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Best Practices A comparison of Mobile Barriers MBT-1 & Caltrans Balsi Beam.

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Presentation on theme: "Best Practices A comparison of Mobile Barriers MBT-1 & Caltrans Balsi Beam."— Presentation transcript:

1 Best Practices A comparison of Mobile Barriers MBT-1 & Caltrans Balsi Beam

2 Mobile Barriers would like to thank The FHWA Office of Safety for their review and comments prior to finalization of this comparison. Mobile Barriers would also like to thank members of Task Force 13 the joint subcommittee of The Associated General Contractors of America (AGC) The American Road & Transportation Builders Association (ARTBA) & The American Association of State Highway and Transportation Officials (ASSHTO) for their thoughts and comments.

3 Basic Comparison Mobile Barriers MBT-1Caltrans Balsi Beam Tested: MASH TL-3No NCHRP 350TL-3TL-2 (w/ issues) FHWA ReviewedYesNo FHWA Acceptance/Eligibility LtrYesNo Impact Severity Tested 150 kJ (110,600 ft-lbf)19/66 kJ (13,700-48,800 ft-lbf) (for context, standards for NCHRP 350 TL3 Pickups & TL-4 Straight Trucks ranged from kJ) Barrier Work Area20-80’20-30’ OAL40-100’40-50’ Barrier Height 5’3’ Weight 50,000 lbsest. 20,000 lbs TractorAny Standard TractorSpecially Modified Tractor Required Mobility/Moving OpsFully MobileImmobile (tractor locked/jack stands down) Time to Deploy/Remove (min)0 (park & work)20 Min (lock tractor, drop jacks, rotate arms) (inherent danger/vulnerability) Mechanical ProblemsNothing Material Lock Up on Setup/Removal (arms lock in rotation and extension ) Bolt Sheer & Other Issues also reported Test issues - old vehicles, snagging, exit Features/Options20’ Decks & Lockable Storage Onboard Power, Air & Lights Signage & TMA CostSignificantly Less & Modular

4 Larger Compare Balsi Beam Small enough to enclose ( short or extended ) Half the height (3’ vs 5’)

5 MBT-1… Taller/Heavier/Stronger Shoulder vs Waist High Balsi

6 MBT-1… Better Physical & Visual Barrier Traffic cant see in (better traffic flows) Crews can still see out Balsi Less Physical & Less Visual Barrier

7 MBT-1… On-board: Power - 120/240, solar & batteries, Air – enough for jackhammer, impact wrenches & tools Lights – great lighting – better than traditional 4 head arrays (ASSE study) Storage – lockable storage & 20’ decks for materials & supplies Signage & TMA (typically TL-3) Balsi

8 MBT-1 in the Real World – After 2 Semi Truck Hits Minor damage ($2000 & scratches) Both trucks ran down, along and off the wall under control (one drove on/one stopped) Semi impact… higher than Balsi wall

9 MBT-1 Turns and Redirects Cleanly (MASH TL-3: 5000 lbs/63 mph)

10 MBT-1 Fully Operable After Crash Balsi – Jammed

11 MBT-1 … clean – no snagging – extra wall height helped control impact (MASH TL-3: 5000 lbs/63 mph/25°)

12 Balsi - Snagging only TL-2: 4000 lbs/43 mph/25°) (Report says 1.5 degrees)

13 Balsi - Snagging (only 44 mph/21°)

14 MBT-1 TL-3/63 mph Impact Severity: 150 kJ Balsi TL-2/43 mph Impact Severity: 66 kJ (pickup) 19 kJ (car) MBT-1 … Balsi Side by Side

15 MBT-1 … Balsi Side by Side MBT-1 TL-3/63 mph Impact Severity: 150 kJ No Snagging Balsi TL-2/43 mph Impact Severity: 66 kJ (pickup) 19 kJ (car) Snagging

16 MBT-1… Modular (repair/replace only what’s damaged) Repair/Replacement Balsi... Not Modular Replace a Balsi? $675,000 Replace: a Wall? $25,000 a Caboose? $55,000 or a Platform? $75,000

17 Fixed vs Articulating Wall Advantage or Detriment? MBT-1 Theory: Stronger, Simpler & More Efficient Balsi Theory: Crews Can Work Either Side In Practice: Crews Don’t… Becomes Detriment Crews Plan Work & Work Zones Setups Lock, Align, Extend & Rotate Adds 20 min of Hazardous Setup Each Arrival/Departure – Each Site On Road/In Traffic/In Work Zone Most Dangerous Location to Configure Single Beam only 24” High – Real Risk of Penetration Complexity adds to Lockup/Failure & Decreases Strength Lockup Compounds Danger – Joints Decrease Strength Vulnerability adds Danger for Crews & Passing Traffic Complexity Adds Cost to Build, Operate & Maintain $675,000 In Practice: Exactly That… Pull In & Work Simple to Operate & Maintain Crews Plan Work & Work Zone Setups Easily Reconfigured to Right or Left when Necessary All Configuration Out of Traffic In Secure Area (30 min or less when familiar) Rigidity Adds to Strength Simplicity allows for Storage, Lighting, Power & Air Simplicity Allows for More Economical Price Easier to Build & Maintain Half the Cost (or Less) & Modular

18 MBT-1… Easily reconfigured for Right or Left work depending on end to which tractor is attached. Tractor can attach at either end. Rear Axle Assembly (“Caboose”) moves and attaches to end opposite tractor. For animation of reconfiguration, see “Reconfiguration” page at

19 Balsi … TL-2 only Crash Rpt Recommendations (pg 31) “It is recommended that the [Balsi] be outfitted with a truck-mounted attenuator (TMA) and followed with a shadow vehicle that also has a TMA. This is recommended because no testing was done on the [Balsi] to ensure that a rear hit on a deployed system will not collapse the system.” But… Balsi Flier (No-Boundaries)…no TMA TMA MBT-1 … TL-2 or TL-3 (real world speeds - real world impacts) TMA

20 Balsi …TL-2 only Crash Rpt Recommendations (pg 31) Use limited to locations where “the potential for vehicle impacts to not exceed Test Level 2 conditions (i.e. under 70 km/h (43 mph).” TL-2 at Interstate Speeds?? Using TL-2 TMA’s for Interstate Work? CA is one of few that still does. Most don’t. Typical Interstate Speeds exceed 43 mph TL-2 levels (and are rarely posted down to that level) MBT-1 … TL-2 or TL-3 (real world speeds - real world impacts) USAGE

21 Mobile Barriers MBT-1Caltrans Balsi Beam Tested: MASH TL-3No NCHRP 350TL-3TL-2 (w/ issues) FHWA ReviewedYesNo FHWA Acceptance/Eligibility LtrYesNo Impact Severity Tested 150 kJ (110,600 ft-lbf)19/66 kJ (13,700-48,800 ft-lbf) (for context, standards for NCHRP 350 TL3 Pickups & TL-4 Straight Trucks ranged from kJ) Barrier Work Area20-80’20-30’ OAL40-100’40-50’ Barrier Height 5’3’ Weight 50,000 lbsest. 20,000 lbs TractorAny Standard TractorSpecially Modified Tractor Required Mobility/Moving OpsFully MobileImmobile (tractor locked/jack stands down) Time to Deploy/Remove (min)0 (park & work)20 Min (lock tractor, drop jacks, rotate arms) (inherent danger/vulnerability) Mechanical ProblemsNothing Material Lock Up on Setup/Removal (arms lock in rotation and extension ) Bolt Sheer & Other Issues also reported Test issues - old vehicles, snagging, exit Features/Options20’ Decks & Lockable Storage Onboard Power, Air & Lights Signage & TMA CostSignificantly Less & Modular Recap

22 Best Practice


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