminal End Downstream

Terminal End

95.62’

Gap

Total Length of Need = 480’

EOTW


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PON PON

16+00 18+95

AOC in Close ProximityExample #2GAP > 100’

6

14+25

Culvert - AOC #1

14+03.12 17+72

OH Sign- AOC #2

15+70

16+12.517+58.12


19+55

19+67.5




145.62’

Gap

EOTW


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PON PON

16+00 19+45

Length of Need

Length of Need

AOC in Close ProximityExample #3

Overlap

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14+25

Culvert - AOC #1

14+03.12 16+22

OH Sign- AOC #2

15+70

16+12.5

16+08.12Upstream Terminal End

18+05

18+17.5

Downstream Terminal End Downstream

Terminal End

4.38’ Overlap


Total Length of Need=380’

EOTW


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PON PON

16+00 17+95

AOC in Close ProximityFormat

Examples

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Example- AOC Summary Table FormatLEGENDPOINT OF NEED STATIONDOWNSTREAM END OF GUARDRAIL STATION

AOC SUMMARY TABLEAOC 1 15+00 26+00AOC 2 15+00 22+50AOC 3 16+25 27+00AOC 4 19+00 23+00 SUMMARY 15+00 27+00TOTAL LON 15+00 to 27+00 = 1,200 FT

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AOC- Color Coded System

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Color Coded AOC’s (Level Analysis)

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Considerations for Adjusting Guardrail

Lengths

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Considerations for Adjusting GR lengths TBT T2-Condition 3

Would not be used when: Guardrail length < Minimum length

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Considerations for Adjusting GR lengths Positioning of minimum guardrail length

Move upstream or downstream to avoid gap < 100’ (or) overlap with adjacent AOC.

Obstacle in TBT T1/T1-A recovery area Positioning of guardrail installation move

upstream or downstream need to meet barrier limit calculation.

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Combining Areas of Concern Case 1

When the two AOC’s are generally at the same station, but with different offsets.

AOC 1 AOC 2

AOC further from the roadway will result in the longer length of need.

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Combining Areas of Concern Case 2

When a fixed object is located in the midst of a long slope AOC.

V

H

1: 2.5 (V:H)

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The slope AOC will control the length of need.

Design Considerations

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Barrier Installation Conflicts

Retaining Wall Conflict• Last six posts for Traffic Barrier Terminal Type T6 were omitted.

Retaining wall design and location could have eliminated the conflicts.

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Barrier Installation Conflicts

Drainage Structure Conflict:Last two posts for Traffic Barrier Terminal Type T6 were omitted.

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Traversable Element

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Ground-Mounted Sign Supports (Article 3.4.1)

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Foreslope 1:6 (V:H) or Flatter

Traversable Element

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Barrier Clearance Distance

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Barrier Terminal Connection

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Drainage Structure Conflict

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Parapet or Concrete Barrier Contributes Toward the LON.

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AOC #1-Bridge Parapet Blunt End

AOC #2-Waterway

AOC #1-LONAOC #2-LONBridge parapet contributes towards the shielding for AOC #2

Guardrail=LON-Terminal Contribution-Parapet Contribution

Runoff Path

Area of Concern

MVDS

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Runoff Path

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AOC #1

AOC #2

Runoff Path

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AOC #1

AOC #2

LR

x

Y

Runoff Path

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AOC #1

AOC #2

LR

Speed Profile-Ramp EntranceService Interchange

30 mph

20 mph

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----------------------------------------------------------------------------

35 mph

40 mph

160’270’

Acceleration Lengths

610’

50 mph

Deceleration Length needed

315’

Length ~ 850’

Acceleration to 50 mph does not provide the required deceleration distance to reduce to 30 mph.

Speed Profile-Ramp EntranceService Interchange

30 mph

20 mph

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----------------------------------------------------------------------------

35 mph

40 mph

160’270’

Acceleration Lengths

40 mph

Deceleration Length needed

185’

Length ~ 850’

Acceleration to 40 mph and holding for 395’ provides the required deceleration distance to reduce speed to 30 mph.

395’

Speed Profile-Mainline Exit

• Directional-50 mph minimum (applies to sharpest curve) Ramp with a design speed of 50 mph or greater on which vehicles do not stop.

Service Interchange

50 mph

60 mph

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Hot List-Common Mistakes1. Lack of DSE Quality Control/Quality Assurance

Designers need to thoroughly check their work before submitting, and follow their own CQP. A common problem is when redundant information is not transferred properly between calculation sheets and plan view exhibits.

Reference DSE Manual Section 7.0.

2. Identification of All Potential Obstacles In many cases not all potential obstacles have been included in the BWA report.

Additionally, in many cases there are obstacles identified on the location plans but not analyzed in the report. All obstacles are to be addressed as level 1, 2, 3 analyses or included in the Level 0 Table.

Reference TBG Article 4.0.

3. Site Plan Information Missing The site plan shall show the recovery area at Type T1 and T1-A terminals, label all

nearby obstacles, gutters, Y at PON station only. Also the text size used should meet or exceed the minimum height (0.11”).


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Hot List-Common Mistakes4. Drainage Structures Placed Within the Limits of Traffic Barrier Terminals

This issue often results in post spacing that is not in accordance with the Tollway Standards and modification to the Tollway Standards for terminals is not allowed.


5. Including Items in Level 1 and Level 0 Tables That Are Not Appropriate Level Items Per the TBG only items that are or can be made Traversable Elements should be included in

the Level 1 table. Potential AOC’s not analyzed with a Level 1, 2, or 3 Analysis, shall be included in a Level 0 Table. Obstacles that are shielded by barrier for other AOC’s are Level 2 items, and are noted in the other AOC’s analysis.


6. Not Addressing Barrier Clearance Distance Designers need to consider the offset from the back of guardrail to light poles, sign

foundations, walls, and other obstacles and note these distances on the site plans. Minimum barrier clearance distances are also provided on Tollway Standard C1, sheet 4 of 4.


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Hot List-Common Mistakes7. Intermixing Traffic Barrier Terminal (TBT) Type T6 and TBT Type T6B

The T6 terminal is used with gutter and the T6B is used when no gutter is present. Reference TBG Articles 10.6.1 and 10.6.2.

8. Compact Disc (CD) submittal of RSAP files When applicable, include a CD containing the RSAP (.rpd) file(s) used in the Level 3 analysis

with the hard copy of submitted barrier warrant. Reference TBG Article 6.13.

9. Not giving guidance for revised sheets placement When submitting revised sheets only, include a document with step-by-step guidance for

inserting revised and/or new sheets, and removing sheets from the barrier warrant. Submitting just a revised Table of Contents is not sufficient.

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Hot List-Common Mistakes10. Not Investigating Feasible Alternatives

When evaluating potential obstacles, designers need to select alternatives that are feasible. For example, in many instances the designer has evaluated an alternative to leave an obstacle unshielded in the clear zone; this is not a feasible alternative as it violates Tollway Policy. A Level 3 Analysis requires the evaluation of two or more feasible alternatives for eliminating or reducing the severity of the obstacle.


11. No Level 3 Analysis When a Level 3 analysis is not performed for an obstacle that would usually warrant such

an analysis, the reason for this should be given in the AOC’s analysis. Reference TBG Section 5.5.3.

12. Not Evaluating Obstacles From Both Mainline And Secondary Road Perspective When the potential obstacle is along a ramp, C-D road, or auxiliary lane near the mainline

or within the gore area, the potential obstacle needs to be evaluated from both mainline and ramp perspective. Utilize respective edge of traveled way (EOTW), speed, and volumes for each perspective and determine the controlling situation.

Reference TBG Section 4.0.

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Hot List-Common Mistakes13. Analysis Of Closely Spaced Or Overlapping Potential Obstacles

When multiple potential obstacles are in the same area they need to be analyzed independently. A summary is to be included showing the controlling upstream and downstream obstacles and the rounded length of guardrail per the overall length of need. In cases where multiple obstacles exist in the midst of a long slope obstacle, they do not need to be analyzed independently, but notes need to be included in the BWA indicating this, and the obstacles must be labeled on the slope obstacle site plan (Refer to TBG Section 4.0 step 5).

Reference TBG Section 4.0.5.

14. Speed Profiles Not Done Correctly Speed profiles are required for ramp analyses to show the acceleration and/or deceleration

per AASHTO and the resultant design speed at the potential obstacle. Design speeds of curves shall be shown. The format shown in the TBG Art. 6.14.1 should be followed.


15. Slope Obstacles Not Analyzed Correctly “Critical Slopes” are defined as foreslopes steeper than 1:3 (V:H), and do not always require shielding.

The upstream and downstream limits of a slope obstacle are determined by RDG Figure 5-1b. Interpolate between cross sections to determine the limits.

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Questions?

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Traffic Barrier Guidelines Other Considerations Workshop V September-October 2015.

Documents

Transcript of Traffic Barrier Guidelines Other Considerations Workshop V September-October 2015.