Item K05
BOARD OF COUNTY COMMISSIONERS
AGENDA ITEM SUMMARY
Meeting Date: March 21, 200 I
Division: BOCC
Bulk Item: Yes
No XX
Department: Comm. Nora Williams
AGENDA ITEM WORDING: Conceptual Approval of 18 Mile Stretch Compromise for enhanced two
lane highway that addresses safety concerns and increases ease of use in hurricane evacuation - also request for
specific concerns and questions regarding the specifics of the proposal currently under discussion.
ITEM BACKGROUND: The BOCC has expressed a commitment to keeping our evacuation clearance time
below 24 hours and has consistently opposed the addition of lanes on the 18 Mile Stretch.
PREVIOUS REVELANT BOCC ACTION: The BOCC has been revisiting hurricane evacuation issues
at every meeting since this subject reared its ugly head again last fall.
CONTRACT/AGREEMENT CHANGES:
STAFF RECOMMENDATIONS:
TOTAL COST:
BUDGETED: Yes
No XX
COST TO COUNTY:
REVENUE PRODUCING: Yes
No
AMOUNT PER MONTH_ Year
APPROVED BY: County Atty _ OMB/Purchasing _ Risk Management _
DIVISION DIRECTOR APPROVAL:
()~/lf( ~ [j)lfJl~j11r!J~:
(TYPE NAME HERE)
DOCUMENTATION:
Included XX To Follow_
Not Required_
DISPOSITION:
AGENDAITEM#J,~e)
Revised 2/27/01
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MEMORANDUM
MAR
7 2001
TO:
Hoard of County Commissioners
Monroe County
FROM:
David S. Kopp~l /V). ~
County Engineer {/J.l
DATE:
March 6, 2001
RE:
US I 18 Mile Stretch
Attached please find some information concerning median barriers - where they arc
warranted and how far they should be constructed from the travcllane. The use of a
median barrier should be considered only if striking the barrier is less severe than the
consequences that would result without the barrier. I think everyone agrees that the
barriers would improve safely in this instance. Figure 6.1 of the attached material further
indicates that a median barrier is warranted for the conditions that exist on the 18 mile
stretch.
However, when median barriers arc placed, they need to be located some distance from
the traveling vehicles. These barriers are like the concrete barriers you see on bridges.
For safety reasons, vehicles should be as far as possible from these small walls. So, what
is the proper distance? Rather than basing such a distance on the opinions of various
individuals, it would be best to follow established professional guidelines. The
publication, Roadside Design Guide published by the American Association of State
Highway and Transportation Officials (AASHTO) provides guidance in this area. In this
book, Table 5.3 indicates the recommended distance belween the travel lane and the
barrier. Based on a design speed of 65 mph, a lateral offset of nine feet is required.
(Please note that the design speed is a term that engineers use when designing roadway
plans and is not the speed limit). This distance helps errant motorists regain control of
the vehicle. Therefore, a minimum of nine feet should be used to separate the travel lane
from the median barrier.
1 am planning on being present at the March 21, 200 I ROCe meeting in the event that
this item comes up and you have questions for me.
DSK/jl
18MstretchUS 1 BOCC.DOC
cc: James L. Roberts
Dent Pierce
froM:
f'vbl':>h~.o
~ oaJ.&fJ.~
hI ~h<-
JJe:>'6" bviAe..
A",cr,u.I\ ^}>vc..,-"~Ol\
LAASHTO)
~ S+..-\<- HUh~)
'i- 'frQ^s/.,,.+....\H^ Ot'A.I..{)
CHAPTER 6: MEDIAN BARRIERS
6.0 OVERVIEW
A medIan barrier is a longitudinal barrier mosl com-
monly used to separate oppOsing traffic on a divided
highway. It is also used along heavily-travelled road-
ways to separate through traffic from local traffic or to
separate carpoollvanpool traffic from other highway
users. By definition, any longitudinal barrier placed
on the left side of a divided roadway may be consid-
ered a median barrier, but this chapter will address
only those that are symmetrical, i.e. designed to redi-
rect vehicles striking either side of the barrier.
This chapter references the performance require-
ments for median barriers, provides warrants for their
use, and contains guidelines for selecting and install-
ing an appropriate barrier system. The structural and
safety characteristics of selected median barriers, in-
cluding end treatments and transition sections, are
presented. Finally, seleclion and placement guide-
lines are included for new construction and methods
are presented for identifying and upgrading existing
substandard systems.
6.1 PERFORMANCE REQUIREMENTS
The performance requirements for median barriers
are identical to those for roadside barriers as dis-
cussed in Section 5.1. National Cooperative Highway
Research Program (NCHRP) Report No 230, "Rec-
ommended Procedures for the Safety Performance
Evaluation of Highway Appur lenances" contains de.
tailed information on the required series of full-scale
crash tests needed to evaluate the performance of
longitudinal barriers.
6.2 WARRANTS
As with all types of traffic barriers, a median barrier
should be installed only if striking the barrier is less
sevcre than the consequences that would result if no
barrier existed. Figure 6.1 suggests warrants for me-
dian barriers on high speed, controlled access road-
ways which have relatively flat, traversable medians.
These criteria are based on a limited analysis of me-
dian crossover accidents 1 and research studies2, and
are suggested for use in the absence of more current
(or site-specific) data. Barriers are typically consid-
ered for combinations of average daily traffic (ADT)
and median widths that fall within the dotted area. At
low ADT's, the frequency of median encroachments
is relatively low. Thus, for ADT's less than 20,000 and
median widths within the optional areas of Figure 6.1,
a barrier is warranted only if there has been a history
of cross-median accidents. Likewise, for relatively
wide medians, the probability of a vehicle crossing the
median is also low. Thus, for median widths greater
than 30 feet and within the optional area of the figure,
a barrier mayor may not be warranted, again depend-
ing on the cross-median accident history. Flat
medians that are wider than SO feet do not warrant a
barrier unless there is an adverse accident history. It
should be noted that after a warranted median barrier
is installed, accident severity may decrease, but acci-
dent frequency may increase since the space available
for return-to-the-road maneuvers is lessened.
Median barriers are sometimes used on high-vol-
ume, non-access controlled facilities. However, safely
terminating such barriers can be difficult and sight
distance may be a significant problem at intersections.
Spc(:ial consideration should be given to barrier
needs for medians separating roadways at different
elevations. The ability of an errant driver leaving the
higher roadway to return to the road or to stop dimin-
ishes as the difference in elevation increases. Thus,
the potential for cross-over accidents increases. For
such sections, the clear zone criterion given in Chap.
ter 3 should be used as a guideline for establishing
barrier need. Section 6.6.1.2 address the placement of
barrier on sloped medians.
The warranting criteria included in Figure 61 is
6-1
!!.l!.l!dsidt' Dl;sign G/!ide
_ Jr"w":;e~~ Shoulder. \fr~O;~'1-
~u_ Median Width_ __~
70
60
-
I--
w 50
lJJ
l1..
:r: 40
I--
9
?:
z 30
<(
a
w 20
:;E
10
00 20 40 GO 80
*Sased on a
5 year Projecti on
AVERAGE DAILY TRAFFIC*
(Thousand)
IB
~
Optional
Warranted
FIGURE 6.1
Median Barrier Warrants for Freeways and Expressways
relatively subjective and does not specifically address
the cost-effectiveness issue. Efforts are currently un.
derway to develop more sophisticated criteria using a
benefit to cost model that will address vehicle speed
and traffic mix as well as ADT and median slope and
width. The designer should keep informed of progress
in this area.
6-2
6.3 PERFORMANCE LEVEL
SEI~ECTION PROCEDURES
As with roadside barriers, most median barriers have
been developed, tested and installed with the inten-
tion of containing and redirecting pllssenger vehicles.
"noatliide Design G~ide
5.5.7 Aesthetic and Environmental
Considerations
Aesthetic concerns are not usually a significant factor
in the selection of a roadside barrier except in envi.
ronmentally sensitive locations such as recreational
areas or parks. In these instances, ariaturaHooking
barrier that blends with its surroundings is often se-
lected. In such cases, it is important that the systems
used be crashworthy as well as visually acceptable to
the highway agency.
Environmental factors may be important to con-
sider in the selection process. For example, barriers
with considerable frootage area may contribute to
drifting of sand or snow in some areas. Snow plow
operators should be cautioned against running the
blade next to the face of roadside barriers. Experi-
ence has shown that this practice will tear a metal rail,
and loosen mounting hardware and posts. Certain
types of railings may deteriorate rapidly in highly-
corrosive urban/industrial environments. In some
cases, solid barriers may restrict sight distances of
mOlorists entering the highway from a side road or
intersection, or may block a motorist's view of a par-
ticularly scenic panorama.
5.5.8 Field Experience
There is no substitute for documented proof of a
barrier's field performance. If a particular barrier
system is working satisfactorily and does not require
an extraordinary amount of maintenance, there is
liule reason to install a barrier for which these charac-
teristics are not conclusively known. If site conditions
warrant a non-standard instaUatioD, the highway
agency which developed and/or used the new system
should be contacted for specifIC information on the
system and on its performance.
It is particularly important that impact perfor-
mance and repair cost data be maintained by appro-
priate highway agency personnel and that the inf~r~
matian be made available to design and construction
engineers charged with selecting and installing traffic
barriers.
5.6 PLACEMENT
RECOMMENDATIONS
Having decided that a roadside barrier is warranted at
a given location and having selected the type of bar-
rier to be used, the design engineer must specify the
exact layout required. The major factors that must be
considered include the following:
5-28
· lateral offset from the edge of pavement
. terrain effects
. nare rate
. length of need
Most of these factors are interrelated to the extent
that the final design may be a compromise selected by
the designer. More detailed guidelines on each of
these factors are included in the next subsections.
5.6.1 Lateral Offset
As a general rule, a roadside barrier should be placed
as far from the traveled way as conditions permit.
Such placement gives an errant motorist the best
chance of regaining control of the vehicle without
having an accident. It also provides better sight dis-
tance, particularly at nearby intersections.
II is also generally desirable that there be uniform
clearance between traffic and roadside features such
as bridge railings, parapets, retaining walls and road-
side barriers, particularly in urban areas where there
is a preponderance of these elements_ Uniform align-
ment enhances highway safety by reducing driver re-
action and concerns. for those objects. The distance
from the edge of the travcled way, beyond which a
roadside object will not be perceived as hazardous
and result in a motorist's reducing speed or changing
vehicle position on the roadway, is called the shy line
offset. This distance varies for different design speeds
as indicated in Table 5.3. If possible, a roadside bar-
rier should be placed beyond the shy line offset, par-
ticularly for relatively short, isolated installations. For
long, continuous runs of railing, this offset distance is
not so critical, especially if the barrier is first intro-
duced beyond the shy line and gradually transitioned
nearer to the roadway. Uniform alignment also re-
duces the probability of vehicle snagging. However,
care must be exercised to insure proper transition
designs where a roadside barrier connects to one of
TABLE S.3 Suggested Shy Line Offset (L.) Values
Design Speed
(mph)
Shy Line Offset L.
(fect)
.
80
70r~S 11f>t\
60
50
40
30
12.0
q.()'~~:~
6.5
5.0
3.5
+ls
RESOLUTION FOR THE PROPOSED COMPROMISE SOLUTION FOR
THE 18 MILE STRETCH:
The Board of Monroe County Commission conceptually supports the
compromise solution of~n enhanced two lane highway with a median, the
northern bound side of which can be utilized as two northbound lanes only
in an emergency evacuation situation.
Possible Additions to the Conceptual Approval:
However, the BOCC of Monroe County has certain reservations about the
specifics of the current proposal that we would like addressed:
,'.
A) Although it is recogrirzed that the compromise must be significantly
wider than the existing highway because of the addition of shoulders and a
median, there is grave discomfort that the entire width of concrete could
eventually allow for the removal of that median, the addition of asphalt to
the shoulders and the striping of a highway with three, even four lanes. For
reassurance on this compromise now and into the future, the BOCC would
like to request an agreement between FDOT, the Governor and the BOCC
that this compromise cannot be changed or reconfigured to result in more
than two non-emergency lanes without the entire process of project review
and approval starting over.
B) The BOCC questions whether the width of the bridge and the presence of
the median on the bridge is necessary. There is not a single bridge with such
a median within the County. While we support the median on the 18 Mile
Stretch that emerges from the northern side of the bridge, we would ask for
reconsideration of the use of the median on the bridge itself.
C) The proposed compromise, while 1/10th the width of the originally
proposed four-lane highway, it still 58' wide and causes some concern,
especially among our northern-most residents. We would ask, before we can
support this width, that you provide us information on any highway within
the State of Florida where such a median exiSts for a distance of greater than
one mile, with a smaller inside shoulder adjacent to it - as well as an
explanation of why we should not support that alternative distance on the 18
Mile Stretch Compromise.
\.//-"
-r-;>
COPY OF EMAIL CONCERNING THE 18 MILE STRETCH COMPROMISE SENT
BY DCA'S STEVE SEIBERT TO DAVID RITZ, OCEAN REEF:
-----Original Message-----
From: Steve Seibert [mailto:Steve.Seibert@dca.state.fl.us]
Sent: Friday, March 16,2001 5:33 PM
To: dritz@orcareefcom
Subject: Florida Keys Hurricane Study
Dear Mr. Ritz:
Some time back, Governor Bush forwarded your email to me, asking me to
respond. I apologize for the delay in getting an answer to you. As you
might guess, both the Governor and I have received quite a number of letters
and emails on this subject.
It is our opinion that ensuring the safety of residents and visitors in the
event of a hurricane is one of the state's most important responsibilities
in the Florida Keys. For that reason, the Governor directed the Department
of Transportation to conduct a study to determine how long evacuation from
the Keys would take. Although the final version of the study is not
complete, we know enough at this point to say the clearance time standard of
24 hours established by the Governor and Cabinet in 1996 has been exceeded
in Category 3 and higher storms. The study is also supposed to identify
improvements to the evacuation network to shorten clearance times. The
18-mile stretch is an integral part of that network. Originally, the study
recommended improvements which would result in one lane into Key Largo and
two lanes out. Because of the significant concerns that have been raised
regarding this option, an alternative approach is being appraised which
involves one lane in, a fixed median barrier, and one lane out, with an
expanded shoulder which can be converted to an evacuation lane when needed.
The Jewfish Creek Bridge would be rebuilt and widened to accommodate this
road configuration.
Once the appraisal of this alternative is complete, local government and the
public will again be asked for input before the final program of
improvements is adopted. Public involvement is a very important part of
this process and we appreciate your letting us know your views. If you have
any questions about the project, please call either Mike McDaniel at (850)
487-4545, or Frank Koutnik at (850) 413-9969. Both gentlemen are on my
staff.
Very truly yours,
Steven M. Seibert
Secretary, Department of Community Affairs