CLEAR-ZONE / 1. Trees and shrubs 3350 OBSTRUCTION-FREE ...

1

CLEARCLEAR--ZONE /ZONE /OBSTRUCTIONOBSTRUCTION--FREEFREE--ZONEZONE

CONCEPTCONCEPT

CLEAR ZONE (CZ)CLEAR ZONE (CZ)The adequate roadside width The adequate roadside width

for 80% of errant motorists to for 80% of errant motorists to be able to regain control of be able to regain control of their vehicles their vehicles –– applicable to applicable to new or reconstruction work new or reconstruction work

areaarea

1999 1999 –– Top 5 Fixed Objects Top 5 Fixed Objects Causes of FatalitiesCauses of Fatalities

1. Trees and shrubs 33501. Trees and shrubs 33502. Culverts / ditches 14802. Culverts / ditches 14803. Embankments 12703. Embankments 12704. Guardrail 11854. Guardrail 11855. Utility poles 10705. Utility poles 1070

CLEAR ZONECLEAR ZONE

ClearClear--Zone widths for various Design Zone widths for various Design Speeds, Speeds, AADTsAADTs, Cut Slopes and Fill , Cut Slopes and Fill Slopes are shown in IDM Figure 49Slopes are shown in IDM Figure 49--2A.2A.Figure values applicable to shoulder Figure values applicable to shoulder widths up to 12 feetwidths up to 12 feetMeasured from edge of adjacent travel Measured from edge of adjacent travel lanelaneWhere inadequate R/W width Where inadequate R/W width –– R/W is R/W is CZCZ

2

CLEAR ZONECLEAR ZONE

Design Year ADTDesign Year ADT –– Total ADT on Total ADT on twotwo--way roadway or Directional way roadway or Directional ADT on oneADT on one--way roadway (ramp, way roadway (ramp, or each roadway of divided or each roadway of divided highway)highway)CZ CZ –– Constant as much as practical Constant as much as practical on a project or on adjacent on a project or on adjacent project if parallel design time project if parallel design time periodperiod

CLEARCLEAR--ZONE ADJUSTMENTSZONE ADJUSTMENTSHorizontal Curve Correction Factors Horizontal Curve Correction Factors –– See IDM See IDM Figure 49Figure 49--2B for curve radii up to 2860 feet2B for curve radii up to 2860 feetHorizontal curve / CZ adjustment transition Horizontal curve / CZ adjustment transition ––See IDM Figure 49See IDM Figure 49--2C2CApplies to each new construction / Applies to each new construction / reconstruction, 3R / partial 4R projectreconstruction, 3R / partial 4R projectIf unable to practically apply If unable to practically apply –– requires Level requires Level Two Design ExceptionTwo Design ExceptionSee IDM Figure 49See IDM Figure 49--2D for CZ tangent to 2D for CZ tangent to curve transitioncurve transition

3

CLEARCLEAR--ZONE ADJUSTMENTSZONE ADJUSTMENTS

Slope Averaging Slope Averaging –– Flat to 4:1 slopes Flat to 4:1 slopes within CZ within CZ –– See IDM Figure 49See IDM Figure 49--2E2EAveraging starts at edge of shoulderAveraging starts at edge of shoulderOnly applies to slopes in same direction Only applies to slopes in same direction –– cannot average cut and fill slopes cannot average cut and fill slopes togethertogetherFill slope steeper than 4:1 nonFill slope steeper than 4:1 non--recoverable recoverable ––Provide clear Provide clear runoutrunout area area at bottom of slope at bottom of slope –– See IDM Figure See IDM Figure 4949--2F for example2F for example

4

CLEARCLEAR--ZONE APPLICATIONSZONE APPLICATIONS

New facility New facility –– Provide 6:1 fill slope adjacent to Provide 6:1 fill slope adjacent to roadway in CZ roadway in CZ –– See IDM Figure 49See IDM Figure 49--2G2GReconstructed cut slope (traversable ditch) Reconstructed cut slope (traversable ditch) ––check both cut and fill CZ widths check both cut and fill CZ widths –– Use Use greatest greatest Toe of Toe of backslopebackslope within 10 feet of shoulder within 10 feet of shoulder edge (break) edge (break) –– Use Use backslopebackslope CZCZDitch not traversable Ditch not traversable –– ReconstructReconstruct2:1 2:1 backslopebackslope retained or provided retained or provided –– See IDM See IDM Figure 49Figure 49--2H2H

5


Cut slope (new facility) Cut slope (new facility) –– See IDM Figure See IDM Figure 4949--2G, and do not use 2:1 2G, and do not use 2:1 backslopesbackslopesAuxiliary lane Auxiliary lane –– Determine CZ for both Determine CZ for both ML and auxiliary lane, using ML design ML and auxiliary lane, using ML design speed and respective speed and respective ADTsADTs –– Use most Use most extreme CZ extreme CZ –– See IDM Figure 49See IDM Figure 49--2 I2 IRamp CZ Ramp CZ –– Determined as on ML Determined as on ML ––Design speed varies along a ramp Design speed varies along a ramp


Rural or urban collector with Rural or urban collector with design speed 30 MPH or less, or design speed 30 MPH or less, or local road or street local road or street –– CZ is 10 feet CZ is 10 feet –– Adjust for curvesAdjust for curves

Urban road or street with vertical Urban road or street with vertical curbs curbs –– CZ is 10 feet or to R/W CZ is 10 feet or to R/W line, whichever is lessline, whichever is less


Desirable transverse slopes within Desirable transverse slopes within the Clear Zone are shown in IDM the Clear Zone are shown in IDM Fig. 49Fig. 49--3A3A

6

APPURTENANCEAPPURTENANCE--FREE AREAFREE AREA

Area measured from face of curb or Area measured from face of curb or edge of travel lane, or if no curb, free edge of travel lane, or if no curb, free of anything protruding above paved or of anything protruding above paved or earth surfaceearth surface

Area is 20 inches wide except at signal Area is 20 inches wide except at signal support where it is 30 inchessupport where it is 30 inches

See IDM Figure 49See IDM Figure 49--2K2K

PARKING LANES ON STREETPARKING LANES ON STREET

Continuous (24 hr.) parking Continuous (24 hr.) parking –– No CZ No CZ required but provide appurtenancerequired but provide appurtenance--free areafree area

Sometimes used as travel lane Sometimes used as travel lane ––CZ required as measured from CZ required as measured from right edge of parking laneright edge of parking lane

7

CLEARCLEAR--ZONEZONEOBSTRUCTIONSOBSTRUCTIONS

TREATMENT OF TREATMENT OF OBSTRUCTIONSOBSTRUCTIONS

Remove and DisposeRemove and DisposeRelocate Outside CZRelocate Outside CZRelocate within CZ for Safe TraversalRelocate within CZ for Safe TraversalModify in Place for Safe TraversalModify in Place for Safe TraversalLeave in Place and Make BreakawayLeave in Place and Make BreakawayLeave in Place and Shield with BarrierLeave in Place and Shield with BarrierLeave in Place and DelineateLeave in Place and Delineate

TYPES OF OBSTRUCTIONSTYPES OF OBSTRUCTIONS

Body of Water 2 ft or deeperBody of Water 2 ft or deeperBoulderBoulderBridgeBridge--Cone Slope, 2:1 or steeperCone Slope, 2:1 or steeperBridge PierBridge PierBridgeBridge--Railing EndRailing EndCulvert End without acceptable end Culvert End without acceptable end treatment (point where culvert top treatment (point where culvert top protrudes from protrudes from sideslopesideslope is within CZ) is within CZ)


Concrete Headwall on culvert Concrete Headwall on culvert Ditch or Ditch or SideslopeSideslope Steeper than 4:1Steeper than 4:1Mailbox Support (wood post greater Mailbox Support (wood post greater than 4 x 4 square or 4.5 in. than 4 x 4 square or 4.5 in. diadia., or steel ., or steel pipe 1.5 to 2 in. pipe 1.5 to 2 in. diadia.).)NonNon--Breakaway Sign or Lighting Breakaway Sign or Lighting SupportSupportRetaining Wall EndRetaining Wall EndRough Rock CutRough Rock Cut

8


Rutted or Eroded Rutted or Eroded sideslopesideslopeSteel Pipe or Sign Post with inside Steel Pipe or Sign Post with inside diameter greater than 2 in.diameter greater than 2 in.TreeTreeUtility PoleUtility PoleWood Post, crossWood Post, cross--sectional area sectional area greater than 23 in.greater than 23 in.22


SideslopeSideslope at edge of shoulder at edge of shoulder steeper than 1:1 and higher than steeper than 1:1 and higher than 2 feet2 feetDriveway or Public Road Approach, Driveway or Public Road Approach, ditch check, or median crossover ditch check, or median crossover transverse slopes steeper than transverse slopes steeper than shown in IDM Figure 49shown in IDM Figure 49--3A3A

SIDESIDE--DITCH TREATMENTDITCH TREATMENT

Use IDM Fig. 49Use IDM Fig. 49--3B, 493B, 49--3C, or 493C, or 49--3D, depending on ditch3D, depending on ditch--bottom bottom width, to determine if width, to determine if ForeslopeForeslope--BackslopeBackslope combination is CZcombination is CZ--Desirable, Acceptable, or Desirable, Acceptable, or Undesirable.Undesirable.

9

PREFERREDPREFERREDDITCH CROSS SECTIONSDITCH CROSS SECTIONS

SlantSlant--lined arealined area –– Cross section which Cross section which can be traversed by vehicle with can be traversed by vehicle with unrestrained occupantsunrestrained occupantsCrosshatched areaCrosshatched area –– Cross section which Cross section which can be traversed by vehicle with can be traversed by vehicle with restrained occupantsrestrained occupantsLight unlined areaLight unlined area –– Cross section Cross section undesirable for traversing by vehicles in undesirable for traversing by vehicles in general (minor encroachment into area general (minor encroachment into area permissible) permissible)

PREFERREDPREFERREDDITCH CROSS SECTIONSDITCH CROSS SECTIONS

Embankment slopes steeper than Embankment slopes steeper than 4:1, especially 3:1 or steeper 4:1, especially 3:1 or steeper ––Severely limit range of Severely limit range of backslopesbackslopesavailable for safe traversing of available for safe traversing of ditch (may result in vehicle ditch (may result in vehicle rollover if soft or rutted rollover if soft or rutted embankment)embankment)

10

SIDESIDE--DITCH TREATMENTDITCH TREATMENT

If If ForeslopeForeslope--BackslopeBackslope combination combination is in the Undesirable Area of the is in the Undesirable Area of the appropriate Figure, treat the ditch appropriate Figure, treat the ditch as follows:as follows:

Undesirable Undesirable SideSide--Ditch Slopes in CZDitch Slopes in CZ

ADDITIONAL R/W IS AVAILABLEADDITIONAL R/W IS AVAILABLEFlatten one or both ditch side Flatten one or both ditch side slopes to bring into Desirable or slopes to bring into Desirable or Acceptable AreaAcceptable AreaMove ditch bottom outside of CZMove ditch bottom outside of CZ

Undesirable Undesirable SideSide--Ditch Slopes in CZDitch Slopes in CZ

ADDITIONAL R/W NOT AVAILABLEADDITIONAL R/W NOT AVAILABLEPlace a pipe in the ditch line and Place a pipe in the ditch line and fill over itfill over itPlace uniform riprap in the ditch Place uniform riprap in the ditch to change cross section to change cross section Shield the ditch. However, a VShield the ditch. However, a V--ditch or 2:1 foreslope will not ditch or 2:1 foreslope will not always require shieldingalways require shieldingRaise grade of ditch if possible Raise grade of ditch if possible

OBSTRUCTIONOBSTRUCTION--FREEFREEZONEZONE

Definition Definition –– Roadside area next to Roadside area next to travelwaytravelway free from hazards and free from hazards and

obstructions.obstructions.

Not the same as CZ.Not the same as CZ.

11

ObstructionObstruction--Free ZoneFree Zone

ObstructionObstruction--Free Zone widths for Free Zone widths for various Functional Classifications, various Functional Classifications, Design Speeds, and Design Speeds, and AADTsAADTs are are shown in proposed new IDM shown in proposed new IDM Figure 55Figure 55--5A(1).5A(1).

APPURTENANCEAPPURTENANCE--FREE AREA FREE AREA IN OBSTRUCTIONIN OBSTRUCTION--FREE ZONEFREE ZONE

Same as for CZ Same as for CZ –– See IDM Figure See IDM Figure 5555--5A5A

12

OBSTRUCTIONOBSTRUCTION--FREE ZONEFREE ZONE

ONON––STREET PARKING AREAS STREET PARKING AREAS ––Similar treatment as with CZSimilar treatment as with CZ

OBSTRUCTIONS OBSTRUCTIONS –– None rising more None rising more than 4 inches above ground or than 4 inches above ground or surrounding surface unless made surrounding surface unless made breakaway or shieldedbreakaway or shielded

OBSTRUCTIONOBSTRUCTION--FREE ZONE FREE ZONE TREATMENT OF OBSTACLESTREATMENT OF OBSTACLES

Similar to CZ obstacle treatmentSimilar to CZ obstacle treatmentRemove or redesignRemove or redesignRelocate outside OFZRelocate outside OFZMake breakawayMake breakawayShieldShieldDelineateDelineate

SHIELDINGSHIELDINGOBSTRUCTIONOBSTRUCTION

OBSTRUCTION SHIELD,OBSTRUCTION SHIELD,OR ROADSIDE BARRIEROR ROADSIDE BARRIER

CONSIDERATIONSCONSIDERATIONSLateral PlacementLateral PlacementLongitudinal Extent, or Length Longitudinal Extent, or Length of Needof NeedExtent of Barrier DeflectionExtent of Barrier DeflectionType of BarrierType of Barrier

13

ROADSIDE BARRIERROADSIDE BARRIERLATERAL PLACEMENTLATERAL PLACEMENT

Lateral PlacementLateral Placement

CONSIDERATIONSCONSIDERATIONSClearance between Clearance between obstruction and barrierobstruction and barrierDesirable shoulder width Desirable shoulder width Probability of vehicle impact Probability of vehicle impact on barrieron barrierTerrain effects on errant Terrain effects on errant vehiclevehicle’’s impacts impactBarrier flare rateBarrier flare rate

Desirable Lateral PlacementDesirable Lateral Placement

New Construction or AADT > New Construction or AADT > 100,000:100,000:

Front Face of barrier is 2 ft Front Face of barrier is 2 ft outside pavedoutside paved--shoulder widthshoulder width

Reconstruction:Reconstruction:Front Face of barrier is 1 ft Front Face of barrier is 1 ft

outside pavedoutside paved--shoulder widthshoulder width

BARRIERBARRIERDEFLECTIONDEFLECTION

14

BARRIER BARRIER LENGTH OF NEED (LENGTH OF NEED (LoNLoN))

LoNLoN = L= LADVADV + L+ LOBSOBS + L+ LOPPOPP

Where:Where:LLADVADV is is LoNLoN in advance of in advance of

obstructionobstructionLLOBSOBS is the obstruction lengthis the obstruction lengthLLOPPOPP is the trailingis the trailing--end length or end length or

the length needed to protect the length needed to protect oppositeopposite--direction trafficdirection traffic

Barrier Length of NeedBarrier Length of Need

In Advance of Obstruction for In Advance of Obstruction for Adjacent TrafficAdjacent Traffic

Graphical Determination, Graphical Determination, Tangent Section or Inside Tangent Section or Inside Horizontal CurveHorizontal CurveGraphical Determination, Graphical Determination, Outside Horizontal CurveOutside Horizontal CurveMathematical Determination, Mathematical Determination, Tangent Section OnlyTangent Section Only

Barrier Length of NeedBarrier Length of NeedMinimum Minimum LoNLoN for Adjacent Trafficfor Adjacent TrafficRequired Required LoNLoN for Opposing Trafficfor Opposing Traffic

For Design Speed For Design Speed ≥≥ 50 mph, 50 mph, minimum is calculated length or minimum is calculated length or 100 ft, whichever is greater.100 ft, whichever is greater.

For Design Speed For Design Speed ≤≤ 45 mph, 45 mph, minimum is calculated length or 50 minimum is calculated length or 50 ft, whichever is greater.ft, whichever is greater.

15

Barrier LengthBarrier LengthOf NeedOf Need

EXAMPLEEXAMPLE

LengthLength--ofof--Need ExampleNeed ExampleNew ConstructionNew ConstructionTwoTwo--Lane, TwoLane, Two--Way RouteWay RouteDesign Speed: 60 mphDesign Speed: 60 mphAADT = 7000AADT = 7000RightRight--Side Shoulder Width: 10 ftSide Shoulder Width: 10 ftHighHigh--FillFill--Area Area SideslopeSideslope of 2.5:1of 2.5:1Tangent Alignment in Level TerrainTangent Alignment in Level Terrain

LoNLoN EXAMPLEEXAMPLELateral PlacementLateral PlacementSince this is new construction, the Since this is new construction, the front face of the barrier is 2 ft front face of the barrier is 2 ft outside the edge of the paved outside the edge of the paved shoulder.shoulder.

1010--ft Paved ft Paved ShldShld. + 2. + 2--ft Offset =ft Offset =FF at 12 ft outside of travel FF at 12 ft outside of travel lane edgelane edge

LoNLoN DeterminationDeterminationDetermine CZ width from IDM Determine CZ width from IDM Figure 49Figure 49--2A, Clear2A, Clear--Zone Zone Distances (ft), New Construction Distances (ft), New Construction / Reconstruction/ Reconstruction

16

LoNLoN DeterminationDeterminationFrom IDM Fig. 49From IDM Fig. 49--2A, Clear2A, Clear--Zone Width, Line Zone Width, Line CPCP = 30 ft = 30 ft from edge of travel lane, based from edge of travel lane, based on relatively flat (6:1) slope on relatively flat (6:1) slope beyond beyond foreslopeforeslope..

LoNLoN DeterminationDetermination

Determine Determine RunoutRunout Length, Length, LLRR, , from IDM Figure 49from IDM Figure 49--5F, Design 5F, Design Elements for Barrier Length of Elements for Barrier Length of NeedNeed

17

From IDM Fig. 49From IDM Fig. 49--5F, 5F, RunoutRunoutLength Length LLRR, Line , Line PRPR = 340 ft.= 340 ft.

Determine Starting Point of Determine Starting Point of Barrier, Barrier, FF, from IDM Fig. 49, from IDM Fig. 49--4F, Barrier Warrant for 4F, Barrier Warrant for Embankments (60 mph)Embankments (60 mph)

18

Interpolation between the Interpolation between the 6000 and 12,000 AADT lines 6000 and 12,000 AADT lines yields Fill Height of 8.3 ft.yields Fill Height of 8.3 ft.

The longitudinal point The longitudinal point where this occurs where this occurs

corresponds to where the corresponds to where the transverse distance from transverse distance from

the shoulder break line to the shoulder break line to the toe of slope isthe toe of slope is(2.5)(8.3) = 20.8 FT.(2.5)(8.3) = 20.8 FT.

At Point At Point FF, where fill is, where fill is8.3 ft high, scale the 8.3 ft high, scale the LLRRdistance of 340 ft along distance of 340 ft along Line Line PRPR..

19

Draw Hypotenuse Draw Hypotenuse CRCR..

Draw a line, along the face Draw a line, along the face of the barrier from Point of the barrier from Point FF

to where it crosses to where it crosses Hypotenuse Hypotenuse CRCR, at Point , at Point NN..

This line, FN, is the Length This line, FN, is the Length of Need required to shield of Need required to shield traffic from the fill height.traffic from the fill height.

20

LoNLoN, the length of Line , the length of Line FNFN, , can be calculated by can be calculated by proportioning as follows:proportioning as follows:

CF [18 ft]CF [18 ft] = __= __FN____FN____CP [30 ft]CP [30 ft] PR [340 ft]PR [340 ft]

FNFN, or , or LoNLoN, therefore is, therefore is264 ft.264 ft.

21

TYPES OFTYPES OFROADSIDE BARRIERSROADSIDE BARRIERS

Roadside barrier types are Roadside barrier types are based on National based on National

Cooperative Highway Cooperative Highway Research Program Report Research Program Report

350 (NCHRP 350) Test Levels350 (NCHRP 350) Test Levels

Passage of anPassage of anNCHRP 350 Crash TestNCHRP 350 Crash Test

This consists of a given deviceThis consists of a given device’’s s ability to contain and redirect the ability to contain and redirect the test vehicle.test vehicle.The vehicle has remained upright The vehicle has remained upright throughout the test.throughout the test.After impact and stopping, the After impact and stopping, the vehicle is pointing in its original vehicle is pointing in its original direction in its original traffic lane.direction in its original traffic lane.

22

TLTL--3 BARRIERS3 BARRIERS

WW--Beam Guardrail, 6Beam Guardrail, 6’’--33”” Posts Posts SpacingSpacingUsed where clearance between Used where clearance between front guardrail face and front guardrail face and obstruction is 3 ft or greater.obstruction is 3 ft or greater.


WW--Beam Guardrail, 3Beam Guardrail, 3’’--11½”½” Posts Posts SpacingSpacingUsed where clearance between Used where clearance between front guardrail face and front guardrail face and obstruction is at least 2 ft but obstruction is at least 2 ft but less than 3 ft.less than 3 ft.


WW--Beam Guardrail, 1Beam Guardrail, 1’’--66¾”¾” Posts Posts SpacingSpacingUsed where clearance between Used where clearance between front guardrail face and front guardrail face and obstruction is at least 1.25 ft obstruction is at least 1.25 ft but less than 2 ft.but less than 2 ft.


Nested WNested W--Beam Guardrail, any Beam Guardrail, any of the nonof the non--nested post nested post spacingsspacings just indicatedjust indicatedUsed at a large drainage Used at a large drainage structure structure where too little where too little cover atop such cover atop such structure structure precludes driving guardrail precludes driving guardrail posts.posts.

23


DoubleDouble--Faced WFaced W--Beam Beam Guardrail , 6Guardrail , 6’’--33”” Posts SpacingPosts SpacingUsed on a divided roadway as Used on a divided roadway as a a medianmedian--side bridgeside bridge--approach approach guardrail to one of the bridge guardrail to one of the bridge structures in a set of twins.structures in a set of twins.


WireWire--Rope Safety BarrierRope Safety BarrierUsed where the clearance Used where the clearance between the barrier and the between the barrier and the obstruction is at least 10 ft.obstruction is at least 10 ft.

THIS IS NOT YET AN INDOTTHIS IS NOT YET AN INDOT--APPROVED SYSTEM. IT IS APPROVED SYSTEM. IT IS BEING USED ONLY IN BEING USED ONLY IN SELECTED EXPERIMENTAL SELECTED EXPERIMENTAL LOCATIONS.LOCATIONS.


ThrieThrie--Beam Guardrail, 6Beam Guardrail, 6’’--33””Posts SpacingPosts SpacingNew Facility: available New Facility: available deflection distance of at least deflection distance of at least 3 ft, on tangent or on 3 ft, on tangent or on horizontal curve of radius of horizontal curve of radius of 1435 ft or greater, such that:1435 ft or greater, such that:

Barrier is warranted; andBarrier is warranted; andDesignDesign--year AADT year AADT ≥≥ 100,000.100,000.

TLTL--4 BARRIERS4 BARRIERSThrieThrie--Beam Guardrail, 6Beam Guardrail, 6’’--33”” Posts Posts SpacingSpacingNew Facility: available deflection New Facility: available deflection distance of at least 3 ft, on distance of at least 3 ft, on horizontal curve of radius of less horizontal curve of radius of less than 1435 ft, such that:than 1435 ft, such that:

Barrier is warranted;Barrier is warranted;Design speed 50 mph or higher; Design speed 50 mph or higher; andandDesignDesign--year AADT year AADT ≥≥ 10,000.10,000.

24


ThrieThrie--Beam Guardrail, 6Beam Guardrail, 6’’--33””Posts SpacingPosts Spacing4R or 3R Work: available 4R or 3R Work: available deflection distance of at least deflection distance of at least 3 3 ft, on tangent or on ft, on tangent or on horizontal curve of radius of horizontal curve of radius of 1435 ft or greater1435 ft or greater

TLTL--4 BARRIERS4 BARRIERSThrieThrie--Beam Guardrail, 6Beam Guardrail, 6’’--33”” Posts Posts SpacingSpacing

4R or 3R Work: 4R or 3R Work: Barrier is in place, but must be Barrier is in place, but must be moved transversely to moved transversely to accommodate lanes or shoulders accommodate lanes or shoulders widened, or horizontal curves widened, or horizontal curves improved, to 3R standards, and improved, to 3R standards, and barrier is still warranted; andbarrier is still warranted; andDesignDesign--year AADT year AADT ≥≥ 100,000.100,000.


ThrieThrie--Beam Guardrail, 6Beam Guardrail, 6’’--33””Posts SpacingPosts Spacing4R or 3R Work: available 4R or 3R Work: available deflection distance of at least deflection distance of at least 3 3 ft, on horizontal curve of ft, on horizontal curve of radius of less than 1435 ft.radius of less than 1435 ft.

TLTL--4 BARRIERS4 BARRIERSThrieThrie--Beam Guardrail, 6Beam Guardrail, 6’’--33”” Posts Posts SpacingSpacing

4R or 3R Work: 4R or 3R Work: Barrier is in place, but must be Barrier is in place, but must be

moved transversely to moved transversely to accommodate lanes or shoulders accommodate lanes or shoulders widened, or horizontal curves widened, or horizontal curves improved, to 3R standards, and improved, to 3R standards, and barrier is still warranted;barrier is still warranted;

Design speed 50 mph or higher; andDesign speed 50 mph or higher; andDesignDesign--year AADT year AADT ≥≥ 10,000.10,000.

25

TLTL--4 BARRIERS4 BARRIERSThrieThrie--Beam Guardrail, 6Beam Guardrail, 6’’--33”” Posts Posts SpacingSpacingPartial 3R Work:Partial 3R Work:

Guardrail currently in place;Guardrail currently in place;Guardrail still warranted; andGuardrail still warranted; andA guardrail run has been A guardrail run has been

damaged, or gets impacted, on damaged, or gets impacted, on average, 2 or more times per year.average, 2 or more times per year.


Concrete Shape F, 2Concrete Shape F, 2’’--99””Common HeightCommon Height

Zero deflection distance Zero deflection distance available.available.Most typical use is on an Most typical use is on an urban freeway where a urban freeway where a barrier is warranted.barrier is warranted.

The only TLThe only TL--5 Barrier is 5 Barrier is Concrete, Shape F,Concrete, Shape F,33’’--99”” Truck HeightTruck Height

TLTL--5 BARRIER5 BARRIER

Radius of less than 1435 ftRadius of less than 1435 ftUndercrossingUndercrossing route, or parallel route, or parallel route below within 120 ft of route below within 120 ft of overhead travel lane, has overhead travel lane, has designdesign--year AADT year AADT ≥≥ 75007500An errant truck would violate An errant truck would violate a TLa TL--3 or TL3 or TL--4 device, and 4 device, and reach the reach the undercrossingundercrossing or or lower parallel routelower parallel route

26

GUARDRAILGUARDRAILEND TREATMENTSEND TREATMENTS

((GRETsGRETs))

Guardrail End TreatmentsGuardrail End Treatments

TLTL--3 TREATMENTS3 TREATMENTSDesign speed for Test Level 3 is 60 Design speed for Test Level 3 is 60 mph. Test Level 3 is acceptable for mph. Test Level 3 is acceptable for a wide range of higha wide range of high--speed speed highways.highways.

TLTL--3 3 GRETsGRETs

Type OS Type OS –– Outside ShoulderOutside ShoulderDissipates energy when hit headDissipates energy when hit head--on. on. Can redirect errant vehicle on one Can redirect errant vehicle on one side only.side only.Used with singleUsed with single--faced guardrail.faced guardrail.Proprietary device.Proprietary device.

TYPE OS

27

GUARDRAIL END TREATMENT TYPE OS

SKT-350

GUARDRAIL END TREATMENT TYPE OSSKT-350 AFTER CRASH-TEST IMPACT

GRET Type OSGRET Type OS

A 37A 37’’--66”” portion of the downstream portion of the downstream end can function as guardrail. It end can function as guardrail. It may be applied to the guardrailmay be applied to the guardrail’’s s lengthlength--ofof--need requirement.need requirement.


Type MS Type MS –– Median ShoulderMedian ShoulderDissipates energy when hit headDissipates energy when hit head--on.on.Can redirect errant vehicle on two Can redirect errant vehicle on two sides.sides.Used with doubleUsed with double--faced guardrail.faced guardrail.Proprietary device.Proprietary device.

28

GUARDRAIL END TREATMENT TYPE MSCAT-350

GUARDRAIL END TREATMENT TYPE MSFLEAT-MT 350


Type OS or MS proprietary devices Type OS or MS proprietary devices are chosen by the contractor from are chosen by the contractor from the Departmentthe Department’’s Approved List of s Approved List of Guardrail End TreatmentsGuardrail End Treatments

29

GRET Type MSGRET Type MS

A 12A 12’’--66”” portion of the downstream portion of the downstream end can function as guardrail. It end can function as guardrail. It may be applied to the guardrailmay be applied to the guardrail’’s s lengthlength--ofof--need requirement.need requirement.

TLTL--3 3 GRETsGRETsType IIType II–– Functions like GRET Type OSFunctions like GRET Type OS

Used where cut slopes or Used where cut slopes or backslopesbackslopesabove the roadway grade are above the roadway grade are encountered.encountered.Can redirect errant vehicle on one Can redirect errant vehicle on one side side only.only.Approach Approach foreslopeforeslope must be 4:1 or must be 4:1 or flatter.flatter.Not proprietary .Not proprietary .

NonNon--NCHRPNCHRP--350 GRET350 GRET

Type IType IUsed only on a localUsed only on a local--agency agency route, or a local agencyroute, or a local agency’’s s approach to an INDOT route.approach to an INDOT route.LocalLocal--agencyagency--route AADT route AADT ≤≤ 400.400.No federal participation in No federal participation in funding.funding.Not proprietary.Not proprietary.

IMPACTIMPACTATTENUATORSATTENUATORS

30

Impact AttenuatorsImpact AttenuatorsAll Impact Attenuators are NCHRP 350 Test All Impact Attenuators are NCHRP 350 Test Level 1, Test Level 2, or Test Level 3 Level 1, Test Level 2, or Test Level 3 devices, and are all proprietary.devices, and are all proprietary.Design speed for Test Level 1 is 30 mph or Design speed for Test Level 1 is 30 mph or lower.lower.Design speed for Test Level 2 is 45 mph or Design speed for Test Level 2 is 45 mph or lower.lower.Design speed for Test Level 3 is 60 mph. Design speed for Test Level 3 is 60 mph. Test Level 3 is acceptable for a wide range Test Level 3 is acceptable for a wide range of highof high--speed highways.speed highways.

IMPACT ATTENUATORSIMPACT ATTENUATORSImpact attenuators are used to shield barriers under theImpact attenuators are used to shield barriers under thefollowing conditions:following conditions:For the terminal end of a concrete median barrier, an For the terminal end of a concrete median barrier, an impact attenuator R1 or R2 is typically used.impact attenuator R1 or R2 is typically used.If truckIf truck--height barrier does not connect to the commonheight barrier does not connect to the common--height concrete barrier, the ends must be tapered down theight concrete barrier, the ends must be tapered down to o the commonthe common--height concrete barrier and terminated with height concrete barrier and terminated with an appropriate impact attenuator.an appropriate impact attenuator.At the end of truckAt the end of truck--height concrete bridge railing.height concrete bridge railing.Pier located on median side on multiPier located on median side on multi--lane divided roadway lane divided roadway with single or twin overhead structures.with single or twin overhead structures.Space limitations for barrier transition length plus guarSpace limitations for barrier transition length plus guardrail drail end treatment length, where the barrier end must be end treatment length, where the barrier end must be shielded.shielded.

TYPES OFTYPES OFIMPACTIMPACT

ATTENUATORSATTENUATORS

Type EDType EDEDED stands for stands for EEnergy nergy DDissipation. This is issipation. This is a nona non--redirectiveredirective energy dissipation energy dissipation device. It consists of a number of graveldevice. It consists of a number of gravel--filled modules that are installed in a filled modules that are installed in a specific geometric array in front of a specific geometric array in front of a hazard. As the impacting vehicle passes hazard. As the impacting vehicle passes through the array, its speed is slowed by through the array, its speed is slowed by transfer of its momentum to the gravel, transfer of its momentum to the gravel, allowing for controlled safe, steady allowing for controlled safe, steady deceleration. deceleration.

31

IMPACT ATTENUATOR TYPE EDGRAVEL BARRELS

IMPACT ATTENUATOR TYPE EDCAT-350

Type R1Type R1

R1R1 stands for stands for RRedirectiveedirective on on 11 side. side. This is an energy dissipator with This is an energy dissipator with redirectiveredirective capability on only one capability on only one side.side.

Type R2Type R2

R2R2 stands for stands for RRedirective on edirective on 22sides. This is an energy dissipator sides. This is an energy dissipator with redirective capability on two with redirective capability on two sides.sides.

32

IMPACT ATTENUATOR TYPE R1 OR R2QUADGUARD

IMPACT ATTENUATOR TYPE R1 OR R2REACT-350

IMPACT ATTENUATOR TYPE R1 OR R2TAU-II

Type CRType CR

CRCR stands for stands for CClearance learance RRestriction. estriction. It is an energy It is an energy dissipatordissipator with with redirectiveredirective capability on two sides. capability on two sides. It is used where lateral clearance It is used where lateral clearance restrictions make installation and restrictions make installation and maintenance difficult.maintenance difficult.

33

IMPACT ATTENUATOR TYPE CR REACT-350

Type SDType SD

SDSD stands for vertical stands for vertical SSight ight DDistance istance limitation. It is an energy limitation. It is an energy dissipatordissipatorwith with redirectiveredirective capability on two capability on two sides. It is used at an intersection sides. It is used at an intersection where sight distance would be where sight distance would be limited if a taller attenuator were limited if a taller attenuator were used.used.

Type LSType LS

LSLS stands for stands for LLow ow SSpeed energy peed energy dissipation device. It has dissipation device. It has redirectiveredirective capability on two sides, capability on two sides, and shall be used in accordance and shall be used in accordance with TLwith TL--1 criteria only. Type LS 1 criteria only. Type LS should be selected for a design should be selected for a design speed of 30 mph or lower.speed of 30 mph or lower.

Impact AttenuatorsImpact Attenuators

Since these are proprietary devices, Since these are proprietary devices, they are chosen by the contractor they are chosen by the contractor from the Departmentfrom the Department’’s Approved List s Approved List of Impact Attenuators.of Impact Attenuators.

34

Attenuator WidthAttenuator Width

The attenuator width is based on The attenuator width is based on the obstruction width.the obstruction width.


Available Standard WidthsAvailable Standard Widths

W1: Obstruction W1: Obstruction ≤≤ 3 ft wide.3 ft wide.W2: 3 ft < Obstruction Width W2: 3 ft < Obstruction Width ≤≤ 6 ft.6 ft.W3: 6 ft < Obstruction Width W3: 6 ft < Obstruction Width ≤≤ 8 ft.8 ft.


Type ED is available as W1 only.Type ED is available as W1 only.Type R1 or R2 should be used if Type R1 or R2 should be used if W2 or W3 is required.W2 or W3 is required.Type LS is available as W1 only. Type LS is available as W1 only. Type R2 or CR should be used if Type R2 or CR should be used if W2 or W3 is required.W2 or W3 is required.

35


If W3 is not sufficient,If W3 is not sufficient,attenuator with > 8 ft width must attenuator with > 8 ft width must be designed and constructed;be designed and constructed;obstruction width must be altered obstruction width must be altered to accommodate W3; or to accommodate W3; or obstruction must be removed.obstruction must be removed.

CLEAR-ZONE / 1. Trees and shrubs 3350 OBSTRUCTION-FREE ...

Documents

Transcript of CLEAR-ZONE / 1. Trees and shrubs 3350 OBSTRUCTION-FREE ...