oklahoma’s experience with wire rope safety fence

Oklahoma’s Experience with Oklahoma’s Experience with Wire Rope Safety FenceWire Rope Safety Fence

• In Oklahoma, median crossover accidents have increased.

• State Under Pressure

• In response to the increase in median crossover accidents, in 2006 ODOT initiated a program to install wire rope safety fence at critical locations through out Oklahoma.

First Installation in OklahomaFirst Installation in OklahomaLake Hefner ParkwayLake Hefner Parkway

Opened in 1991 6 lane divided highway approximately

44’ grass median; no highway lighting 108,000 ADT (2000) Speed limit 65 mph Site of 185 Crossover accidents – 6

Fatal, 77 injured from June 1, 1997 through May 31, 2001

Lake Hefner ParkwayLake Hefner Parkway Considered three options: concrete median

barrier, strong-post guardrail and cable barriers. Cost/mile for each option: Concrete median barrier: $500,000 Double-face W-beam guardrail: $105,000 Wire Rope Safety Fence-Socketed system:

$84,000 Selected the Brifen wire rope safety fence with

socketed system.

Brifen Wire Rope Safety Fence Brifen Wire Rope Safety Fence BackgroundBackground

• Developed by Brifen Ltd. in the United Kingdom in 1989

• In use in over 30 countries and 1/2 of the states

• NCHRP-350 TL3 approved by FHWA in March 2001

• Licensed Brifen USA, Inc. in November 2002 Picture 1

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Brifen Wire Rope Safety Fence Brifen Wire Rope Safety Fence FeaturesFeatures

• 10’-6” (3.2 m) Post Spacing

• Four Rope High Tensioned System

• Aesthetically Appealing

• Minimal Deflection

• Socketed System – Easy to Repair

• Capable of Long Segment Length Between Anchors

• Proven Crash Testing and Real World Experience

Brifen Wire Rope Safety Fence Brifen Wire Rope Safety Fence ApplicationApplication

• Center medians

• May be placed on either side of roadway

Basic Design CriteriaBasic Design Criteria• Recommend slopes of 6:1 or flatter

• Predictability of vehicle at impact with WRSF at normal height with all wheels still on ground

• Deflection less than 8 feet

• End anchors can be miles apart

Brifen Wire Rope Safety Fence Brifen Wire Rope Safety Fence BenefitsBenefits

• Economical InstallationEconomical Installation• Socketed Line Post System – Typical $15.95 LF

• Driven Line Post System – Typical $ 12.00 LF

(Installed Costs)

• Low Occupant Ridedown AccelerationLow Occupant Ridedown Acceleration• NCHRP-350 TL3 Maximum - 20 G’s

• Brifen 898 kg Car - 4.0 G’s

• Brifen 2000 kg Pickup - 2.86 G’s

Brifen Wire Rope Safety Fence Brifen Wire Rope Safety Fence Benefits Benefits (Continued)(Continued)

• High Tensioned Prestressed RopesHigh Tensioned Prestressed Ropes• Reduced dynamic deflection

• Reduced length of barrier damaged in crash

• Secondary hits successful between repairs

• Low maintenance costs

• Wire Rope Safety Fence Open DesignWire Rope Safety Fence Open Design• Visibility unobstructed through WRSF

• Debris blows through Fence

• Snow drift problem reduced

• Drainage unaffected by Wire Rope Safety Fence

Brifen Wire Rope Safety Brifen Wire Rope Safety Fence Fence

Oklahoma City, OK - Lake Hefner ParkwayOklahoma City, OK - Lake Hefner Parkway• 1000 Linear Feet Installation in September 2000

• 7 Mile Installation in July 2001

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Brifen Wire Rope Safety FenceBrifen Wire Rope Safety Fence

Lake Hefner Parkway Lake Hefner Parkway SpecificsSpecifics

• Wire Rope Safety Fence installed in median 2 feet from existing southbound shoulder

• Asphalt widening under WRSF for weed barrier

• Seven miles in length

Accident History—Accident History—2001 to 20062001 to 2006

•Since 2001, over 430 hits. In 2/3 of those Since 2001, over 430 hits. In 2/3 of those hits, driver kept going.hits, driver kept going.

• Injuries:Injuries:

Reduced from 77 injuries in 2001 to 8 Reduced from 77 injuries in 2001 to 8 injuries in 2006.injuries in 2006.

• Fatalities:Fatalities:

Reduced from 6 fatalities in 2001 to 1 fatality in 2006.

Brifen Wire Rope Safety FenceBrifen Wire Rope Safety Fence Lake Hefner Parkway Lake Hefner Parkway

PhotosPhotos

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August 1, 2001 To December 1, 2002August 1, 2001 To December 1, 2002

Total Impacts: 141Total Posts: 665Avg Posts/Impact: 4.71

Brifen Wire Rope Safety FenceBrifen Wire Rope Safety FenceLake Hefner Parkway Lake Hefner Parkway

ImpactsImpacts

Brifen Wire Rope Safety FenceBrifen Wire Rope Safety FenceLake Hefner Parkway Lake Hefner Parkway

ImpactsImpactsAugust 1, 2001 To December 1, 2002August 1, 2001 To December 1, 2002

Northbound Impacts: 44 Posts: 200 Average: 4.54

Southbound Impacts: 97 Posts: 465 Average: 4.79

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Brifen Wire Rope Safety FenceBrifen Wire Rope Safety FenceLake Hefner ParkwayLake Hefner Parkway

More ImpactsMore Impacts Picture 3Picture

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Brifen Wire Rope Safety FenceBrifen Wire Rope Safety FenceLake Hefner ParkwayLake Hefner Parkway

More ImpactsMore Impacts Picture 1

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Brifen Wire Rope Safety FenceBrifen Wire Rope Safety FenceTypical Vehicle DamageTypical Vehicle Damage

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Brifen Wire Rope Safety FenceBrifen Wire Rope Safety FenceTypical Vehicle Damage Typical Vehicle Damage

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Brifen Wire Rope Safety FenceBrifen Wire Rope Safety FenceSocketed SystemSocketed System

• Typical repair time under 30 minutes

• Only one person required

• No specialized tools (except tension meter on occasion)

• No lane closures required for heavy equipment

• Inexpensive – normally just a few posts

• There has been no damage to ropes or rigging screws in over 430+ impacts

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Brifen Wire Rope Safety FenceBrifen Wire Rope Safety FenceSocketed Option – Easy Socketed Option – Easy

RepairRepair

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I-35 in Norman:I-35 in Norman: Prior to wire rope safety fence Prior to wire rope safety fence

installation:installation: 7 fatalities, 39 injured (3 years)7 fatalities, 39 injured (3 years) Since installation (2005): NO fatalities, NO Since installation (2005): NO fatalities, NO

injuries. 140+ hits and several semi hits.injuries. 140+ hits and several semi hits. Installed in the center of the median; Installed in the center of the median;

required a 6:1 slope or flatter; adjustments required a 6:1 slope or flatter; adjustments to the median drainage structures.to the median drainage structures.

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10 minutes, no re-tensioning10 minutes, no re-tensioning