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NEW YORK STATE DEPARTMENT OF TRANSPORTATION. Roundabout Capacity Analysis. My, not necessarily NYSDOT’s, opinion of most of the commonly used programs throughout the US from an actual user and reviewer perspective. Roundabout Capacity Software. SIDRA Intersection

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Roundabout capacity analysis

NEW YORK STATE DEPARTMENT OF TRANSPORTATION

Roundabout Capacity Analysis


My, not necessarily NYSDOT’s, opinion of most of the commonly used programs throughout the US from an actual user and reviewer perspective


Roundabout Capacity Software commonly used programs throughout the US from an actual user and reviewer perspective

  • SIDRA Intersection

  • RODEL / ARCADY

  • SYNCHRO 6, 7

  • Results of NCHRP 3-65, Report 572

  • VISSIM

  • PARAMICS


Two Types of Capacity Prediction Models commonly used programs throughout the US from an actual user and reviewer perspective

Gap Theory

  • SIDRA, SYNCHRO, VISSIM, Paramics

    • Theoretical Capacity

    • “Seeing is believing”

Empirical

  • RODEL or ARCADY

    • Based on field measurements, not theory

    • Capacity measured during “at capacity” operation in U.K.

Note: They can give very different results


Single lane fhwa study
Single Lane FHWA Study commonly used programs throughout the US from an actual user and reviewer perspective


Dual 2 lane fhwa study programs still do not agree
Dual (2) Lane FHWA Study – commonly used programs throughout the US from an actual user and reviewer perspectiveprograms still do not agree


SIDRA commonly used programs throughout the US from an actual user and reviewer perspective

  • Developed in Australia

  • Gap theory analysis

  • Geometric parameters partially considered

  • Used by about 80% of the country

  • Does signals, most other intersections also

  • Calculates emissions – CMAQ money… 


SIDRA – pre-Version 3 commonly used programs throughout the US from an actual user and reviewer perspective

  • Concerns over high capacity predictions with low circulating flows can be resolved – use 1.2 Environment Factor:


SIDRA USER commonly used programs throughout the US from an actual user and reviewer perspective

  • Quite user friendly – quick & easy to follow

  • Movement displays are nice for design reports

  • Data easily extracted from results

    SIDRA REVIEWER

  • Lots of output to review

  • Quite a few “defaults” can be altered to manipulate results

  • Really want actual file

  • Some user error is possible


SIDRA – Future Desires commonly used programs throughout the US from an actual user and reviewer perspective

  • To go froma display thatgives general movementdata:

    to a display that gives conflict totals per lane crossing locations or at least per lane on approach & circulating

  • Also, export displays


RODEL – similar to ARCADY commonly used programs throughout the US from an actual user and reviewer perspective

  • Developed in Great Britain

  • Empirical analysis

  • Geometric parameters considered

  • Used by about 30% of the country

  • D.O.S. based

  • Metric Only

  • Only models roundabouts

  • RODEL 2 (Arcady 7) is here…  for info see:

  • http://teachamerica.com/RAB08/RAB08S5BJohnson/index.htm


Why Roundabouts Re-emerged commonly used programs throughout the US from an actual user and reviewer perspective

  • Research on 35 geometric variations

  • Many roundabouts were rehabilitated and new sites were considered

  • Follow up study confirmed the capacity prediction equations were valid

TRL study test track (U.K.) - 1968


Empirical Model commonly used programs throughout the US from an actual user and reviewer perspective

  • Strongly relates capacity to detailed geometry

  • Accidents also directly related to geometry

  • Great tool for the design engineer

  • Helps find the “optimum” geometry


Capacity of an Approach – not lane by lane… commonly used programs throughout the US from an actual user and reviewer perspective


Geometric Parameters commonly used programs throughout the US from an actual user and reviewer perspective


Effective Geometric Parameters commonly used programs throughout the US from an actual user and reviewer perspective

V = Approach Roadway Width

E = Entry Width

L’ = Effective Flare Length

D = Inscribed Circle Diameter

R = Entry Radius

Phi = Entry angle


RODEL = ROundabout DELay commonly used programs throughout the US from an actual user and reviewer perspective


RODEL USER commonly used programs throughout the US from an actual user and reviewer perspective

  • User friendly – but need to understand design

  • Instantly see results from geometric revisions

  • 1 input screen is all you need

    RODEL REVIEWER

  • 1 screen capture is all you need

  • No real “defaults” that can be altered to manipulate results

  • Can’t really go from RODEL to CAD file

  • User error is common

  • Really need to understand design


RODEL – Future Desires commonly used programs throughout the US from an actual user and reviewer perspective

  • To be able to analyze lane by lane – unbalanced lane use, assumption of circulating lanes, and compounding lefts cause questionable results currently


RODEL = ROundabout DELay commonly used programs throughout the US from an actual user and reviewer perspective

Remember leg from the north…


RODEL – Future Desires commonly used programs throughout the US from an actual user and reviewer perspective

  • To have better controlover input widths – a few organizationshave already developed “default” geometric inputs


SYNCHRO / SimTraffic 6, 7 commonly used programs throughout the US from an actual user and reviewer perspective

  • Uses HCM 2000 equations

  • Geometric parameters not considered

  • Compared to real sites?

  • Will only analyze single lane roundabouts

    • SIM Traffic will simulate up to 4 laners

  • Doesn’t calculate L.O.S. based on delay

  • Will do most other intersections



SimTraffic 7 clip – Multi-Lane Roundabout which lanes go where…3D simulation goes a long way with convincing decision makers & John Q. Public


SYNCHRO / SimTraffic USER which lanes go where…

  • User friendly for single laners

  • Inputs very similar to that of other intersections

  • Difficult to control lane use within roundabout

    SYNCHRO / SimTraffic REVIEWER

  • Lots of data in output – real worth???

  • Single laners – you need to watch video

  • Multi-Laners – really no good way to review since lane use within roundabout doesn’t follow typical designs


SYNCHRO / SimTraffic – Future Desires which lanes go where…

  • To have LOS based on delay – hopefully the formulas from Report 572 will be incorporated. Currently, good designs get poor LOS because they use 60 to 80% of their capacity. Over-designs are rewarded with better LOS based on ICU…

  • WHAT IS ICU?

  • WHAT DOES “#” MEAN?

  • WHAT DOES “~” MEAN?

  • If you use Synchro to simulate multi-laners please make sure you take the time to read:

  • http://www.trafficware.com/assets/pdfs/Multi-lane%20Roundabouts%20Supplement.pdf


NCHRP 3-65 – Report 572 which lanes go where…

  • National Cooperative Highway Research Program – Applying Roundabouts in the United States

  • Initial project is done, see Report 572

  • FHWA wanted “U.S. program”

  • Equation is best fit to existing US conditions

  • Multi-Lane analysis is based on critical lane

  • Currently working on the next FHWA Roundabout Guide





NCHRP 3-65 - Report 572 USER which lanes go where…

  • User friendly – if you can work a calculator

  • Easy to determine if capacity is there

  • Delay & Queues require a little more time

    NCHRP 3-65 - Report 572 REVIEWER

  • Need to check lane assignments

  • No “defaults” that can be altered to manipulate results

  • User error is eliminated

  • Designer error can still influence results


NCHRP 3-65 – Report 572 – Future Desires which lanes go where…

  • To have a more user-friendly platform

  • To be able to account for unbalanced circulating flows

  • To be able to analyze each approach lane separately

  • To be able to apply to 3 lane roundabouts


Simulation Programs which lanes go where…

  • Not typically used for roundabout design – are being used to visually check predictions – NYSDOT wants to see VISSIM

  • Great tools for Public Info Meetings

  • Able to show network impacts

  • Visually displays improved performance provided by roundabouts

  • VISSIM seems to be more common choice

  • Paramics is comparable but more expensive


VISSIM which lanes go where…

  • Developed in Germany

  • Gap Based – not geometric specific

  • Great tool for Public Info Meetings

  • Able to show network impacts

  • Can visualize impacts from signalized pedestrian crossings… 

  • Does nearly any roadway & intersection configuration possible: like cfi, ddi, spui …



VISSIM Clip – using Level 1 - $2000 which lanes go where…




Using 3D Studio Max with VISSIM which lanes go where…

This video comes from a project in Carmel, Indiana. You might want to put in your paperwork now for the 2011 National Roundabout Conference in Carmel – May 11-13th or so.


VISSIM USER which lanes go where…

  • More time consuming – unless using templates

  • Truck/car interaction can be challenging

  • Excellent control of lane use within roundabout

    VISSIM REVIEWER

  • Output Data isn’t as refined as other programs

  • Time Consuming – you need to watch the video

  • Constant updates – especially when dealing with DOT software installation procedures


VISSIM – Future Desires which lanes go where…

  • To not have vehicles be able to cross through each other – conflict areas???

  • NOTE: Make sure you never have vehicles crossing in your presentation! We do not want to go in front of the public with an actual VISSIM file – video clips are much safer.

  • Standardized “appealing” Output Format


PARAMICS which lanes go where…

  • Developed in Scotland

  • Does have actual roundabout “node”

  • Roundabout “node” does have limitations

  • Great tool for Public Info Meetings

  • Origin-Destination based routing

  • A little bit more expensive than the other programs

  • Steep learning curve



Paramics Clip which lanes go where…




PARAMICS USER – years ago anyway Too Furious” driving behavior

  • More time consuming – especially with non-traditional lane use within roundabout

  • Truck/car interaction can be challenging

  • Decent control of lane use within roundabout

    PARAMICS REVIEWER

  • Output Data isn’t as refined as other programs

  • Time Consuming – you need to watch the video


PARAMICS – Future Desires Too Furious” driving behavior

  • To not have vehicles be able to cross through each other – does not go over well with less than enthused audience

  • Standardized “appealing” Output Format

  • Large Vehicle tracking more realistic

  • Better lane control at approach and within roundabout – sometimes vehicles will realize at the yield line that they needed to be in other lane – could be realistic though… 


Roundabout Capacity Software Too Furious” driving behavior

  • SIDRA Intersection

  • RODEL / ARCADY

  • SYNCHRO 6, 7

  • Results of NCHRP 3-65, Report 572

  • VISSIM

  • PARAMICS

  • ANY OTHERS???

  • Which one (or more) to choose???

  • The next few slides show a “simplified” method used at NYSDOT


The Real Limitation to the Capacity of a Roundabout Too Furious” driving behavioris at the Yield Line

The availability of usable gaps in the circulatory roadway traffic for approaching vehicles trying to enter the roundabout is what truly limits the roundabouts capacity…

THE ACTUAL DESIGN SPECS DON’T REALLY MATTER AS LONG AS IT IS A GOOD DESIGN… 


Quick Capacity Too Furious” driving behavior“Guesstimate” for Single Laner

  • 0 - 750 LOS A

  • 750 - 850 LOS A / B

  • 850 - 950 LOS B / C

  • 950 - 1050 LOS C / D

  • 1050 - 1150 LOS D / E

  • 1150 - 1400 LOS E / F

  • DON’T EXCEED 1400 VPH AT THE CONFLICT POINT FOR A 1 LANER


Capacity Limits - Too Furious” driving behaviorNot Lane by Lane

If sum is 0 – 1,000 then

Single lane works

If sum is 1,000 – 1,300 then

Single lane might work

If sum is 1,300 – 1,800 then

2 laner works

If sum is1,800 – 2,200 then

2 laner might work

If sum is 2,200 – 2,900

3 laner might work


Capacity Limits –Still want to Check Lane by Lane Too Furious” driving behavior – now 900 vphpl is limit

The 1,000 rule of thumb drops to 900 because entering vehicles need to find acceptable gaps in both circulating lanes at once – some gaps in the outer lane will be eliminated by the vehicles circulating in the inner lane….

Potential Capacity Problems


The nysdot roundabout design unit would like to thank everyone for their attention this morning
The NYSDOT Too Furious” driving behaviorRoundabout Design Unit would like to thank everyone for their attention this morning…


Nysdot roundabout design unit contact information
NYSDOT Roundabout Design Unit Too Furious” driving behaviorContact Information

Howard McCulloch, Richard Schell, PE

Michael Houlihan, Greg Bailey

and Tom Kligerman, PE

Roundabout Design Unit

50 Wolf Road, POD 24

Albany, New York 12232

Tel: (518) 485-7503

Fax: (518) 457-2916

E-mail: [email protected]


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