Embed Size (px)
Citation preview
Roundabout Capacity Analysis
NEW YORK STATE DEPARTMENT OF TRANSPORTATION
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
RODEL / ARCADY
SYNCHRO 6, 7
Results of NCHRP 3-65, Report 572
VISSIM
PARAMICS
Two Types of Capacity Prediction Models
Empirical
RODEL or ARCADY Based on field
measurements, not theory
Capacity measured during “at capacity” operation in U.K.
Gap Theory
SIDRA, SYNCHRO, VISSIM, Paramics Theoretical Capacity “Seeing is believing”
Note: They can give very different results
Single Lane FHWA Study
Dual (2) Lane FHWA Study – programs still do not agree
SIDRA
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 Concerns over high capacity predictions
with low circulating flows can be resolved – use 1.2 Environment Factor:
SIDRA USER 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
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
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
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
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…
Geometric Parameters
Effective Geometric Parameters
V = Approach Roadway Width
E = Entry Width
L’ = Effective Flare Length
D = Inscribed Circle Diameter
R = Entry Radius
Phi = Entry angle
RODEL = ROundabout DELay
RODEL USER 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
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
Remember leg from the north…
RODEL – Future Desires
To have better controlover input widths – a few organizationshave already developed “default” geometric inputs
SYNCHRO / SimTraffic 6, 7 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 6 clip – Multi-Lane Roundabout Think about which lanes go where…
SimTraffic 7 clip – Multi-Lane Roundabout3D simulation goes a long way with
convincing decision makers & John Q. Public
SYNCHRO / SimTraffic USER 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
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
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 – Single Laners
NCHRP 3-65 – Report 572 – Delay & Queue
NCHRP 3-65 – Report 572 – Two Laners
NCHRP 3-65 - Report 572 USER 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
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
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 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 – showing signalized ped crossings
VISSIM Clip – using Level 1 - $2000
VISSIM Clip – shows overall improvements
VISSIM Clip – using Level 2 - $3000 more
Using 3D Studio Max with VISSIMThis 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 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
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 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 – costs around $12,000
Paramics Clip
PARAMICS – arrows show allowed movements
PARAMICS – like VISSIM – will demonstrate “Too Fast Too Furious” driving behavior
PARAMICS USER – years ago anyway 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
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 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 is 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 “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 -Not 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 – 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 NYSDOTThe NYSDOTRoundabout Design Unit Roundabout Design Unit
would like to thank everyone would like to thank everyone for their attention this for their attention this
morning…morning…
NYSDOT Roundabout Design Unit Contact 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]
