roundabouts part 2 - traffex engineers part 2... · 1 the modern roundabout as a traffic signal...

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THE MODERN ROUNDABOUT AS THE MODERN ROUNDABOUT AS A TRAFFIC SIGNAL A TRAFFIC SIGNAL

ALTERNATIVE ALTERNATIVE –– PART 2PART 2

Presented by Presented by NazirNazir LalaniLalani P.E.P.E.

TraffexTraffex Engineers Inc.Engineers [email protected][email protected]

SignsSigns

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Why is Signing so Important?Why is Signing so Important?

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ROUNDABOUT SIGNING ROUNDABOUT SIGNING CHANGECHANGE

Yield signs mandatoryYield signs mandatory

OneOne--way signs on island (or chevrons)way signs on island (or chevrons)

W1W1--6 large black arrow on yellow background not 6 large black arrow on yellow background not allowed on islandallowed on island

Advance guide signs under developmentAdvance guide signs under development

MUTCD Signing in Section 3BMUTCD Signing in Section 3B--2525

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Typical Signing Layout Typical Signing Layout Source: FHWA Roundabout GuideSource: FHWA Roundabout Guide

Signing for rural and suburbanSource: FHWA Roundabout GuideSource: FHWA Roundabout Guide

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Signing Layout Using Current MUTCD Signing Layout Using Current MUTCD Guidance by NYDOTGuidance by NYDOT

MUTCD Signing in Section 3BMUTCD Signing in Section 3B--2525

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Signing Layout Using Current MUTCD Signing Layout Using Current MUTCD Guidance by NYDOTGuidance by NYDOT

Lane use signageSource: FHWA Roundabout GuideSource: FHWA Roundabout Guide

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Source: Proposed Revisions by MUTCD CommitteeSource: Proposed Revisions by MUTCD Committee

Lane use signage per proposed revisionsLane use signage per proposed revisions

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Right sign at the wrong heightRight sign at the wrong height

WhatWhat’’s wrong here with the signage?s wrong here with the signage?

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These signs shall not be used at a These signs shall not be used at a roundabout to prohibit turning left roundabout to prohibit turning left

into the circular roadwayinto the circular roadway

Proposed Amendment to the MUTCDProposed Amendment to the MUTCD

Diagrammatic destination sign

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Pavement MarkingsPavement Markings

MARKINGSMARKINGS(Proposed MUTCD Revisions)(Proposed MUTCD Revisions)

Yield at entry which gives a vehicle on the Yield at entry which gives a vehicle on the circulatory roadway the rightcirculatory roadway the right--ofof--wayway

Deflection of the approaching vehicle counterDeflection of the approaching vehicle counter--clockwise around the central islandclockwise around the central island

Signing and pavement markings at Signing and pavement markings at roundabouts shall present a consistent roundabouts shall present a consistent message to the road usermessage to the road user

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Continuous concentric lane lines shall not be Continuous concentric lane lines shall not be used within the circulatory roadway used within the circulatory roadway

MultiMulti--lane approaches at roundabouts shall lane approaches at roundabouts shall have lane lineshave lane lines

Bicycle lane markings shall not be provided Bicycle lane markings shall not be provided on the circulatory roadwayon the circulatory roadway

Edge line extensions shall not be placed Edge line extensions shall not be placed across the exits from the circulatory roadwayacross the exits from the circulatory roadway


Use the following web link to access the draft Use the following web link to access the draft proposal for Chapter 3H of the new MUTCD:proposal for Chapter 3H of the new MUTCD:

http://tcd.tamu.edu/documents/tcdhttp://tcd.tamu.edu/documents/tcd--mtc/Chapter_3H.approved_in_General_Session.pmtc/Chapter_3H.approved_in_General_Session.pdfdf

http://mutcd.fhwa.dot.gov/resources/proposed_ahttp://mutcd.fhwa.dot.gov/resources/proposed_amend/mend/

(Disclaimer, it is not official policy so use it at your own risk)

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Striping for a mini-roundaboutSource: FHWA Roundabout GuideSource: FHWA Roundabout Guide

Source: Proposed Revisions by Source: Proposed Revisions by MUTCD CommitteeMUTCD Committee

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Exits at multilane roundabout are Exits at multilane roundabout are problematic and require special treatmentsproblematic and require special treatments

TwoTwo--lane exits have higher crash rateslane exits have higher crash rates

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Approach markings to guide drivers to Approach markings to guide drivers to select correct lane at a multilane roundaboutselect correct lane at a multilane roundabout

Reduction from 2 lanes to 1 lane is much tooReduction from 2 lanes to 1 lane is much tooabruptabrupt

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Approach markings narrowed to a single Approach markings narrowed to a single lane on multilane roadwaylane on multilane roadway

Circulatory road is narrowed to one lane to Circulatory road is narrowed to one lane to guide drivers to select correct laneguide drivers to select correct lane

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Schematic layout for multi-lane roundabout striping

Roundabout in Wisconsin with MUTCD proposed striping

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Keeping markings visible in snowyclimates may be a challenge


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Circulatory road is narrowed to one lane to Circulatory road is narrowed to one lane to guide drivers to select correct laneguide drivers to select correct lane

Exit is narrowed to one lane to restrict the Exit is narrowed to one lane to restrict the inner lane from exitinginner lane from exiting

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Exit is narrowed to one lane to restrict the Exit is narrowed to one lane to restrict the inner lane from exitinginner lane from exiting


TwoTwo--lane lane roundabout with roundabout with

double rightdouble right--turn lanesturn lanes

Narrowed to one Narrowed to one lanelane

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Approach Speed Reduction Approach Speed Reduction StrategiesStrategies

Source: Source: www.roundabouts.uswww.roundabouts.us (Scott Ritchie)(Scott Ritchie)

Highly visible chevron signs provide Highly visible chevron signs provide advance warning of central islandadvance warning of central island

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Circulatory roadway cannot be seenChevrons on splitter island?

Source: Janet Kennedy, Transport Research Laboratory, UK

Transverse yellow bar markingsTransverse yellow bar markingsSource: Source: www.roundabouts.uswww.roundabouts.us (Scott Ritchie)(Scott Ritchie)

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Speed reduction markings Speed reduction markings –– MUTCD 2009MUTCD 2009

BicyclesBicyclesSource: Bicycles at RoundaboutsSource: Bicycles at Roundabouts

State of the Practice (Moule)State of the Practice (Moule)

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Some cyclists use the roadSome cyclists use the road

FHWA Roundabout Guide Bike Ramp DetailFHWA Roundabout Guide Bike Ramp Detail(No longer recommended)(No longer recommended)

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Oregon DOT Oregon DOT Bike Ramp Bike Ramp

DetailDetail

3535°° angle; angle; 1:8 taper, 1:8 taper, located located

after taper after taper startsstarts

Photo of ramp with ODOT design (Bend, Photo of ramp with ODOT design (Bend, Oregon)Oregon)

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Caltrans Bike Ramp DetailCaltrans Bike Ramp Detail

4545°° angle; 15m (50angle; 15m (50’’) taper, located at angle ) taper, located at angle pointpoint

Wallwork Bike Ramp DesignWallwork Bike Ramp Design

4545°° angle; short taper, located in taperangle; short taper, located in taper

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Photo of ramp with Wallwork design (Grand Photo of ramp with Wallwork design (Grand Junction, CO)Junction, CO)

Bicycle lane on perimeter in The Bicycle lane on perimeter in The NetherlandsNetherlands

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PedestriansPedestrians

Vehicles do not yield to pedestriansVehicles do not yield to pedestrians

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How does a blind person cross?How does a blind person cross?

Pedestrians should cross in two stagesPedestrians should cross in two stages

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Crosswalk 1Crosswalk 1--2 vehicle lengths back2 vehicle lengths back

Source: Conflicts and Accidents at Multilane Roundabouts in WASource: Conflicts and Accidents at Multilane Roundabouts in WA(Brian Walsh)(Brian Walsh)

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WellWell--defined crossings; single lane preferreddefined crossings; single lane preferred

One car length from the circulatory roadwayOne car length from the circulatory roadway

Splitter islands; slow speeds/adequate deflectionSplitter islands; slow speeds/adequate deflection

No pedestrian access to central islandNo pedestrian access to central island

Prohibit parking to improve sight distanceProhibit parking to improve sight distance

Signs/landscaping should not block sight distanceSigns/landscaping should not block sight distance

Lighting illuminates roundabout and approachesLighting illuminates roundabout and approaches

PEDESTRIAN FRIENDLY DESIGN:PEDESTRIAN FRIENDLY DESIGN:

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TightTight--exit design shows little benefit for exit design shows little benefit for pedestrians by reducing speedpedestrians by reducing speed

Studies in Europe show that most pedestrian Studies in Europe show that most pedestrian crashes occur at roundabout entriescrashes occur at roundabout entries

NoNo relationship has been reported between relationship has been reported between pedestrian collisions and exit radius.pedestrian collisions and exit radius.

Both British and Australian roundabout collision Both British and Australian roundabout collision studies show significant reduction in pedestrian studies show significant reduction in pedestrian injury and fatal collisions with roundaboutsinjury and fatal collisions with roundabouts

PEDESTRIAN STUDIES:PEDESTRIAN STUDIES:

Pedestrian accident rates increase with traffic Pedestrian accident rates increase with traffic volumes and pedestrian volumesvolumes and pedestrian volumes

As pedestrian/vehicle crossing conflicts increase, As pedestrian/vehicle crossing conflicts increase, crosswalk treatments should be improved crosswalk treatments should be improved

Designed correctly, roundabout exits with less tight Designed correctly, roundabout exits with less tight R3s can improve capacity/reduce vehicle crashes, R3s can improve capacity/reduce vehicle crashes, without increasing exit speeds or harming pedestrianswithout increasing exit speeds or harming pedestrians

U.S. Access Board has continuing concerns about U.S. Access Board has continuing concerns about roundabouts safety for visually impaired roundabouts safety for visually impaired pedestrianspedestrians

PEDESTRIAN STUDIES:PEDESTRIAN STUDIES:

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Exit crash due to overlap at MLR with tight R3 radiusExit crash due to overlap at MLR with tight R3 radius

Source: Alternate Design Methods for Pedestrian Safety atSource: Alternate Design Methods for Pedestrian Safety atRoundabout Entries and Exits (Baranowski)Roundabout Entries and Exits (Baranowski)

Roundabout without landscape stripRoundabout without landscape strip

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Detectable warnings at splitter islandDetectable warnings at splitter islandGrass landscaping provides guidanceGrass landscaping provides guidance

US ACCESS BOARD CONCERNSUS ACCESS BOARD CONCERNSMotorists in the U.S. have a poor yield rate at free Motorists in the U.S. have a poor yield rate at free flow lanes, less than 5 %flow lanes, less than 5 %–– Are there design features or engineering treatments that Are there design features or engineering treatments that

encourage yielding?encourage yielding?

Even when drivers yield, blind pedestrians have Even when drivers yield, blind pedestrians have difficulty detecting the yielddifficulty detecting the yield

Landscaping and other design features should direct Landscaping and other design features should direct blind pedestrians to the crosswalksblind pedestrians to the crosswalks

Information becoming available through new Information becoming available through new researchresearch

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SOURCES OF INFORMATIONSOURCES OF INFORMATION

http://www.accesshttp://www.access--board.gov/publications/roundabouts/bulletin.htmboard.gov/publications/roundabouts/bulletin.htm

http://www.hrsc.unc.edu/pubinfo/APS.htmhttp://www.hrsc.unc.edu/pubinfo/APS.htm

http://www.hrsc.unc.edu/research/human_ped.htmhttp://www.hrsc.unc.edu/research/human_ped.htm

NCHRP Project 3NCHRP Project 3--78 78 -- Crossing Solutions at Roundabouts Crossing Solutions at Roundabouts and Channelized Turn Lanes for Pedestrians with Vision and Channelized Turn Lanes for Pedestrians with Vision Disabilities.Disabilities.

Project began in February 1, 2005Project began in February 1, 2005

Techniques for warning blind pedestriansTechniques for warning blind pedestrians(Session 7 Presentations at Vail Conference)(Session 7 Presentations at Vail Conference)

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Pedestrian crossing at roundabout

Signalized Pedestrian CrossingSignalized Pedestrian Crossing

Pedestrian/bicycle underpass at a Pedestrian/bicycle underpass at a roundaboutroundabout

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IlluminationIllumination

Very poorly illuminated roundabout

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Overhead area wide lighting (not Overhead area wide lighting (not oriented to pedestrians)oriented to pedestrians)

Provide lighting around the circulatory Provide lighting around the circulatory roadway and at crosswalksroadway and at crosswalks

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Illuminate the center island, circulatory road, exit and maneuvering areas ( FHWA-RD-00-067)

Source: FHWA Roundabout GuideSource: FHWA Roundabout Guide

Pedestrian Oriented Street LightingPedestrian Oriented Street Lighting

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Source: Facilities Development Manual (ODOT)Source: Facilities Development Manual (ODOT)

Pedestrian oriented lighting at crosswalksPedestrian oriented lighting at crosswalks

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TrucksTrucks

LeftLeft--turning truck problemturning truck problemSource: FHWA Roundabout GuideSource: FHWA Roundabout Guide

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Inscribed Circle Diameter for TrucksInscribed Circle Diameter for Trucks

Design vehicles for roundaboutsDesign vehicles for roundabouts

Source: Roundabout Design Standards Source: Roundabout Design Standards -- City of Colorado Springs City of Colorado Springs

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Truck Apron DesignTruck Apron DesignSource: WA DOT Design Manual Source: WA DOT Design Manual –– Chapter 915Chapter 915

Height ~ 2Height ~ 2””

Width will depend Width will depend on design on design

vehicle turning radiusvehicle turning radius

Cross section of circulatory roadway with truck Cross section of circulatory roadway with truck apronapron

Source: Caltrans Design Information Bulletin 80Source: Caltrans Design Information Bulletin 80--01: Roundabouts01: Roundabouts

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Rear wheels mount the truck apronRear wheels mount the truck apron

To accommodate trucks, exit needs to be To accommodate trucks, exit needs to be 1717’’ wide so R3 does not govern exit speedwide so R3 does not govern exit speed

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Landscaping/DrainageLandscaping/Drainage

Make the central island more conspicuousMake the central island more conspicuous

Improve the aesthetics of the areaImprove the aesthetics of the area

Minimize introducing hazards to the intersectionMinimize introducing hazards to the intersection

Avoid obscuring roundabout or the signing to the driverAvoid obscuring roundabout or the signing to the driver

Maintain adequate sight distancesMaintain adequate sight distances

Clearly indicate drivers not to pass straight throughClearly indicate drivers not to pass straight through

Discourage pedestrian traffic through the central islandDiscourage pedestrian traffic through the central island

Help visually blind pedestrians find sidewalks/crosswalksHelp visually blind pedestrians find sidewalks/crosswalks

WHY PROVIDE LANDSCAPINGWHY PROVIDE LANDSCAPING

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Source: Modern Roundabouts for Oregon (WSDOT)Source: Modern Roundabouts for Oregon (WSDOT)

Curbing and planting detail

Source: Roundabout Design Standards Source: Roundabout Design Standards -- City of Colorado Springs City of Colorado Springs

Curbing and planting detail

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3030””

4242””

66’’

Source: Source: www.roundabouts.uswww.roundabouts.us (Scott Ritchie)(Scott Ritchie)

Poor sight distance caused by signagePoor sight distance caused by signageon the center islandon the center island

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Source: Source: www.roundabouts.uswww.roundabouts.us (Scott Ritchie)(Scott Ritchie)Landscaping design for roundaboutsLandscaping design for roundabouts

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Sight distance restricted by the Sight distance restricted by the landscapinglandscaping

SPECIALIZED ROUNDABOUT SPECIALIZED ROUNDABOUT OPERATIONSOPERATIONS

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Roundabouts at InterchangesRoundabouts at Interchanges


Two raindrop Two raindrop shaped shaped

roundabouts at roundabouts at a diamond a diamond

interchangeinterchange

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Roundabout at an interchange in Vail, CORoundabout at an interchange in Vail, CO

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Roundabout at an interchangeRoundabout at an interchange

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In SeriesIn Series

Roundabout seriesRoundabout seriesGolden and Avon, COGolden and Avon, CO

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Signalized RoundaboutsSignalized Roundabouts

Signalized roundabout/gyratory

Signals on approaches and on roundaboutSignals on approaches and on roundabout

Scoot operated Scoot operated -- one stop on roundaboutone stop on roundabout

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Turbo RoundaboutsTurbo Roundabouts

Limited capacity single lane roundaboutLimited capacity single lane roundabout

Bad safety record of traffic signalsBad safety record of traffic signals

Standard dual lane roundaboutStandard dual lane roundabout–– often not suited for traffic volumeoften not suited for traffic volume–– weaving difficult on high traffic volumeweaving difficult on high traffic volume

PROBLEM DEFINITION:PROBLEM DEFINITION:

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CONFLICTS COMPARISONCONFLICTS COMPARISON

Dual lane roundabout Dual lane roundabout with 2 dual lane exitswith 2 dual lane exits

12 conflicts + 2 weaving conflicts + 2 cut off conflicts

CONFLICTS COMPARISONCONFLICTS COMPARISON

Turbo Turbo roundaboutroundabout

10 10 conflictsconflicts

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Turbo Turbo roundaboutroundabout

Translation-axis

Develop roundabout with high Develop roundabout with high capacity but keep it safecapacity but keep it safe

Challenge:

No weaving No weaving Yield to no more than two Yield to no more than two laneslanesLow speedsLow speeds

Preconditions:

2/91/9

Raised islandsRaised islandsDrivers must select laneDrivers must select lane

WHAT CAN GO WRONG?WHAT CAN GO WRONG?

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Skid marks provide a hint!Skid marks provide a hint!

And here?And here?

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SOME LESSONS LEARNEDSOME LESSONS LEARNED

Avoid extra wide circular Avoid extra wide circular lanelaneNot Pedestrian OrientedNot Pedestrian Oriented

Inadequate center island signInadequate center island sign

RightRight--turn by pass lanes donturn by pass lanes don’’t work for pedestrianst work for pedestrians

Avoid dual lane entry into Avoid dual lane entry into single lane roundaboutsingle lane roundabout

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New chevron assemblyNew chevron assembly

New Pedestrian SignsNew Pedestrian Signs

How many design errors can you find?How many design errors can you find?

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At night the problems are exacerbated!

SOURCES OF INFORMATIONSOURCES OF INFORMATION

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SOURCESSOURCESRoundabout Guide by FHWARoundabout Guide by FHWA

Florida Roundabout GuideFlorida Roundabout Guide

Section 915 of the WADOT Design ManualSection 915 of the WADOT Design Manual

Oregon Modern Roundabout GuideOregon Modern Roundabout Guide

TRB Roundabout Conference (Vail, 2005) TRB Roundabout Conference (Vail, 2005) http://www.teachamerica.com/roundabouts/ra_conferehttp://www.teachamerica.com/roundabouts/ra_conference.htmnce.htm

Webinar Reference ListWebinar Reference List

MORE INFORMATION WEB SITESMORE INFORMATION WEB SITES

NYSDOTNYSDOTwww.dot.state.ny.us/roundabouts/round.htmlwww.dot.state.ny.us/roundabouts/round.html

Arizona DOTArizona DOTwww.dot.state.az.us/CCPartnerships/Roundabouts/index.aspwww.dot.state.az.us/CCPartnerships/Roundabouts/index.asp

Kansas State UniversityKansas State Universitywww.ksu.edu/roundabouts/www.ksu.edu/roundabouts/

Florida DOTFlorida DOTwww.dot.state.fl.us/safety/ped_bike/brochures/pdf/htrrbt.pdf www.dot.state.fl.us/safety/ped_bike/brochures/pdf/htrrbt.pdf

Maryland DOT www.sha.state.md.us/safety/oots/roundabouts/index.aMaryland DOT www.sha.state.md.us/safety/oots/roundabouts/index.asp sp

Oregon DOTOregon DOTwww.odot.state.or.us/techserv/engineer/pdu/Roundabouts/Rndbt indwww.odot.state.or.us/techserv/engineer/pdu/Roundabouts/Rndbt index.htmex.htm

Federal Highway Administration www.fhwa.dot.gov www.tfhrc.gov/saFederal Highway Administration www.fhwa.dot.gov www.tfhrc.gov/safety/00068.htmfety/00068.htm

Source: NYSDOT SPR CSource: NYSDOT SPR C--0101--47, 200247, 2002--0404

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QUESTIONS ?QUESTIONS ?

roundabouts part 2 - traffex engineers part 2... · 1 the modern roundabout as a traffic signal...

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