Exh 8BCITY OF ATLANTIC BEACH
CITY COMMISSION MEETING
STAFF REPORT
AGENDA ITEM::...
SUBMITTED BY:
DATE:
BACKGROUND:
Roundabout at Five-Way Inter~sect~ion~
Robert S. Kosoy, P.E. ~~"- Q
Director of Public Works
November 14,2003
AGENDA ITEM #8B
NOVEMBER 24, 2003
Since the late 1990's, there have been discussions. about the construction of a roundabout at the
five-way intersection of Plaza, Seminole and Sheny Drive. Staff prepazed maps in 1999 demonstrating
four configurations where a large truck would have conflicts with a 60' diameter roundabout.
Recently, we contacted two engineering firms familiar with the Core City Improvements Project and
asked their traffic engineers to provide a brief report.. Both Paul Vetter, P.E. from Edwazds and Kelcey
(formerly Aikenhead & Odom) and Fraser Howe, P.E. from GAI Consultants were very gracious in
providing the attached reports to the City, at no cost. Both reports indicate difficulties with the site:
the proximity of the driveways, the need to shift the lineaz path of Sherry Drive to Seminole Road
going north, and the five-legs to a proposed roundabout. Both engineers feel that a fire truck could be
accommodated by redoing or relocating the driveway and constructing the outer portion (approximately
8-10') of the roundabout in concrete curb and brickpavers that could be driven upon by a fire truck, as
necessary. Both firms suggested that aerogram called "Autoturn" could be used to simulate these
movements by a fire truck very effectively.
The next step would be to complete a Roundabout Justification Study. This step would compaze the
operation of a roundabout to the current controls,. i.e. stop signs, and estimate the average delay for
vehicles using the intersection. After this step, the traffic engineer will recommend how a roundabout:
would affect the safety of the intersection.
Although both firms could capably handle the project, we feel that based on the initial submittal, GAI's
recent experience designing roundabouts in Florida,. and their involvement with the Core City Project,
that they would be able to minimize costs and provide an innovative design.
RECOMMENDATION: Authorize staff to negotiate with GAI Consultants to complete. a
Roundabout Justification Study, and, if justified, famish a preliminary,
design and cost estimate, for a cost Nof to Exceed $10,000.
BUDGET: Commission to authorize from General Fund.
.ATTACHMENT: Report from Edwards and Kelcey
Report from GAI Consultants
.-
REVIEWED BY CITY MANAGER:
"Nov - 10 03 0 2 : S l p AGENDA ITEM #8B
NOVEMBER 24, 2003
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5730 Bowden Road, Suite 200
Sacksonville, Florida 32216
www.ekcorp.com
Phone 904/636-5432.
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AGENDA ITEM #8B
NOVEMBER 24, 2003
Seminole Road, Sherry Drive and Plaza Ronndabont
I have reviewed the planspresented to me by Bob Kosoy on October 31,.2003 showing
the concept design for a roundabout at the subject location.. The undated 1"=30 scale
plans displayed a roundabout at the subject five-legged intersection with an inscribed
(outside circle) diameter of ] 00 feet; a central island diameter of 60 feet and various
islands channelizing traffic. I have reviewed these plans and offer the following'
comments:..
L The five two-way legs create too many approach roadways to the roundabout and
too many closely-spaced conflicts within the smallest roundabout recommended
by the Federal Highway Administration in their published "Roundabouts: An
Informational Guide". The fire station driveway, although low. volume, adds to
the complexity with asixth leg.
2: The Informational Guide (supported by our experience in roundabout design}
.recommends all approaches to the roundabout align to the center point of the
roundabout to reduce the speed on the approach, eghasize the yield condition,
create. a proper sight angle and align the roadways for good positions entering and
exiting the roundabout. The subject roundabout has two approaches (Sherry
Drive and the westbound approach of Plaza) wherein the approach aligns straight
into the circular roadway and thus encourages higher speeds and disregard for the
yield condition on the approach; the straight through movement on both of these
approacheshas no curve alignment to it. These two approaches could be curved
at the roundabout and aligned at the center of the roundabout; however, with the
small radius of the roundabout there is insufficient room for the five approach
roadways. Holding the outside edge of the roundabout at the fire station driveway
and enlarging the roundabout to the northeast may provide enough length around
the roundabout to fit the five approach roadways. This would require additional
right ofway.
3. The best solution to retain the roundabout would be to relocate Seminole Road to
intersect Sherry Drive approximately 180 feet from the centerline of Plaza and
eliminate the approach to the roundabout. The roundabout should then be moved
to be centered on the intersection of the centerlines of Sherry Drive/Seminole
Road North and Plaza and redesigned with four. approaches. The alternative
would provide the best condition and location for the roundaboutbut would
requite right of way and property acquisiton.
4. A further study should be conducted for the roundabout to include a
traffic/capacity analysis using aaSIDRA sofrware and a concept design
investigation of the alternatives, ineludin -right of way acquisition.
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NOV-07-2003 FRI 04 ~ 26 PN GAI CONSULTANTS S, E, FAX N0. 9078431070 acENna ITEM #ss
NOVEMBER 24, 2003
T RAN S M t T T A L
.r~: Bob xosa,~
Company: ity of Atlantic Reach ,,,_
Phone "'-
From:
Date: 11/7/2003 ..__
Project No.:
Pages (hie. cover): 8 _ _ ~..,_
~~ Message: Grce Nettuno asked me to review the concerts you sent for the
~ ~ottndabout at Seminole Rd/Plaza/Sherry Dr. Attaclzod arc n~yy~reliminarv
.thou htrr, s. Plcasc reviewthem and advise me or Cncg,ifyou would like us to
nrocccd ~._~
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CONSULTANTS
GAI CONSCJi.TANTS ORIGINAL WILL:
618 East Soulh Strcct _ Follow via mail
Follow via overnight delivery
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Phone: (407)423-8398
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FAX: (407) 843-1070 contact us immediately, at (407) 423-$398,
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NOV-07-2003 FR I 04 ~ 26 PM GAI CONSULTANTS S. E, ..FAX N0. 4078431070 AGENDA tTEM asB
NOVEMBER 24, 2003
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CONSULTANTS
MEMORANDUM ~°~~
To: GREG NETTUNO
From: ~RASERHOWE
Subject: PROPOSED ROUNDABOUTAT SEMINOLE RD/PLAZA/SFiERRY DR, ATLANTIC BEACH
Date: 11l6/Z003
1 have reviewed the sketches from Bob Kosoy, Gity Director of Public Works, for the
subject intersection. I referred to .the .Florida Roundabout Guide (FRG), 2°d Edition
(FOOT, 5/98); .and Roundabouts: An Informational Guide (R1G), FHWA-RD-00-067,
these are the references we used to design the roundabout. for the City of Kissimmee's
MLK Blvd project. Please refer to the hand-drawn sketches :attached to the hard. copy of
this memo.
The geometry shown on the City's Apparent FRG Min
sketches generally conforms to'the FOOT Approach ___ Width Width
& FHWA guides, .using a 60-foot diameter NB Seminole Road 10' 19~~~
central island and 20-foot wide circulating NB Sherry Dr 10' 19'
roadway for asingle-lane roundabout. A WB plaza exit 12' 15'
few of the entry and exit lanes seem
narrow, but could be modified.
The major problem that I see with the layout is that the islands will not divert the path of
vehicles going. from Ns Sherry Dr to NB Seminole Rd; nor for those going west on Plaza
across the roundabout. To operate safely, the geometry of a roundabout must work to
slow down entering .vehicles to a speed close that of vehiclescirculating around the
central Island. This allows entering vehicles to merge into gaps between those already in
the roundabout;. and allows vehicles exiting Che roundabout to weave across. entering
traffic: This assumes that drivers obey the basic principle to yield to vehicles in the
roundabout..
The splitter islands on each approach force the driver to divert to the right at the yield
..line and the position of the central Island forces the driver to circulate with traffic. The
same thing happens to drivers exiting the roundabout -they must maneuver around the
central island, then around a fairly tight radius (30-foot min) to depart. I have sketched in
a few changes in the geometry to create diversions on the Sherry Dr and Plaza
apprdaches that may help this situation.
This effort to slowdown .vehicles (te about 20 - 30 MPH). also helps pedestrians
crossing the approach roadways. Note that the recommended geometry places the
splitter islands across. the crosswalks to give pedestrians a refuge to cross only dne '
direction of traffic at a time. This is a second problem with the conceptual layout -the
splitter islands between Sherry dr and Seminole Rd are not Irr line withthe obvious
pedestrian paths to cross those streets, i.e, people will probably cross before reaching
the islands.
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NOV-07-2003 FRI 04 27 PN GAI CONSULTANTS S, E, FAH N0. 4078431070. "
AGENDA ITEM #8B
NOVEMBER 24, 2003
The last issue 1 see is with several driveways fhat either enter. directly into the
roundabout or onto the approaches, very close to the roundabout. I understand that the
one into the roundabout is for a fire station; however I see 2 other drives entering
Seminole just south of the intersection. Could the fire station use these? Also, the drive
for #870 Seminole Rd is really too dose to the roundabout. Could they share a drivewith
#888 Seminole Rd or shift their drive to Plaza, west of the intersection?
I am most interested in supporting the City of Atlantic Beach to design in intersection
improvement here. The next step would be to do a Roundabout Just cation .Study, as
described in the PDOT Manual of Uniform Traffic Studies (NUTS), Form 750-020-18.
We would need the following information:
1. An accurate-topographiq survey (in CAD} of the intersection and approach
roadways.
2. 24-hour approach counts, peak hour turning movemen# counts and
pedestrian/bicycle counts, and transit routes.
3. Location of adjacent signalized intersections (to avoid causing problems there).
4. Location of nearby traffic generators and special uses (school, hospital, sports ar
entertainment facility).
The justification procedure will compare the operation of the roundabout to stop-sign and
traffic signal controls and estimate the average delay for vehicles using the intersectian.
If the City can provide. us with all of the data listed above, I estimate that we could
complete the report within about 32 hours of staff time. Please let know how you want to
proceed.
Attachments: 5
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.CONTENTS
spends to less than 20 kmPo (12 mph) neattho crossing. Pedesvian crossings -
across speeU tablos must Have detectable warning me[erlal as tlcscribedabove to
.clearly delineate [ho edge. oP the street. Speed tables should gonerally be ussd
.only on street with approach speeds of 55 km/h (35 mph) orless, as the in[rotluc-
tion of a raised speed table fn higher speed environments niay increase the likcli•
hood of singlc•vehicle crashes and is not consistent with thespeed consistency
philosophy presented in this document.
: 6.3.8 Splitter IS{ands - .
Splitter islands (also called separator islands or median isiands} should be provided. Spliteer islands perform
on all roundabouts, except those With very Small diameters at which the Splitter '. multiple functions and should
Island would obstruct ilia visibility of thecentral island.. Their purpOSe i5to provide generany be provided.
shelter For pedesvians (iricludinq wheelchairs.. bicycles,antl baby strollers), assts[
in controllingspeeds, guide vafhc inrothe roundabout, ptrysically separate enter-
ing and exiting tragic 5tfeamS, and dcrer wrong-way movemeltts. Additionally, Splitter
islanUS can bo used as a placo for mounting signs (see Chapter 7).
'the Splitter I„land envelope is formed by the entry and exit. curves on a leg, as
shown previously in Exhibits 644 and 6-25. The totatlength of the tsland should. .
generdlly be at leas[ 15 m {SOfq to provide sufficient protection for pedestrians and
to alert approaching drivers to the roundabout geomevy. ~dtlitionally, the Splitter
island should extend boyontl the end or the exit curve to prevent exiting VaFflc frbm
accidenLallyerossinginto the pathbP approaching traffic.
k:xhlbic ~-26shows the rninimum dimensions for a splftterisland at a single•
lane roundabout. including the location of the pedestrian crossing as discussed
in Section 6.3.7.
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DETAIL"A"
Roundabouts: An Informational Guitla s: GaomHric-0osign
E:hibit 6.26. Minimum
splidar Island dimensions.
NOV-07-2003 FR I -04 ~ 29 PM GAI CONSULTANTS S, E. FAX N0. 4078431070 AGENnA ITE1Vi #sB
NOV,yE~MBER 24; 2003
ra/
ttl 11VIHNMI(AVM1
,. CONTENTS
Exhibit BNi. Example of a
.typical singio~Iane roundabout
~gp I Faderal Highway Adm4liaq~uon