report on the update to nchrp report 350 - american...

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?