11-dmrb.pdf

NRA TD 41NRA TD 41--42/09 42/09

ATAT--GRADE JUNCTION DESIGNGRADE JUNCTION DESIGN

DMRB Vol 6 – File 11 0

NRA TD 41NRA TD 41--42/0942/09

MAJOR / MINOR PRIORITY JUNCTION & VEHICULAR MAJOR / MINOR PRIORITY JUNCTION & VEHICULAR ACCESS TO NATIONAL ROADSACCESS TO NATIONAL ROADS

DMRB Vol 6 – File 5 1

TABLE OF CONTENTS OF NRA TD 41TABLE OF CONTENTS OF NRA TD 41--42/0942/09

IntroductionIntroduction Layout OptionsLayout Options SitingSiting SafetySafety Provision for NonProvision for Non Motorised UsersMotorised Users Provision for NonProvision for Non--Motorised UsersMotorised Users Landscape & Roadside FeaturesLandscape & Roadside Features Geometric Design for Single Geometric Design for Single cc/w Roads/w Roadsg gg g Geometric Design for Dual Geometric Design for Dual cc/w Roads/w Roads References References

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NRA TD 41NRA TD 41--42/09 42/09 –– INTRODUCTIONINTRODUCTION

Deals with:Deals with: Major/minor priority junctions onto National RoadsMajor/minor priority junctions onto National Roads

VehicularVehicular access onto National Roadsaccess onto National Roads VehicularVehicular access onto National Roadsaccess onto National Roads AspectsAspects of Compact Grade Separation immediately adjacent to of Compact Grade Separation immediately adjacent to

the Mainlinethe MainlineG idG id ‘ ’ d ‘ ’ di t i d R i l d‘ ’ d ‘ ’ di t i d R i l d GuidanceGuidance on ‘x’ and ‘y’ distances as required on Regional and on ‘x’ and ‘y’ distances as required on Regional and Local RoadsLocal Roads

Specifies 3 types of “Direct Access”:Specifies 3 types of “Direct Access”: Direct Access Layout 1 Direct Access Layout 1 –– Field AccessField Access Direct Access Layout 2 Direct Access Layout 2 –– Vehicular Access to 1 or more properties Vehicular Access to 1 or more properties

(<150 movements per week)(<150 movements per week) Direct Access Layout 3 Direct Access Layout 3 –– Left in / Left out direct access for use on Left in / Left out direct access for use on

dual dual cc/w/w Junction treatmentJunction treatment to be “Stopto be “Stop” condition onto National Road (may ” condition onto National Road (may

use “Yield” conditions onto Regional & Local Road)use “Yield” conditions onto Regional & Local Road)use Yield conditions onto Regional & Local Road)use Yield conditions onto Regional & Local Road)

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NRA TD 41NRA TD 41--42/09 42/09 –– ACCESS TYPESACCESS TYPES

Direct Access Layout 1 Direct Access Layout 1 –– Field AccessField Access

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Direct Access Layout 2 Direct Access Layout 2 –– Vehicular AccessVehicular Access

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Direct Access Layout 3 Direct Access Layout 3 –– Left In / Left OutLeft In / Left Out

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NRA TD 41NRA TD 41--42/09 42/09 –– JUNCTION TYPESJUNCTION TYPES

Simple TSimple T--JunctionJunction

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Ghost Island JunctionGhost Island Junction

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Single Lane Single Lane DuallingDualling

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CrossroadsCrossroads

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Left Hand Skew JunctionLeft Hand Skew Junction

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Simple Right / Left StaggerSimple Right / Left Stagger

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Major / Minor Priority Junction with Nearside Passing Bay for Roads Major / Minor Priority Junction with Nearside Passing Bay for Roads Without Hard ShouldersWithout Hard Shoulders

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CHOICE OF JUNCTION:CHOICE OF JUNCTION:-- BASIC RULESBASIC RULES

Crossroads:Crossroads:RarelyRarely -- not permitted on Rural Road (Clause 2.34)not permitted on Rural Road (Clause 2.34)

-- only on Urban Singleonly on Urban SingleSimple:Simple:YesYes on Reduced or Standard Single (low flow)on Reduced or Standard Single (low flow)Yes Yes -- on Reduced or Standard Single (low flow)on Reduced or Standard Single (low flow)

-- <300 <300 vehveh/day (2/day (2--way) on minor road andway) on minor road and-- <13,000 <13,000 vehveh/day (2/day (2--way) on major roadway) on major road,, y (y ( y) jy) j-- Nearside Passing Bay option is not to be used on new roads Nearside Passing Bay option is not to be used on new roads (only as a low cost solution on an existing layout)(only as a low cost solution on an existing layout)

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CHOICE OF JUNCTION:CHOICE OF JUNCTION:-- BASIC RULESBASIC RULES

Staggered Junctions:Staggered Junctions: Yes Yes –– on Reduced or Standard Single on Reduced or Standard Single cc/w/w Not applicable on Dual Not applicable on Dual cc/w/w Right / Left staggersRight / Left staggers are preferredare preferred UseUse of Left / Right staggered junctions without ghost island is notof Left / Right staggered junctions without ghost island is not UseUse of Left / Right staggered junctions without ghost island is not of Left / Right staggered junctions without ghost island is not

permittedpermitted

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CHOICE OF JUNCTION :CHOICE OF JUNCTION :-- BASIC RULESBASIC RULES

Ghost Ghost Island:Island: Yes Yes -- on Reduced or Standard Single (higher flows)on Reduced or Standard Single (higher flows) Not applicable to Dual Not applicable to Dual C’wayC’way Not applicable where overtaking opportunities are restricted (an Not applicable where overtaking opportunities are restricted (an

obstruction)obstruction)obstruction)obstruction)

Single Lane Single Lane DuallingDualling:: Not recommended on Single Not recommended on Single C’waysC’ways (Relaxation)(Relaxation) Never on Dual Never on Dual C’wayC’way

Y (2Y (2 l ) D ll ) D l C’C’ Yes (2Yes (2--lane) on Dual lane) on Dual C’wayC’way

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CHOICE OF JUNCTIONCHOICE OF JUNCTION

Figure 2/1:Figure 2/1:Outlines Outlines the procedure for selecting a the procedure for selecting a j ti t d i th l tj ti t d i th l tjunction type and preparing the layout.junction type and preparing the layout.

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CHOICE OF JUNCTIONCHOICE OF JUNCTIONFigure Figure 2/2:2/2:Gives approximate traffic flows on the major andGives approximate traffic flows on the major and minor roads for whichminor roads for whichGives approximate traffic flows on the major andGives approximate traffic flows on the major and minor roads for which minor roads for which each type is appropriate.each type is appropriate.

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JUNCTION JUNCTION LOCATIONSLOCATIONS

Site on non overtaking sectionsSite on non overtaking sections where where possiblepossible Where major road approach gradients are ideally less than 2% Where major road approach gradients are ideally less than 2%

(Cl 3 8)(Cl 3 8)(Clause 3.8)(Clause 3.8) Ghost Islands and Single lane Ghost Islands and Single lane DuallingDualling are “obstructions to are “obstructions to

overtaking”overtaking” Simple junctions are not Simple junctions are not “obstructions to overtaking”“obstructions to overtaking” Ghost Islands on unimproved roads may tempt drivers to overtakeGhost Islands on unimproved roads may tempt drivers to overtake

M t d i bl th i id f hM t d i bl th i id f h Most undesirable on the inside of sharp curvesMost undesirable on the inside of sharp curves

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DIRECT ACCESS OFF NATIONAL ROADS DIRECT ACCESS OFF NATIONAL ROADS –– BASIC RULESBASIC RULES

Ideally there should be no accesses at all from National RoadsIdeally there should be no accesses at all from National Roads If must haveIf must have

Group house accesses together and have one direct accessGroup house accesses together and have one direct access Group house accesses together and have one direct accessGroup house accesses together and have one direct access Close up as many as possibleClose up as many as possible

Accesses should not be across the road from each other / or another Accesses should not be across the road from each other / or another i di dminor roadminor road

Access should not be sited within 90m of a rural roundabout (Clause Access should not be sited within 90m of a rural roundabout (Clause 3.5)3.5)

ff Accesses should not be located within overtaking sections of single Accesses should not be located within overtaking sections of single cc/w roads/w roads

Direct accesses shall not be located on the inside of bends where the Direct accesses shall not be located on the inside of bends where the mainline SSD envelope is outside the mainline road pavementmainline SSD envelope is outside the mainline road pavementmainline SSD envelope is outside the mainline road pavementmainline SSD envelope is outside the mainline road pavement

Direct accesses shall not be located on climbing lane sectionsDirect accesses shall not be located on climbing lane sections

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GEOMETRIC DESIGN OF JUNCTIONSGEOMETRIC DESIGN OF JUNCTIONS

CHAPTER 7 OF CHAPTER 7 OF NRA TD 41NRA TD 41--4242

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VISIBILITY REQUIREMENTS OF JUNCTIONS / DIRECT VISIBILITY REQUIREMENTS OF JUNCTIONS / DIRECT ACCESSACCESS

Geometric Standards for junctions are related to the traffic speed of Geometric Standards for junctions are related to the traffic speed of the major road.the major road.Th l f i ibilit t h f ll SSD (Cl 2 2 f TD9)Th l f i ibilit t h f ll SSD (Cl 2 2 f TD9) The envelope of visibility to have full SSD (Clause 2.2 of TD9).The envelope of visibility to have full SSD (Clause 2.2 of TD9).

Along the Along the Major RoadMajor Road, full SSD is required of the junction (Clause , full SSD is required of the junction (Clause 7.5).7.5).

Along Along the the Minor RoadMinor Road three distinct features for three distinct features for visibility visibility are required are required (Clause 7.6):(Clause 7.6): Full SSD is required of the junction andFull SSD is required of the junction and the “Stopthe “Stop” sign (design” sign (design Full SSD is required of the junction and Full SSD is required of the junction and the Stopthe Stop sign (design sign (design

speed of minor road).speed of minor road). Triangular visibility, 15m back along Minor Road and 15m on both Triangular visibility, 15m back along Minor Road and 15m on both

sides ofsides of the majorthe major roadroadsides of sides of the major the major road.road. Full Visibility over splays defined by set backs ‘X’ distances and ‘Y’ Full Visibility over splays defined by set backs ‘X’ distances and ‘Y’

distances.distances.

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VISIBILITY SPLAYSVISIBILITY SPLAYS

Figure 7/1 shows the three Figure 7/1 shows the three

distinct features along thedistinct features along thedistinct features along thedistinct features along the

Minor RoadMinor Road

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VISIBILITY SPLAYSVISIBILITY SPLAYS

Figure 7/2 Visibility Standards with a Curved Major Road (Para 7.8)Figure 7/2 Visibility Standards with a Curved Major Road (Para 7.8)

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SET BACK ‘X’ DISTANCESET BACK ‘X’ DISTANCE

Measured along centreline of Minor RoadMeasured along centreline of Minor Road Measured back from nearside edge of mainline surfaced road Measured back from nearside edge of mainline surfaced road

(i l di h d t i h d h ld )(i l di h d t i h d h ld )(including hard strip or hard shoulder)(including hard strip or hard shoulder) Desirable ‘X’ distance = 3.0m (9.0m where a ‘Yield’ condition applies)Desirable ‘X’ distance = 3.0m (9.0m where a ‘Yield’ condition applies) Relaxations on the ‘X’ distance are permitted in difficult circumstancesRelaxations on the ‘X’ distance are permitted in difficult circumstancesRelaxations on the X distance are permitted in difficult circumstances Relaxations on the X distance are permitted in difficult circumstances

(Clause 7.7)(Clause 7.7) 2.4m (2.0m for lightly used accesses that are not used by 2.4m (2.0m for lightly used accesses that are not used by

agricultural vehicles (such as field gate) onto Regional / Localagricultural vehicles (such as field gate) onto Regional / Localagricultural vehicles (such as field gate) onto Regional / Local agricultural vehicles (such as field gate) onto Regional / Local Roads)Roads)

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‘Y’ DISTANCE‘Y’ DISTANCE

Design Speed of Major Road(kph)

‘Y’ Distance (m)

506070

7090120

85100120

160215295

Low object height may be taken as 0.6m in difficult circumstancesLow object height may be taken as 0.6m in difficult circumstances Generally no Relaxation on ‘y’ is permitted (urban and other local Generally no Relaxation on ‘y’ is permitted (urban and other local

d ith l d hd ith l d h tt Cl 7 7(Cl 7 7( ))))roads with slow speeds may have oneroads with slow speeds may have one--step step –– Clause 7.7(Clause 7.7(cc)))) Parking of vehicles / obstructions within the splays should be Parking of vehicles / obstructions within the splays should be

prevented.prevented.

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CORNER RADIICORNER RADII (CLAUSE (CLAUSE 7.26)7.26)

WithoutWithout HCV’sHCV’s :: 6m6m -- urbanurbanWithout Without HCV sHCV s :: 6m 6m urbanurban10m 10m -- ruralrural

With With HCV’sHCV’s :: 10m + taper 10m + taper -- urban simpleurban simple15m + taper 15m + taper -- most other typemost other typepp ypyp20m 20m -- larger junctionslarger junctions

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CORNER RADIICORNER RADII AT RURAL SIMPLE JUNCTIONS WITH HCV AT RURAL SIMPLE JUNCTIONS WITH HCV PROVISIONPROVISION

15m radius with tapers of 1:10 over a distance 15m radius with tapers of 1:10 over a distance of 25mof 25m

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CARRIAGEWAY WIDTHS (CLAUSES 7.29 TO 7.60)

Ghost IslandGhost IslandGhost IslandGhost Island

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CARRIAGEWAY WIDTHSCARRIAGEWAY WIDTHS (CLAUSE (CLAUSE 7.30)7.30)

Minor RoadMinor Road

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OTHER GEOMETRIC FEATURESOTHER GEOMETRIC FEATURES

Widening on curves Widening on curves ((7.337.33--36)36) Central islands and tapers Central islands and tapers ((7.377.37--38)38) Right turning and deceleration lengthsRight turning and deceleration lengths (7.40(7.40--41)41) Traffic islands and refuges Traffic islands and refuges ((7.477.47--51)51) Diverging lanes and tapersDiverging lanes and tapers ((7 627 62 69)69) Diverging lanes and tapers Diverging lanes and tapers ((7.627.62--69)69)

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JUNCTIONS ONTO DUAL C/W’s (CHAPTER 8) JUNCTIONS ONTO DUAL C/W’s (CHAPTER 8) –– GENERALGENERAL

In principle, the differences between Single and Dual c/w junctions are:In principle, the differences between Single and Dual c/w junctions are:

Merge tapers are only permitted for use on Dual c/wMerge tapers are only permitted for use on Dual c/w Merge tapers are only permitted for use on Dual c/wMerge tapers are only permitted for use on Dual c/w

Nearside diverge auxiliary deceleration lanes are generally for use on Nearside diverge auxiliary deceleration lanes are generally for use on D l /D l /Dual c/wDual c/w

No gaps and hence no traffic right turns are permitted in the central No gaps and hence no traffic right turns are permitted in the central ff // ( f( f / )/ )reserve of Dual reserve of Dual c/w’sc/w’s (except for Type 3 Dual (except for Type 3 Dual cc/w)/w)

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JUNCTIONS ONTO DUAL C/W’s JUNCTIONS ONTO DUAL C/W’s –– DIVERGE TAPERS & DIVERGE TAPERS & LANESLANES

Nearside diverge tapers to be provided:Nearside diverge tapers to be provided: Where the left turning traffic is greater than 300 AADT orWhere the left turning traffic is greater than 300 AADT or Where the HCV percentage is >20% and the left turning traffic is Where the HCV percentage is >20% and the left turning traffic is

>225 AADT>225 AADT As outlined in Clauses 8.50 to 8.55As outlined in Clauses 8.50 to 8.55As outlined in Clauses 8.50 to 8.55As outlined in Clauses 8.50 to 8.55 Auxiliary lanes to be provided where very heavy turning traffic Auxiliary lanes to be provided where very heavy turning traffic

(Table 8/6 and Clause 8.57)(Table 8/6 and Clause 8.57)

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DIVERGE TAPERSDIVERGE TAPERS

Major Minor Priority Junctions with Nearside Diverging TaperMajor Minor Priority Junctions with Nearside Diverging Taper

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DIVERGE AUXILIARY LANESDIVERGE AUXILIARY LANES

Major Minor Priority Junctions with Nearside Diverging Auxiliary LaneMajor Minor Priority Junctions with Nearside Diverging Auxiliary Lane

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JUNCTIONS WITH DUAL C/W’s JUNCTIONS WITH DUAL C/W’s –– MERGE TAPERSMERGE TAPERS

Merge tapers shall only be used at Dual Merge tapers shall only be used at Dual cc/w junction/w junction Criteria for their provision are outlined in Clause 8.61Criteria for their provision are outlined in Clause 8.61 Auxiliary Merge Lanes shall not be provided unless the AllAuxiliary Merge Lanes shall not be provided unless the All--Purpose Purpose

Dual Dual cc/w design speed is 120kph or it is a Motorway (then in /w design speed is 120kph or it is a Motorway (then in accordance with TD22)accordance with TD22)

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BREAK FOR LUNCHBREAK FOR LUNCH

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