Report on the Update to NCHRP Report 350 - American...
Transcript of Report on the Update to NCHRP Report 350 - American...
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Ben BuchanGeorgia DOT
AASHTO Subcommittee on Design
June 27, 2005
Report on the
Update to NCHRP Report 350
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Primary Issues
• Test Vehicles.
• Impact Conditions.
• Deformation/Intrusion.
• Occupant risk.
• Soil specifications.
• Critical impact points.
• Test specifications.
• Reporting requirements.
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Test Vehicle Selection
• Light truck:
�¾ ton pickups weigh more than 2000 kg.
• Small car:
�No 820 kg vehicles.
• Midsize vehicles:
�Concern about staged attenuation devices.
• TL-3 Strength Test More Severe than TL-4
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2000P Test Vehicle
• ~ 22% of all vehicles sold in 2002
weighed more than 2000 kg (4400 lb).
• 12% of light trucks and 6.2% of all
vehicles sold in 2002 weighed more than
2270 kg (5000 lb).
• Recommend that new test vehicle weigh
near 2270 kg (5000 lb) – Same as ¾-ton
regular cab and ½-ton crew cab pickups.
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Proposed Test Vehicle
• 4-door ½-ton crew cab pickups weigh 5000 lb.
• Higher c. g. – more representative of large SUV’s.
• High sales volumes.
• Higher cost.
• Loss of knowledge base on ¾-ton regular cab pickups.
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Light Truck C.G. HeightsCurb C.G. Height
Make/Model Weight, kg (lb) mm (in.)
Dodge Ram Van 2188 (4820) 743 (29.2)
Ford Expedition 2391 (5267) 742 (29.2)
Chev. Tahoe (2WD)* 2292 (5050) 742 (29.2)
Toyota Sequoia 2301 (5070) 734 (28.9)
Chev. Suburban* 2246 (4947) 734 (28.9)
Land Rover Discovery 2157 (4752) 731 (28.6)
Mitsubishi Montero 2173 (4788) 696 (27.4)
Dodge Durango 2203 (4852) 680 (26.8)
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Quad Cab Pickups (2WD)
Curb C.G. Height
Make/Model Weight, kg (lb) mm (in.)
2002 Chev. Avalanche* 2507 (5523) 741 (29.2)
2002 Ford F150* 2195 (4836) 693 (27.3)
2002 Dodge Ram 1500* 2314 (5098) 720 (28.4)
2002 Ford F150# 2162 (4761) 682 (26.8)
2002 Dodge Ram 1500 2296 (5057) 718 (28.3)
2002 Dodge Ram 1500 2286 (5035) 722 (28.4)
* - reported by NHTSA
# - worn tires
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PROPOSED SMALL CAR
TEST VEHICLE
• Small passenger car test vehicle should
be representative of the 98th percentile
smallest vehicle by sales volume.
• Increase weight of small passenger car
test vehicle to 1100 kg (2420 lb).
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PROPOSED TL-4
TEST Conditions
• Under Report 350, TL-4 test less severe than
TL-3.
• Increasing pickup truck mass will aggravate
problem
• Propose to increase mass of single unit truck
from 8000 kg to 12000 kg and increase test
speed from 80 km/hr to 100 km/hr
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Impact Speed
Impact Speed (km/h)
Source > 100 > 110
Pole/Narrow Bridge Study
Rural Arterial 0.1445 0.1082
Freeway 0.1800 0.1200
NASS CDS, SL > 55 mph
Raw 0.0793 0.0412
Weighted 0.1091 0.0642
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IMPACT SPEED & ANGLE
• Recent data collected under high speed limit
conditions does not indicate significantly higher
impact speeds
• Data does not support lowering impact angles
• No support for lower impact angles for small
passenger vehicles
• Propose 100 km/hr and 25 deg. testing for both
light truck and small car test vehicles
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Standard W-beam Guardrail
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Standard W-beam Guardrail
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Midwest Guardrail System
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Midwest Guardrail System
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Free Standing Temporary Barrier
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Evaluation of 25 deg.
Impact Angle w/ NJ Barrier
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Evaluation of 25 deg. Impact Angle
w/ MGS Guardrail Mounted at 32”
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Deformation/Intrusion Issues
• NCHRP Report 350 criteria not well defined and
subjective in nature.
• FHWA guidelines on deformation/intrusion and
windshield damage are state of practice
• Deformation/intrusion an issue with 2000P test
vehicle.
• Windshield damage an issue with temporary work
zone traffic control devices.
• Insurance Institute for Highway Safety allows
greater deformation than FHWA guidelines
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Proposed Guidelines
• No penetration into occupant compartment allowed
• Roof deformation limited to 100 mm (4 in.)
• Elsewhere - generally follow IIHS guidelines
Location Maximum Deformation
Wheel well & toe pan < 22.5 cm (9 in.)
Side above seat < 22.5 cm (9 in.)
Side below seat < 30 cm (12 in.)
Side forward of A pillar < 30 cm (12 in.)
Transmission tunnel < 30 cm (12 in.)
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Proposed Guidelines
• No breakage of side window due to contact
with test article.
• Windshield:
�No tearing of plastic liner.
�Maximum deformation of 3 in.
�Apply FHWA vision obstruction criteria to
work zone traffic control devices only.
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Other Recommendations
• Require better tracking of material mill certifications.
• Improve documentation of
�Test article construction.
�Component strength.
�Soil type and condition.
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Other Recommendations
• Require in-situ soil testing.
• Develop new critical impact location.
guidelines for transitions, terminals, and
gating crash cushions.
• Test TMA’s with maximum allowable support
truck mass.
• Test breakaway structures at most severe
angle up to 90 degrees.
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QUESTIONS?