High Tension Cable Median Barrier March 17, 2011

Cross median crashes Cross median crashes are 3 times more deadly than other types of crashes. A vehicle travelling at highway speeds can cross a 36 to 50 median into oncoming traffic in the time it takes to: –Change the radio station –Answer a cell phone –Yawn

Cross Median Crashes Difficult to solve –No specific time of day, week, month or year –Take place on vertical and horizontal curves as well as straight and flat sections of roadway –Various causes Fatigue Improper lane changes Inattention Medical Emergencies

Patterns Emerging Entrance and exit ramps that lead to weaving maneuvers Changes in the number of lanes Median cross sections

Good News Research has shown that protective barrier can prevent most cross median crashes, regardless of the circumstances. Goal of Cable median barrier: Contain vehicles in the median once they leave the roadway where they are less likely to involve other vehicles and cause a multi-vehicle crash.

Definition Cable median barrier is 3 or 4 steel cables, tensioned and strung on posts. Office of Traffic, Safety and Technology

Benefits of Cable Median Barrier Most versatile and forgiving barrier system available for reducing the severity of run-off-road crashes. –When struck Posts break Cables flex Absorbs most of the crashs kinetic energy Redirects the vehicle along the barrier National studies have shown a 96% reduction in fatal cross median crashes. Office of Traffic, Safety and Technology

Benefits of Cable Median Barrier Can be installed on a slope 4:1 or flatter Farther away from the traveling public Show a substantial reduction in fatal and injury crashes when compared to concrete and metal beam barriers Low installation costs Office of Traffic, Safety and Technology

Minnesota Examples Office of Traffic, Safety and Technology Video 1

Multiple Hits Office of Traffic, Safety and Technology Video 2

Placement in Median Major factors to consider are: FHWA and NCAC (National Crash Analysis Center) guidance Median configuration (slopes, width, depths, etc) Future adjacent roadway projects Maintenance Office of Traffic, Safety and Technology

FHWA Approval Letters o V- ditches o Approved 0- 4 down the 1:4 fore slope with >9-10 from the ditch bottom Most of our median ditches are : o Trapezoidal ditches o 1:4 foreslope o Average depth of 2 FHWA and NCAC Guidance

National Crash Analysis Center (NCAC) Modeling and Simulation Over 80 modeling and simulations were completed

Median Placement Criteria Direction of majority of lane departures o Place cable on opposite side of median Computer models o Place as far from the travelling public as possible o Keep within 6 feet of top of side slope Avoid the middle of the median o Soil Conditions o Maintenance

Placement In Median Office of Traffic, Safety and Technology Video 3

Cable Median Installations Minnesota Data 260 miles installed to date % Reduction in target K&As Additional 90 miles planned

Study Details MNs first 75 miles installed 2004, 2005, 2006 and fatal crashes in the 3 years prior to installation 13 fatalities were target crashes Run off road left Head on Sideswipe opposing 0.75 miles were excluded from the study because of inaccurate reference points Office of Traffic, Safety and Technology

Study Results Office of Traffic, Safety and Technology

Crash Costs Fatality (K) = $7,100,000 Incapacitating (A) = $415,000 Nonincapacitating (B) = $137,000 Possible (C) = $91,000 Property Damage (PD) = $12,000 Source: Mn/DOT Office of Capital Programs and Performance Measures (July 2010) Office of Traffic, Safety and Technology

Study Results Property Damage Costs = $5,640, more property damage crashes after ( ) Fatal Crash Costs = $92,300, fewer Fatalities after Office of Traffic, Safety and Technology

Crash Costs 1 Cross median fatality where cable median is installed (unrestrained driver) 1 life saved for every 17 miles of installed cable median (annually) 77 lives saved to date Office of Traffic, Safety and Technology

Minnesota Examples Office of Traffic, Safety and Technology

Minnesota Examples Office of Traffic, Safety and Technology Video 4

Maintenance Cable Placement o Out of the center of median o Shoulder placement Remove turn buckles rather than cut cable o Spaced approx o Each installation approx. 1 mile in length o 5 Opportunities to loosen cable per installation Cable cannot be re-spliced o Maintenance can take up to 6 weeks Office of Traffic, Safety and Technology

Extrication Difficulties Office of Traffic, Safety and Technology

Maintenance Training How to get slack in cable o Manipulate cable (tow service) o Posts – take out or cut o Turnbuckle Loosen Remove Cut o Spreader Bar For woven systems $300 from manufacturer Office of Traffic, Safety and Technology

Maintenance Training Stock piles of parts o Multiple shops o Multiple manufacturers Steamers to remove posts in ice Training video on cutting cable Communication o First responders o Maintenance o Design o Location of turn-arounds Office of Traffic, Safety and Technology

Minnesota Links MN Office of Traffic, Safety, and Technology (OTST) – Solicitations –Greater MN & Metro Announcements & Applications –

Contact Information Julie Whitcher MN Office of Traffic, Safety, and Technology (OTST) – Office of Traffic, Safety and Technology