Evaluations of Low Cost Safety Improvements Pooled Fund Study

PPT version for Printing

Oklahoma’s Experience with Wire 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 Oklahoma’Lake 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 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 Background

• 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	Picture 2	Picture 3

Brifen Wire Rope Safety Fence Features

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 Application

Center medians May be placed on either side of roadway

Basic 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 Benefits

• Economical Installation
  • Socketed Line Post System – Typical $15.95 LF
  • Driven Line Post System – Typical $ 12.00 LF
        (Installed Costs)
• Low 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
• High 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 Design
  • Visibility unobstructed through WRSF
  • Debris blows through Fence
  • Snow drift problem reduced
  • Drainage unaffected by Wire Rope Safety Fence

Brifen Wire Rope Safety Fence

Oklahoma City, OK – Lake Hefner Parkway

• 1000 Linear Feet Installation in September 2000
• 7 Mile Installation in July 2001

Picture 1

Picture 2	Picture 3

Brifen Wire Rope Safety Fence Lake Hefner Parkway Specifics

• 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—2001 to 2006

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

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

• Fatalities:

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

Brifen Wire Rope Safety Fence Lake Hefner Parkway Photos

Picture 1

Picture 2

Brifen Wire Rope Safety Fence Lake Hefner Parkway Impacts

Brifen Wire Rope Safety Fence
Lake Hefner Parkway Impacts

Northbound Impacts: 44 Posts: 200 Average: 4.54		Picture 1
Southbound Impacts: 97 Posts: 465 Average: 4.79		Picture 2

Brifen Wire Rope Safety Fence Lake Hefner Parkway

More Impacts

Picture 1

Picture 3 Picture 2

Brifen Wire Rope Safety Fence Lake Hefner Parkway

More Impacts

Picture 1

Picture 3 Picture 2

Brifen Wire Rope Safety Fence Typical Vehicle Damage

Picture 1 Picture 3

Picture 2

Picture 1	Picture 2
Picture 3	Picture 4

Brifen Wire Rope Safety Fence Socketed 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

Picture 1

Picture 2

Brifen Wire Rope Safety Fence Socketed Option – Easy Repair

Picture 1

Picture 2

• I–35 in Norman:
  • Prior to wire rope safety fence installation:
    • 7 fatalities, 39 injured (3 years)
    • Since installation (2005): NO fatalities, NO injuries. 140+ hits and several semi hits.
    • Installed in the center of the median; required a 6:1 slope or flatter; adjustments to the median drainage structures.

Picture 1

Picture 2

10 minutes, no re–tensioning

< Presentation 17 | Presentation 19 >