Ben BuchanGeorgia DOT
AASHTO Subcommittee on Design
June 27, 2005
Report on the
Update to NCHRP Report 350
Primary Issues
• Test Vehicles.
• Impact Conditions.
• Deformation/Intrusion.
• Occupant risk.
• Soil specifications.
• Critical impact points.
• Test specifications.
• Reporting requirements.
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
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.
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.
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)
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
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).
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
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
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
Standard W-beam Guardrail
Standard W-beam Guardrail
Midwest Guardrail System
Midwest Guardrail System
Free Standing Temporary Barrier
Evaluation of 25 deg.
Impact Angle w/ NJ Barrier
Evaluation of 25 deg. Impact Angle
w/ MGS Guardrail Mounted at 32”
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
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.)
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.
Other Recommendations
• Require better tracking of material mill certifications.
• Improve documentation of
�Test article construction.
�Component strength.
�Soil type and condition.
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.
QUESTIONS?
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