roadside safety guardrail design - in.govdesirable place gr at 12’ from ep use nested gr if low...
TRANSCRIPT
1
ROADSIDE SAFETY &
GUARDRAIL DESIGN
2
PRESENTATION
ROADSIDE SAFETYClear Zone & Obstruction Free ZoneTreatment of Obstructions Construction CZ
GUARDRAIL DESIGNGR PlacementGR Design for 3R ProjectsGR at Large Structures
Design Exceptions Common Mistakes & OmissionsPractice Pointers
3
Clear Zone Concept
Space for Vehicles Run-off-the-Road to Gain ControlAmount of Obstruction-Free Area for Vehicle RecoveryLike “Airport Runway” - Free of ObstructionsPlace Roadside Hazards Away from Pavement
4
Clear Zone Applicability
New Construction & Reconstruction3R/Partial 4R on InterstatesDesirable for 3RCost Effectiveness of Corrective MeasuresClear Zone values are not absoluteCZ Outside R/W – Use R/WEngineering Judgment Provide Consistent CZLevel 2 Design Exception
5Figure 49-2A
Clear Zone Distances
Total ADT on 2-Lane RdwysDirectional ADT on Divided Highways.Compare CZ for Aux. Lane vs MainlineShow CZ on Typicals
6Figure 49-2C
Horizontal Curve Adjustments
CZ = K * CZtc cz
K = Fig. 49-2BCZ
7
Obstruction Free Zone Concept
3R ProjectsAmount of Obstruction-Free Area next to RdwyNot the same as CZ Provide CZ, if practicalOFZ Width Varies
Des Speed, Arterial/ Collector, ADT Provide Traversable DitchesLevel 2 Design Exception
8
Typical Obstructions
TreesRevetment Riprap Ditches Non-Traversable Culvert EndsNon-Traversable DitchesConcrete HeadwallsUtility poles Bodies of water, permanent water depth>2’
Non traversable castings
9
1) Remove or Redesign2) Relocate Outside of CZ3) Make Breakaway to Reduce Impact Severity4) Shield with Traffic Barrier5) Delineate if other Treatments not Practical
Treatment of Obstructions
10
Construction Roadside Safety
IDM 82-4.0 Traffic Control Roadside Safety Reduce Motorist’s Exposure to Potential HazardsMaximize SeparationMinimize Positive Protection Devices
Applies to all Project TypesAnalysis & Review required for each MOT Phase
Construction CZFig. 82-4B
11
Construction Roadside Safety
Temporary Traffic BarrierFlare Ends Outside of Const. CZAvoid Openings in BarriersAvoid using in Tapers. Provide Shy Line OffsetCheck Horizontal SSD thru Tapers/Transitions
Plan DetailsShow CZ on Typical MOT SectionsShow CZ Design SpeedAllowable Flare & Taper RatesSummarize Quantities for each Phase
Pavement Drop-offsPrefer to Close Lane3” Max Drop-off at End of DayTemp Wedge at 1:1 next to Lane
12
GR Lateral PlacementPlace as Far Away from EP as PossibleShy Line Offset - Fig 49-5F Evaluate Alternatives
Additional CostReduced Barrier length, MaintenanceAccident History
INDOT Std Revisions Under Review8’ posts Backfill Material - Cohesive soils not CAB
Pave Shldr to Face of GR if offset 2’ or lessIf GR offset > 2’, Addt’l 2’ Paved not req’d
Varies
13
GR at Curb Locations
Avoid using GR behind curbs Best to use Mountable CurbOffset GR to Shy Line OffsetGR at Face of Curb
Shy Line Offset
E.P
.
14
Barrier Deflection
Clearance Face of GR to Fixed ObjectBased on Dynamic Deflection of Barrier/GR INDOT Std Revisions 8’ posts & BackfillCheck for Fixed Objects and Drop-offs
15
GR Need Horizontal Curves
GRAPHICAL SOLUTION REQUIREDINVESTIGATE BOTH ALTERNATIVESUSE SHORTEST LENGTH OF NEED
16
GR Alternate Offset
Tapered GR Example
17
Non-Recoverable Slopes
Non-Recoverable Fill Slope
No Obstructions in Non-Recoverable Slope
Point of Hazard*
18
GR Design Non-Recoverable Slopes
Traversable Ditch Cross Section Preferred
Example GR Design with 3:1 Slopes
19
GR Design Non Recoverable Slopes
Example GR Design with 3:1 Slopes
20
GR at Large Structures
New Construction 70 MPH Des SpeedNew Alignment – Divided HwyPerpetuate CZ thru Structure
21
Drainage Structures
1’ to 5’ Cross PipesUse Safety Metal ESSkew > 10 Deg Use GBES
5.5’ and Larger – End Inside CZIf Cost Effective, provide Traversable ESDesirable Place GR at 12’ from EPUse Nested GR if Low Fill
5.5’ and Larger – End Outside CZDesirable Place GR on slope away from EP Desirable Place GR at 12’ from EP
Ditch InletsE-7 and F-7 Not Within CZ Use Pipe Catch BasinOther Type with less than 4” Protrusion
0
0
0
22
Level 2 DECZ and OFZProvide Brief RationaleAlternates Considered
Document to FileSubmit to Project ManagerDiscuss at Field Check Local Projects need LPA Sign-off
Design Exceptions
23
Incorrect CZ DistanceIncorrect CZ AdjustmentCZ Not Shown on Typical SectionsObstructions within OFZ or CZObstructions not Shielded or TraversableNon-Traversable DitchesDesign Exceptions Not Documented Using less than 100’ of Nested GR
Common Mistakes & Omissions
24
Perform CZ reviewPlot CZ/OFZ on Plans Provide Consistent CZDetermine if any obstructions within CZDetermine/Verify Corrective ActionDiscuss CZ/OFZ at Field ChecksDocument DeficienciesCheck MOT Plan and CZ
Practice Pointers
25
ROADSIDE SAFETY &
GUARDRAIL DESIGN