best practices a comparison of mobile barriers mbt-1
DESCRIPTION
Best Practices A comparison of Mobile Barriers MBT-1. & Caltrans Balsi Beam. 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 - PowerPoint PPT PresentationTRANSCRIPT
Best PracticesA comparison of
Mobile Barriers MBT-1
& Caltrans Balsi Beam
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 ofThe 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.
Basic Comparison
Mobile Barriers MBT-1 Caltrans Balsi BeamTested:
• MASH TL-3 No• NCHRP 350 TL-3 TL-2 (w/ issues)• FHWA Reviewed Yes No• FHWA Acceptance/Eligibility Ltr Yes No
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 132-138 kJ)Barrier
• Work Area 20-80’ 20-30’• OAL 40-100’ 40-50’• Barrier Height 5’ 3’ • Weight 50,000 lbs est. 20,000 lbs
Tractor Any Standard Tractor Specially Modified Tractor Required
Mobility/Moving Ops Fully Mobile Immobile (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 Problems Nothing Material Lock Up on Setup/Removal(arms lock in rotation and extension )Bolt Sheer & Other Issues also reportedTest issues - old vehicles, snagging, exit
Features/Options 20’ Decks & Lockable StorageOnboard Power, Air & LightsSignage & TMA
Cost Significantly Less & Modular
Larger
Compare Balsi Beam• Small enough to enclose (short or extended)• Half the height (3’ vs 5’)
MBT-1… Taller/Heavier/Stronger
Shoulder vs Waist High
Balsi
MBT-1… Better Physical & Visual BarrierTraffic cant see in (better traffic flows)
Crews can still see out
BalsiLess Physical &
Less Visual Barrier
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
MBT-1 in the Real World – After 2 Semi Truck HitsMinor 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
MBT-1 Turns and Redirects Cleanly (MASH TL-3: 5000 lbs/63 mph)
MBT-1Fully Operable After Crash
Balsi – Jammed
MBT-1 … clean – no snagging – extra wall height helped control impact(MASH TL-3: 5000 lbs/63 mph/25°)
Balsi - Snagging (@ only TL-2: 4000 lbs/43 mph/25°)
(Report says 1.5 degrees)
Balsi - Snagging (only TL-2 @ 44 mph/21°)
MBT-1TL-3/63 mphImpact Severity: 150 kJ
BalsiTL-2/43 mphImpact Severity: 66 kJ (pickup)
19 kJ (car)
MBT-1 … BalsiSide by Side
MBT-1 … BalsiSide by Side
MBT-1TL-3/63 mphImpact Severity: 150 kJ
No Snagging
BalsiTL-2/43 mphImpact Severity: 66 kJ (pickup)
19 kJ (car)
Snagging
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? $55,000or a Platform? $75,000
Fixed vs Articulating WallAdvantage or Detriment?
MBT-1Theory: Stronger, Simpler & More Efficient
BalsiTheory: Crews Can Work Either Side
In Practice: Crews Don’t… Becomes Detriment Crews Plan Work & Work Zones Setups
Lock, Align, Extend & RotateAdds 20 min of Hazardous Setup
Each Arrival/Departure – Each SiteOn Road/In Traffic/In Work Zone
Most Dangerous Location to ConfigureSingle Beam only 24” High – Real Risk of Penetration
Complexity adds to Lockup/Failure & Decreases StrengthLockup Compounds Danger – Joints Decrease StrengthVulnerability adds Danger for Crews & Passing TrafficComplexity Adds Cost to Build, Operate & Maintain
$675,000
In Practice: Exactly That… Pull In & WorkSimple to Operate & Maintain
Crews Plan Work & Work Zone SetupsEasily Reconfigured to Right or Left when Necessary
All Configuration Out of Traffic In Secure Area(30 min or less when familiar)
Rigidity Adds to StrengthSimplicity allows for Storage, Lighting, Power & Air
Simplicity Allows for More Economical PriceEasier to Build & Maintain
Half the Cost (or Less) & Modular
MBT-1… Easily reconfigured for Right or Left workdepending 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 www.mobilebarriers.com
Balsi … TL-2 onlyCrash 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
TMAMBT-1 … TL-2 or TL-3 (real world speeds - real world impacts)
TMA
Balsi …TL-2 onlyCrash 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
Mobile Barriers MBT-1 Caltrans Balsi BeamTested:
• MASH TL-3 No• NCHRP 350 TL-3 TL-2 (w/ issues)• FHWA Reviewed Yes No• FHWA Acceptance/Eligibility Ltr Yes No
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 132-138 kJ)Barrier
• Work Area 20-80’ 20-30’• OAL 40-100’ 40-50’• Barrier Height 5’ 3’ • Weight 50,000 lbs est. 20,000 lbs
Tractor Any Standard Tractor Specially Modified Tractor Required
Mobility/Moving Ops Fully Mobile Immobile (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 Problems Nothing Material Lock Up on Setup/Removal(arms lock in rotation and extension )Bolt Sheer & Other Issues also reportedTest issues - old vehicles, snagging, exit
Features/Options 20’ Decks & Lockable StorageOnboard Power, Air & LightsSignage & TMA
Cost Significantly Less & Modular
Recap
Best Practice