Brent Spence BridgeKentucky – Ohio Safety Team

Team Members:E. Thomas Arnold, Jr., P.E. (ODOT)

Tammy Campbell, P.E. (ODOT)

Corrin Gulick, P.E. (KYTC)

Jay Hamilton, P.E. (ODOT)

James Minckley, P.E. (KYTC)

Brandon Seiter, P.E. (KYTC)

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Introduction

The Brent Spence Bridge is a major interstate bridge along the interstate 71/75 corridor that connects Kentucky and Ohio. The bridge has two decks. The upper deck carries southbound traffic, and the lower deck carries northbound traffic. Each deck is four lanes wide. The existing high traffic volume, narrow shoulders, narrow lane width, and other design deficiencies contribute to the accident history on the bridge. There is currently a major design project to correct some of the substandard issues on the bridge. However, budget shortfalls may delay the project.

Due to the high accident rate on the bridge, the Kentucky Transportation Cabinet (KYTC) and the Ohio Department of Transportation (ODOT) have created a multi-disciplinary team to analyze the various issues contributing to accidents on the bridge. The team used existing accident, speed, and volume data to determine feasible countermeasures with relatively low environmental and fiscal impacts. The countermeasures discussed in this report are recommended in order to reduce accidents before the reconstruction project can be funded.

Crash Analysis

Accidents on the Brent Spence Bridge were studied for a three (3) year period. This included the dates from August 1, 2008 to August 1, 2011. This accident analysis yielded the following results:

Northbound Southbound TotalTotal Collisions 49 94 143

Rear End 27 45 72Rear End Injuries 10 14 24

Rear End Fatalities 0 1 1Sideswipe 17 45 62

Sideswipe Injuries 2 5 7Sideswipe Fatalities 0 0 0

Single Vehicle 5 4 9Single Vehicle Injuries 0 1 1

Single Vehicle Fatalities 0 0 0

Table 1 - Accidents on the Brent Spence Bridge from 8-1-2008 to 8-1-2011

Table 1 shows rear-end collisions are the most frequent type of crash on the bridge. Rear-end collisions account for 75% of the injury collisions and the only fatality on the bridge in the past three years.

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Crash Rates

The ADT of the Brent Spence Bridge in 2009 was 167,386 vehicles per day (vpd). Nearby traffic stations show an approximate directional split of 50/50. Therefore, each deck of the Brent Spence Bridge carries approximately 83,693 vpd.

Using the data from Table 1 and the ADT on the Brent Spence Bridge, crash rates were calculated for northbound, southbound and both directions. Note that the Kentucky crash rates were converted in order to create a more accurate comparison to Ohio crash rates. This data is shown in Table 2.

Table 2 –Crash Rates for the Brent Spence Bridge (BSB) in Crashes/Million Vehicles/Mile

The data in Table 2 shows that the crash rates for both north and southbound I-71/75 on bridge is higher than the average crash rate for urban interstates in both Ohio and Kentucky. Table 2 also shows that accidents in the southbound direction are nearly twice that of the northbound direction. Southbound crash rates are almost five times the crash rate in Ohio and 3.5 times the crash rate in Kentucky on similar roadways. As a result, the bridge is classified as a location with a high probability of collisions for both states.

1.78

3.42

2.6

0.97 0.97 0.97

0.69 0.69 0.69

0

0.5

1

1.5

2

2.5

3

3.5

4

Northbound Southbound Both Directions

Comparison of BSB Crash Rates with KY and OH Average Interstate Crash Rates (2008-2010)

BSB Crash Rates Average KY Interstate Crash Rate Average OH Interstate Crash Rate

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Speed Analysis

A travel speed study was conducted for the Brent Spence Bridge. The study measured average travel speeds in the AM and PM peak hours for both the northbound and southbound directions. The table below shows the average speeds on the bridge:

Direction and Peak Time

Average Speed

Northbound AM 34.5Southbound AM 56.2Northbound PM 35.3Southbound PM 38.1

Table 3 – Average Speeds for AM and PM Peak Hours on the Brent Spence Bridge for Northbound and Southbound Traffic.

As shown in Table 3, the average travel speeds do not exceed 40 mph for northbound traffic in the AM or PM peak or for southbound traffic in the PM peak. However, the southbound average travel speeds exceed the 55 mph speed limit during the AM peak. It can be concluded from this table that southbound traffic on the bridge is typically faster than northbound traffic on the bridge.

Countermeasure Analysis

The team discussed the crash and speed data, and then the team collected additional data from a field review. Based on all of the information, specific issues were discussed, and countermeasures of each issue were evaluated by the team. Due to budget constraints, countermeasures that require geometric improvements are not discussed in this report.

v Issue 1 – Weaving Vehicles (Northbound and Southbound)

The data shows that the weaving maneuvers associated with the 4th and 5th Street ramps on and off of I-75 contribute to sideswipe and rear-end collisions. Anytime a vehicle changes lanes, potential points of impact are created, increasing the probability of a collision.

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Northbound:

Figure 1 – Configuration of Exits north of the Brent Spence Bridge

The existing lane configuration on the northbound portion of the bridge creates weaving condition. As shown in Figure 1, I-71 and I-75 split just north of the bridge. Also, the Covington 4th Street ramp onto the bridge adds a lane to the right side of the interstate on the south side of the bridge. Depending on the desired exit, a vehicle could change lanes up to three times on the bridge. This condition contributes to sideswipe and rear-end collisions.

Furthermore, the substandard vertical clearance on the northbound deck obstructs sight distance to the overhead directional signage. Until May 2011, the obscured panel signs were the only indication to drivers of the correct lane position. However, a project to place pavement tattoos was completed May 12, 2011. Pavement tattoos are thermoplastic lane markings that indicate the correct lane placement for nearby exits. Both KYTC and ODOT have received positive feedback on the installation of the pavement markings. The pavement tattoos are shown in Figures 2 through 4.

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Figure 2 – Pavement Tattoos on the Northbound deck of the Brent SpenceBridge

Figure 3 – Pavement Tattoos on the Northbound deck of the Brent Spence Bridge

Figure 4 – Pavement Tattoos on the Northbound deck of the Brent Spence Bridge.

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Southbound:

Weaving maneuvers in the southbound direction are also an issue. Vehicles entering I-75 from I-71 must cross up to three lanes of traffic in order to take the 5th Street exit, on the Kentucky (south) end of the bridge. This condition combined with the higher speed in the southbound direction contributes to rear end and sideswipe accidents on the southbound deck.

Figure 5 – Southbound Brent Spence Bridge. I-71/75 remains four lanes past the bridge.

Countermeasure 1A – Close the 4th/5th Street Ramps On/Off I-75

Closing one or both of the 4th/5th street ramps in Covington would eliminate the need for vehicles entering or exiting Covington from I-75 to cross multiple lanes of traffic on the bridge. Furthermore, capacity of I-75 would be increased by eliminating access points. This countermeasure would likelyreduce rear-end and sideswipe accidents.

Although closing the ramps would reduce accidents, it would also have significant impacts beyond the scope of this report. Vehicles currently using the 4th and 5th Street ramps would be forced south to the 12th Street exit. This exit may not have the capacity to handle the additional trafficin the existing configuration. Also, the existing traffic patterns in Covington would be impacted. Mitigation of these impacts is not feasible for this project, and this countermeasure is not recommended by the team.

Cost = N/A

Recommended = No

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Countermeasure 1B – Additional Signage and Striping Northbound

The added lane on northbound I-75 from the 4th Street ramp is separated from the right-most lane on I-75 by white skips just past the gore. During the field review, the team noticed that the white skips were almost completely worn off of the pavement, for a distance approximately 300 feet past the gore. This can create the illusion that there is a merge condition at the end of the ramp, rather than an added lane. The faded skips increase the confusion in the weaving area.

The added lane could be better delineated by adding an Added Lane (W4-3) sign and an 8 inch white channelizing line from the gore that extends approximately 300 feet north. The channelizing line couldresist fading from vehicular wear better than standard skips. This countermeasure would likely reduce rear-end and sideswipe accidents. Figure 6 shows an example of the proposed sign.

Figure 6 – Entering Roadway/Added Lane (W4-6) Sign

Cost:Sign = $200Stripe = $500

Recommended = Yes

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Countermeasure 1C – Additional Signage Southbound

Vehicles traveling from I-71 onto southbound I-75/71 may not have sufficient time to process the sign for the 5th Street exit on the Kentucky (south) of the bridge. The next visible sign is located at the exit. There is not sufficient time to change lanes safely, if the first sign is missed. This condition contributes to the weaving issue on the southbound portion of the bridge and increases the probability of rear-end and sideswipe crashes.

A new truss and panel sign on the interstate would cost approximately $75,000. It is not anticipated that enough collisions would be reduced to justify the cost of the sign. Furthermore, it may not be feasible to install a sign at this location without structural modifications to the bridge. Therefore, this countermeasure is not recommended.

Although a panel sign would not be cost effective, dual mounted smaller signs would cost about $200per sign. This would be a more cost effective safety measure. The small sign could say “5th St Next Right” and be strapped to the right and left side of the bridge. The sign would likely reduce rear end and sideswipe accidents without structural modifications. If crash trends persist, evaluation of additional delineation such as pavement tattoos can be evaluated.

Figure 7 – Southbound Brent Spence Bridge, showing a possible location foradditional directional dual mounted signs

Cost:Panel Sign = $75,000Small Directional Sign = $400

Recommended:Panel Sign = NoSmall Directional Sign = Yes

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v Issue 2 – Slowing Vehicles on the Bridge

Rear-end accidents is the most common and severe type of collision on the bridge. Sudden changes in driver speed and driver inattention can contribute to rear-end collisions, especially on a high speed facility such as I-71/75. Accident reports indicate that unprepared drivers are colliding with slowed or stopped vehicles, resulting in a rear-end collisions on the bridge. Rear-end collisions contributed to 50% of the total accidents, caused of 75% of the total injuries, and are responsible for the one fatality on the bridge in the past three years.

Countermeasure 2A – Additional ARTIMIS Camera

The Advanced Regional Traffic Interactive Management and Information System (ARTIMIS) provides accident and congestion information to motorists in the Cincinnati/Northern Kentucky area, including the Brent Spence Bridge. ARTIMIS is a web-based tool that helps identify areas that requires drivers to slow down.

The existing ARTIMIS system does not adequately cover the bridge. Adding additional coverage to the bridge would help bring awareness to drivers of potential slowing vehicles or other dangerous conditions on the bridge. The camera would also help improve emergency response time on the bridge. Due to the curvature of the bridge, the team recommends installing four additional cameras to provide adequate coverage. This countermeasure would likely reduce rear-end collisions on the bridge.

The cost estimate for this countermeasure relies on existing conditions in the field, such as the availability of power and communications. For the purpose of this report, $11,000 was assumed per camera. However, this price and the feasibility of additional cameras for the bridge could change as field conditions are further evaluated.

Cost = $44,000

Recommended = Yes

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Countermeasure 2B – “Watch for Stopped Traffic” Sign

Bringing attention to unexpected traffic conditions can increase driver awareness and reduce accidents on the bridge. Stopping on an interstate bridge is not always an expected maneuver. The team discussed installing a warning sign that says “Watch for Stopped Traffic.” This sign would warn motorists that there may be a condition on the bridge that requires them to stop, and likely reduce rear end accidents. However, the team is concerned the sign would lose effectiveness over time.

Figure 8 – Example of “Watch for Stopped Traffic” warning sign

Cost = $400

Recommended = Yes

Countermeasure 2C – LED “Watch for Stopped Traffic” Sign with Speed Sensors

If there is not always stopped traffic on the bridge, the sign can become less effective over time. Motorists that pass a warning sign that does not reflect accurate conditions 100% of the time, typically disregard the sign as they pass the sign more frequently.

The team considered this, and discussed a possible solution to maintain theintegrity of the sign. Solar powered signs are available with flashing LED lights around the boarder. The LED lights could be connected to speed sensors on the bridge. The speed sensors would also be placed on the bridge in each direction, so they can detect northbound and southbound speeds. If the speed of vehicles on the bridge dropped, the LED lights on the sign would be triggered and the sign would flash. The sign would not flash if the speed sensors did not detect slowing or stopping traffic. This design would have more impact on drivers than the standard warning sign, and likely reduce rear end accidents. Should crash patterns persist, a more dynamic message sign could be considered.

Cost = $12,000

Recommended = Yes

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Conclusion

The purpose of the Brent Spence Safety Review is to determine feasible safety improvements that can be implemented prior to the Brent Spence Bridge reconstruction project. Geometric modifications to the bridge were considered outside the scope of the review.

The team used collision, volume, and speed data to analyze different issues on the Brent Spence Bridge. The data shows that the southbound portion of the bridge has a higher collision rate, and vehicles travel at higher speeds. However, both southbound and northbound portions of the bridge have accident rates that exceed the average collision rates of urban interstates in Ohio and Kentucky.

Two major issues were identified as contributing factors to the higher than average crash rate on the bridge. These issues included weaving maneuvers and slow or stopped traffic.

Several countermeasures were evaluated to address these countermeasures, and reduce accidents on the bridge. Some countermeasures were not recommended, such as closing the 4th/5th Street ramps in Covington or installing an additional panel sign on the bridge. However, the team did recommend the following countermeasures:

• Install a 300 foot 8 inch white channelizing line at the added lane on the northbound portion of the bridge near the 4th Street ramp onto I-75 in Kentucky.

• Added Lane (W4-3) sign on the northbound portion of the bridge near the 4th Street ramp onto I-75 in Kentucky.

• Add an additional sign on the southbound portion of the bridge stating, “5th Street Next Right.”

• Add an additional ARTIMIS camera for the southbound portion of the bridge.

• Add a “Watch for Stopped Traffic” sign for Northbound and Southbound traffic.

• Add a “Watch for Stopped Traffic” Sign for Northbound and Southbound traffic with a flashing LED strip of lights around the perimeter of the sign. Add speed sensors on the bridge that triggers the sign to flash when speeds drop significantly.

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Of the recommendations, there are two alternates for the “Watch for Stopped Traffic Signs.” One includes flashing LED lights, and the other is a more standard design. The table below shows an estimate that incorporates each version of the sign.

ITEM NUMBER

ITEM DESCRIPTION QUANTITY UNITTOTAL COST

PER ITEM

1 Added Lane Sign (W4-3) 1 EA $200.002 8 Inch White Strip 300 LF $500.00

3Custom Directional Sign "5th

Street Next Right"1 EA $400.00

4 ARTIMIS Camera 4 EA $44,000.005 Traffic Control 1 LS $65,000.006 Contingency 15% total cost

7"Watch for Stopped Traffic"

Warning Sign2 EA $400.00

8

LED Flashing "Watch for Stopped Traffic" Warning Sign System With Speed

Sensors

2 EA $ 12,000.00

Total A (Items 1-7) $126,600.00Total B (Items 1-6 and 8) $140,400.00

Table 4 – Cost Estimate of Proposed Countermeasures

The countermeasures described in this report will likely reduce accidents on the Brent Spence Bridge without major changes to the existing geometry. However, the geometric deficiencies on the bridge contribute significantly to the high accident rate. Major substandard geometry on the bridge includesthe ramps, the vertical clearance of the northbound deck, and the absence of shoulders on the entire bridge. Although the countermeasures mentioned in this report will reduce accidents, the geometric issues must be addressed in the Brent Spence Bridge reconstruction project, in order for crash rates to reach an acceptable level.