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Barry Ayotte
10056 Tayman Dr.
Union, Kentucky
(859) 372-4161
Mr. Anil Agrawal
1801 Alexander Bell Drive
Reston, VA 20191
Dear Mr. Agrawal:
Noted as one of the most functionally obsolete bridges by the ASCE, the Brent Spence Bridge case study compares the Brent Spence to other functionally obsolete bridges. The Brent Spence Bridge has not only concerned the people in the area that use the bridge but has also been noticed to be a major problem for the transportation departments working on this project for decades. Thus this report was made based on the concern of the Brent Spence Bridge’s safety and its purpose is to compare the necessity to renovate due to its overall lack in safety.
This report contains information on relevant to the Bridge Engineering journal concluding the link between bridges different levels of being functionally obsolete. I hope you find the relevancy of the case study to match the setting of your journal and decide to include it.
Sincerely,
Barry Ayotte
The Brent Spence Bridge Case Study
Prepared for Brandy Scalise
November 16, 2016
ii
Table of Contents
Introduction: Page 1
Problem: Page 3
Bridge Used for Comparison: Page 3
SR 520: Page 4
Brent Spence Bridge Problems Concerning Safety and Cost: Page 5
The Number of Commuters Effect on Safety: Page 6
Sight Distances and the Implications of Safety: Page 8
Lane Width and the Effect on Bridge Safety: Page 10
Cost of Renovations: Page 12
Conclusion: Page 13
References: Page 16
iii
Executive Summary
Purpose:
The purpose of this report is to identify and compare the necessity of
renovating the safety hazards on the Brent Spence Bridge to the cost it will
take to properly renovate these hazards. The safety hazards of the Brent
Spence must be assessed to prevent harm to the bridge’s users and the
costs it will encounter.
Research:
This report was mainly based off of research from the state’s department of
transportation for each bridge researched, scholarly articles about bridges
being functionally obsolete, and plans made for each renovation describing
the current state of each bridge and their current goals.
Key Findings:
There is sufficient evidence that the Brent Spence Bridge has unsafe
features (some that violate the FHWA for bridges) leading to the increased
chance of crashing while using the bridge. Also bridges defined as
functionally obsolete need to be identified further due to the lack of
information reported making it hard to categorize the levels at which being
functionally obsolete is dangerous.
Conclusion and Recommendation:
iv
The Brent Spence has been deemed to need renovations to improve safety,
there is a lack of information on bridges published, and the term
“functionally obsolete” needs to be further defined due to the large number
of bridges under this broad description.
1
Introduction
The case study of the Brent Spence Bridge plans to outline the details
of the bridge that undermine its safety and compare the details to the worth
in cost. Both the departments of transportation in charge of the bridge and
the citizens that know about the bridge, have known the existing functional
problems of the bridge for decades. Currently the Brent Spence Bridge is
not operating efficiently and costing lots of the bridges users’ lots of money
and time. Although many people are aware about the functionality of the
Brent Spence Bridge, there are misconceptions about what is truly the
problem. Therefore the Brent Spence Bridge was researched in depth to
find what the bridge is lacking in safety and can be fixed. The information
has been researched from various departments of transportation and online
documents listing the evidence of problems and their solutions. Thus this
information has been listed to address the safety attributes of the Brent
Spence Bridge.
To properly address the Brent Spence Bridges safety attributes the
area of discussion will be specific to the bridge’s state of functionality. The
functionality of the bridge has been chosen since the bridge has been
deemed structurally stable by the Ohio Department of Transportation.
Additional information also shows that the average bridge life is 50 to 100
years and the Brent Spence is just reaching the age gap, being built in
1963. Thus the issues with a functionally obsolete bridge are different than
2
those in a structural deficit bridge and need to be addressed separately. “A
‘functionally obsolete bridge’ has older design features and, while it is not
unsafe for all vehicles, it cannot safely accommodate current traffic
volumes, and vehicle sizes and weights, according to the American Society
of Civil Engineers” (McCarthy, 2007). Mostly the Brent Spence Bridge is
functionally obsolete due to the outdated design of the bridge. Currently it
has trouble accommodating the traffic on it and fails to meet other safety
regulations. In comparison, research sources show there are many other
bridges with the same title of being functionally obsolete. “More than three-
quarters of the 239 heavily used bridges in the nation’s capital are rated
structurally deficient or obsolete, the American Society of Civil Engineers
estimates” (Johnston, 2013). Because there are so many functionally
obsolete bridges, the Brent Spence is able to compare its features to other
bridges to evaluate its safety. But some bridges cannot be in direct relation
just because they are both labeled functionally obsolete since “[being
functionally obsolete] doesn't always mean they're unsafe, but neither does
it mean they're perfectly sound, and the amount of money needed to change
that is estimated in the hundreds of billions of dollars” (Eric, 2013). Thus to
decide whether the bridge can be compared, the same issues in safety and
cost have been taken into consideration for each comparison.
One of the main topics to discuss is comparing the safety is related to
cost. “The core problem still boils down to transportation funding. Just
before the I-5 bridge fell, the Seattle section of the American Society of Civil
3
Engineers estimated that Washington state had a $28.1 billion backlog of
bridge replacements and repairs” (Eric, 2013). Although the instance of the
I-5 bridge collapsing is not likely to happen to the Brent Spence this
example shows that the costs played a tremendous role in the upkeep of
safety. Thus the case study is also trying to evaluate what the cost has been
to replace safety hazards in relation to their importance. In an interview
with Dr. Erhardt he said that it all comes down to asking whether or not “is
it a good transportation system that will save money and promote the
welfare of the people who need it” (Dr. G, Erhardt, personal interview,
October 21, 2016). Thus safety and cost have been evaluated to answer this
exact question to determine whether renovations should be done on the
Brent Spence Bridge.
Problem
Currently the 3 major reasons that the Brent Spence Bridge is listed
as functionally obsolete. The current reasons are the number of vehicles
moving across the bridge has been over twice the amount it was designed
for, the lane width on the bridge is unsafe for the drivers, and the sight
distance are too short. As part of the case study of the Brent Spence Bridge,
these safety attributes will be in direct comparison to the other bridges that
are functionally obsolete. Also the cost for renovations based on projections
or actual costs will be included for evaluation. With this information one can
4
conclude whether the renovation on the Brent Spence Bridge promotes the
welfare for the people for a reasonable cost.
Bridge Used for Comparison
The bridge used below is used to study the effects of safety based on
the factors that make them functionally obsolete. The bridge is a river
bridge and has a speed of 50 mph when crossing. It is important to note
these conditions are most like the Brent Spence and can be compared
efficiently. Not all the bridges will have the same factors contributing to
their lack in functionality due to the information published has no checklist
to compare bridges functionality. Since not all bridges have been listed with
the same functionality problems and there is a lack of data on bridges, one
was selected based on its similarity to the Brent Spence Bridge. Although
they are different they are able to show why they are functionally obsolete
and can explain the reasons as to answer the question whether the
renovations are worth improving the safety for the cost.
SR 520 Bridge
The SR 520 Bridge has been developed to accommodate traffic across
Lake Washington. The bridge is a floating bridge and has been renovated
due to its design properties being functionally obsolete. The safety reasons
5
that have made this bridge functionally obsolete and in need of repair have
been due to the size of traffic reaching limits higher than the bridge was
designed for and little to no stretch of emergency lanes on the bridge
making it unsafe for drivers.
Research on the SR 520 Bridge has shown that most of its title of
being functionally obsolete comes from the abundance of traffic. “Originally
designed to carry 65,000 vehicles per day, the bridge currently serves an
average of approximately 100,000 vehicles per day” (Washington State
Department of Transportation). Operating at almost twice its design
capacity the average can be expected to be exceeded during peak hours and
can be imagined to be near failure in efficiency at these times. It has been
mentioned that there has been waiting on the bridge from an article on
World Access News which could mean that the level of service is very low
and could be ranked as either E or F. In the scenario that the SR 520 Bridge
operated at E or F levels of service, the bridge would be obsolete and near
failure or at failure in functionality. Thus the safety and lack of efficiency on
the bridge have proven to be major reasons in consideration for the
renovations on the bridge.
Secondly, the lack of emergency lanes was mentioned to be another
main source for renovations. The lack of safety lanes has been noted as a
violation of the FHWA for not having a total of 20 feet in emergency lanes.
The violation of the FHWA and implications of safety hazards were also
taken into consideration in the renovation plans. The importance in lane
6
width has shown its relevance while the importance and comparison is
further discussed when mentioned on the Brent Spence Bridge.
Currently, the research shows that the abundance of traffic and
insufficient lane width were the major reasons for renovations that costed
up to 4.56 billion dollars. Under this legislation budget they approved a new
floating bridge that included six lanes, emergency lanes, and a planned bike
lane. The research performed in the documents planning to build another
bridge to fix these safety issues only mentions these issues as there
reasoning for renovating. The Washington State Department of
Transportation’s website only goes in depth to include these reasons for the
functionality and not further describe their implications. Thus there is a lack
of information in correlating the effects of these safety hazards to the
potential improvement in welfare when the project finishes.
As an example of the lack of information, there is no mention of sight
distances to factor of safety when entering, on the bridge, and exiting. It is
only assumed that pictures of the bridge show that the surrounding area is
safe and open making sight distances optimal. Thus the exact data of the
bridge and the standards to compare are only evident when there is a
problem. Still, this shows the importance that the transportation
department values the efficiency of the bridge only based on the two safety
hazards it has mentioned.
7
Brent Spence Bridge Problems Concerning Safety and Cost
In this section the current information available on the functionality of
the Brent Spence Bridge will be described. Such topics include the
commuters of cars effect on safety, the lane widths effect on safety and the
stopping sight distances effect on safety. These are all measures of safety
that are related to other bridges and can be assessed. It its own category is
the cost of replacing the bridge. The cost of replacing the bridge can be
compared to other bridges choices to overcome their safety issues. Thus the
methods used by other bridges for renovations show the value of safety to
consider in what action would be best for the Brent Spence Bridge. By
discussing the safety factors and the comparable factor of cost to other
bridges that are functionally obsolete, a recommendation can be made as to
whether the safety is at such a great importance it is necessary to proceed
with renovations.
The Number of Commuters Effect on Safety
The Brent Spence Bridge has one of its largest safety problems routed
in the amount of traffic the bridge accommodates daily. Although other
components of the bridge also need to be improved to increase safety, the
sheer numbers and importance of the bridge cannot be reallocated due to
its very useful location. The current amount of vehicles used by the bridge
are 160,000 daily. This count of traffic for both direction exceeds the 80,000
8
vehicles that were designed to cross it daily. It has even been predicted that
the vehicles crossing the Brent Spence Bridge would reach 250,000 by
2040. From the data given the trend in the graph below projects rapid
growth from the time of the study (2013) till 2040.
Figure #1: Traffic Volume Predictions for the Brent Spence Bridge
It is important to address these statistics of traffic flow first in Figure
#1 because the public believe the amount of vehicles crossing the bridge
daily are making the bridge structurally unsafe. This belief can also be seen
from media sources portraying the bridge as structurally unsafe on several
accounts. There were only two main instances reported. One instance
happened when a concrete block fell from the bridge onto a car. Another
instance was when a truck became involved in a crash it broke through the
guard rail and fell off the bridge. Both incidents were addressed and the
Ohio Department of Transportation has reported that the bridge is still
1950 1960 1970 1980 1990 2000 2010 2020 2030 2040 20500
50
100
150
200
250
300
Traffic Volume Predictions for the Brent Spence Bridge
Year
Vehi
cles
Cro
ssin
g th
e Br
idge
(in th
ousa
nds o
f veh
icle
s dai
ly)
9
structurally sound after both accounts. Although the concrete slab falling
onto a car cannot be deemed as a result of the bridge being functionally
obsolete, the truck falling off the side of the bridge can. The reason it
occurred were the amounts of traffic left no room for the truck to stop so
instinctively the driver felt it necessary to avoid hitting the people in front
of them when unfortunately the guard rail failed. “Due to this increased
traffic flow, motorists are three to five times more likely to have a wreck
along this corridor than on any other portion of the interstate systems in
Ohio or Kentucky” (ODOT and KYTC, 2013). Most of the crashes reported
have been for the same reason of high traffic with no time to stop. Thus this
issue with safety on the Brent Spence Bridge has been linked to this factor
as a result in failure of bridge’s design.
In the Bridges design, the implementation of traffic the bridge is not
capable of handling makes the drivers more likely to crash. The statistic for
the likeliness to crash does pose a threat to daily commuters but it becomes
a greater risk considering the amount of trucks using the bridge. “It is also
one of the busiest trucking routes in the U.S., with freight equaling three
percent of the nation's gross domestic product (GDP) crossing the bridge
each year, according to a 2009 study from the Texas Transportation
Institute” (ODOT and KYTC, 2013).
10
Figure #2: Projected GDP That Crosses the Brent Spence Bridge
2009 2030
417
830
Projected GDP That Crosses the Brent Spence Bridge
Year of GDP
Gros
s Dom
estic
Pro
duct
(GDP
in b
illio
ns o
f dol
lars
)
Figure #2 above resembles the importance in the freight that crosses
the bridge years. The equivalent of the percentage of freight is about $419
billion. It has been predicted to almost double by 2030 according to the
study done in 2009. This statistic shows that the best method of travel for
businesses has been this bridge. The Brent Spence Bridge has been a
crucial route due to the roadways it is connected to. The shear amount of
trucks currently and prediction for that number trucks to increase make the
bridge become even more dangerous to use. In the past the safety due to
11
trucks was considered and a plan was attempted to make the bridge safer.
The attempt to make the bridge safer was ban so no truck could use the
bridge. The results of the ban showed that the trucks ended up taking
longer routes and only made other corridors susceptible to crashes. So to
make the bridge safer would require a change in the design. Therefore
renovations will be necessary for the bridge to accommodate the traffic it
has been receiving.
Sight Distances and the Implications of Safety
Currently one of the safety risks on the Brent Spence Bridge has been
the unsafe sight distances while crossing the bridge. The sight distances
that are unsafe include the traffic entering the bridge, the on-bridge traffic,
and the exiting traffic. Although there is no explicit explanation of where
there are violations of what the sight distances should be, there is evidence
linking the sight distances as a problem for drivers. In the research
performed no technical designs were found with the proper calculations
that would reveal what the sight distances should be to assure a drivers
safety. Thus without the information, more time would be needed to do the
in depth research needed. Although information was scarce, sight distances
are still a very important topic to discuss.
Considering the information on sight distances given in reports, the
entrance of a bridge proposes a bottleneck where traffic has to enter the
12
bridge. The sight distance was mentioned to be poor going up the entrance
ramp. On the bridge not only traffic, but the geometry of the bridge doesn’t
allow drivers to see the signs for exiting. Therefore if the drivers cannot see
what lane to be in to reach their exit, not enough time is given in making a
decision, which can lead to crashes. Sight distance is a factor in
determining sign placement given a formula with enough time to react.
Since not enough information is given as to the distance and time used in
the equation to determine the distances the signs were placed at, there is
no quantitative check. Sight distances were only mentioned as unsafe and a
concern mentioned in the documents considering a new bridge. Assuming
they did this calculation (as it would be necessary to place signs correctly)
they have proven it unsafe, otherwise the information is based on the
current experience and knowledge people have by crossing the bridge.
Using the calculation or making a new calculation, the current
method to move or fix the sight distances for exits couldn’t have been
performed. In an attempt to fix the sight distances, the ground on the
bridge has paved road signs in each lane as to where they lead to so people
can exit. These signs on the roadway have been noted to only help the
problem when the signs are still required for people to be able to see. Still,
when people exit the crowded bridge they frantically change lanes adding
to the increase in safety hazards. Overall the sight on the bridge is limited
and is one major concern considered in the process for renovating the Brent
Spence Bridge.
13
Lane Width and the Effect on Bridge Safety
Another factor of the road geometry that has been making the Brent
Spence Bridge unsafe is the lane widths. When the bridge was built it had 3
lanes of traffic for each tier of the double decker bridge. The increase in
traffic on the bridge soon demanded renovations. To accommodate the
demand the safety shoulders and 12 foot lanes were renovated. The
renovations made the lane widths 11 feet wide and completely removed the
shoulders so there would be 4 lanes on each tier of the bridge.
Currently these renovations make the bridge very unsafe and violate
FHWA standards. “Federal Highway Administration regulations require a
minimum of 12 feet in travel lanes and emergency lanes of at least 10 feet
on both sides of the travel lanes” (Strategic Advertisers LLC, 2013). The
purpose of lane width is for people driving at high speeds, such as the 55
mph speed of the bridge, would have more room in their lane to correct
themselves if they were close to leaving their lane. “On high-speed
roadways with narrow lanes that also have narrow shoulders, the risk of
severe lane-departure crashes increases” (FHWA, 2014). As of now the
smaller lanes and lack of an emergency lane show that the risk of lane
departure is at a maximum. The purpose of the emergency lane is for people
who need to stop or can be used in other ways if a crash occurs the high
density of traffic needs to be cleared for ambulances to reach the crash.
14
Both of the renovations to the width of the roadway and their implications
have demonstrated a lack of safety caused due to the increased risk driver
have in crashing.
To fix the current violations in safety the renovations recommended
by the Department of Transportation for both Kentucky and Ohio show how
lane widths and emergency shoulders have been an important role in
designing a new bridge. The consideration of building a new bridge is
proposed due to the renovations requiring more room for car on the bridge
that the structure currently cannot support. Since a new bridge has been
proposed, more lanes, lane widths, and sight distances can be address and
fixed properly. Two new bridge designs are shown below:
(“Designs I and I-A”, ODOT and KYTC, 2013)
The left image is the original design (I) while the right image show the
changes on the first proposal to save money (I-A). “On the proposed [I-A]
Brent Spence Bridge, outside shoulders were reduced from 14’ to 12’ and
inside shoulders were reduced from 14’ to 8’” (ODOT and KYTC, 2013). The
15
consideration of lane width and emergency lanes show increased
importance in lane width that currently proposed major issues on the Brent
Spence Bridge. But due to cost the bridge on the left, the right bridge was
recommended to still meet standards, but at a minimum. This shows that
with 6 lanes for each direction of traffic is the actual approximation needed
to handle the traffic the bridge accommodate today and traffic predicted
into the next 50 -100 years of the bridges life. Thus an increase of 4 lanes
total with the widths of the shoulder show an increase safety and the room
traffic on the bridge needs to function properly.
Cost of Renovations
Figure #3: Base Construction Costs
16
(“Initial base constructions”, ODOT and KYTC, 2013)
Since the I-A proposal is most likely to be accepted due to its qualifications
and lower price point it will be used in discussion to justify the cost. The
cost of the new Brent Spence Bridge in the figure below includes the price
including the amount it would take to install toll booths. This was included
to compare the price of the SR520 which has toll booths. There are many
variables that go into the price making it hard to compare where the exact
cost is going to in each bridge. The purpose of the cost is to show the
importance of functionally obsolete bridges. The main reasons the SR 520
required
Figure #4: Comparison of Bridges Costs
another bridge to be built was because of the current bridge couldn’t be
renovated to meet the current demands. The number associated with the
costs is to show the amount willing to be spend on a project to make these
fixes. Since the cost to renovate the Brent Spence Bridge falls under that
17
range and has a relatively normal cost for replacement compared to other
bridges, it is easily justified that the cost is reasonable for the safety issues
currently making the bridge unsafe. The increased welfare for the drivers
and the money saved in efficiency proves that the investment in a
renovations outweigh the cost it will be today.
Conclusion
During the research for the case study two conclusions were found.
The two conclusions were that the need to fix the Brent Spence Bridge is
apparent and outweighs the cost. The second conclusion is that there needs
to be more research or public information available to consider a better
ranking for functionally obsolete bridges. Using the information
provided in the report there is a clear importance to consider the levels at
which a bridge can be functionally obsolete. There is currently no standard
in defining the relativity in importance for functionally obsolete bridges.
Since an obsolete bridge can just mean a bridge isn’t operating as well as it
could there is an importance to make categories defining the significance
level while being functionally obsolete. Without this level of categorization,
research becomes difficult in finding bridges that are not only functionally
obsolete, but those that have safety issues and require attention to fix an
important problem. The Brent Spence Bridge happens to fall into a category
of bridges that require attention and would benefit greatly from
18
renovations. Not only is the evidence apparent that it would fall into a more
important category but there are many sources related to the need
providing methods to solve the problem.
Another issue that is relate to the need for categorization is the lack
of technical information to make a substantial comparison between the
different needs of bridges. Thus a second conclusion to be made is that
there must be a better system to obtain technical information on bridges
and a way to categorize their importance in pursuing renovations solely
based on the features that make them functionally obsolete. Two other
bridges considered in mentioning in the document were the Skagit Bridge
and the Frederik Douglass Memorial Bridge. Each bridge was listed as
functionally obsolete and had significant need for replacement, but lacked
enough data to mention in the report. Even on each bridge’s respective
department of transportation website, limited data was provided and was
less than the data mentioned in the Brent Spence Bridge and SR 520
documents. Even both Brent Spence and the SR 520 were still lacking in
sufficient data. To further analyze the safety in the functionality in bridges
would require more the exact plans for the bridge justifying their
measurements in safety based on traffic flow, roadway geometry, and other
safety factors. The information provided by the FHWA has been sufficient to
measure the bridges effective safety, yet the information about the bridges
themselves lacked the data to be compared. For example, the FHWA
mentioned the standards and levels of guard rails on a bridge yet no data
19
published for the Brent Spence Bridge mentions the type of guard rail used
on the bridge. Elements such as these have been left out and need to be
mentioned.
Overall the need for renovation is apparent on the Bren Spence
Bridge, but more information on the safety should be acquired to make
exact justifications for the relations between the specifications of the
problem and more detail about what can be done. Thus more data from the
actual design plans needs to either be published or sought out for a further
conclusion and a method to distinguish levels of functional obsolescence
should be developed to easily distinguish the vast amount of bridges safety
needs from others that fall under the too vastly described category of being
functionally obsolete.
20
References
Dr. Erhardt, G. (2016, October 21). Personal Interview.
FHWA. "Mitigation Strategies For Design Exceptions - Safety | Federal
Highway Administration." Mitigation Strategies For Design
Exceptions - Safety | Federal Highway Administration. FHWA, 15 Oct.
2104. Web. 06 Nov. 2016.
Jaffe, Eric. "Why America's Bridges Are in Such Dangerously Bad Shape."
Atlantic Cities (USA) 18 Jun. 2013, News. NewsBank. Web. 30 Oct.
2016.
Johnston, David Cay. "Pay to Fix America’s Crumbling Infrastructure Now,
or Pay More Later - The I-5 disaster in Seattle reflects the dire state of
our bridges and highways. But it may never be cheaper to replace
these aging arteries than it is now. By David Cay Johnston.." Daily
Beast, The 25 May 2013, News. NewsBank. Web. 30 Oct. 2016.
ODOT, and KYTC. "Options Analysis - Brent Spence Bridge Corridor." Brent
Spence Bridge Corridor. N.p., Sept. 2013. Web. 2 Nov. 2016.
McCarthy, Bill. "Could it happen here? - 3,025 - Total number of Wyoming
bridges 381 or 12.6 percent - Total structurally deficient bridges in
the state 230 or 7.6 percent - Total functionally obsolete bridges in
Wyoming 611 or 20.2 percent - Total deficient bridges in Wyoming
Source: U.S. Department of Transportation's National Bridge
21
Inventory database, December 2006." Wyoming Tribune-Eagle
(Cheyenne, WY) 3 Aug. 2007, Local News - Main: A1. NewsBank. Web.
30 Oct. 2016.
MoDOT. "I-70 Missouri River Bridge (Blanchette Bridge) Connecting St.
Charles and St. Louis Counties." Blanchette Bridge Renovations.
MoDOT, 2013. Web. 02 Nov. 2016.
"Safety." Build Our New Bridge Now. Strategic Advertisers LLC, 2013. Web.
06 Nov. 2016.
Washington State Department of Transportation. "SR 520 Bridge
Investment Grade Traffic and Revenue Study." Floating Bridge and
Eastside Project. Washington Department of Transportation, n.d. Web.
2 Nov. 2016.
Washington State Department of Transportation. "WSDOT - SR 520 Bridge
Replacement and HOV Program - Budget and Performance." WSDOT -
SR 520 Bridge Replacement and HOV Program - Budget and
Performance. Washington State Department of Transportation, 2016.
Web. 08 Nov. 2016.
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