Occupant

Dynamics

in

Rollover

Crashes

Influence

of

Roof

Deformation

and

Seat

Belt

Performance

on

Probable

Spinal

Column

Injury

Motor

vehicle

crashes

are

the

leading

cause

of

death

in

the

United

States

for

people

ages

and

rollover

crashes

have

a

higher

fatality

rate

than

any

other

crash

mode

At

the

request

and

under

the

sponsorship

of

Ford

Motor

Company

Autoliv

conducted

a

series

of

dynamic

rollover

tests

on

Ford

Explorer

sport

utility

vehicles

-LRB-

SUV

-RRB-

during

and

Data

from

those

tests

were

made

available

to

the

public

and

were

analyzed

in

this

study

to

investigate

the

magnitude

of

and

the

temporal

relationship

between

roof

deformation

lap

shoulder

seat

belt

loads

and

restrained

anthropometric

test

dummy

-LRB-

ATD

-RRB-

neck

loads

Introduction

Motor

vehicle

crashes

are

the

leading

cause

of

death

in

the

United

States

for

persons

of

every

age

from

through

Rollover

crashes

in

particular

have

a

higher

fatality

rate

than

any

other

crash

mode

Of

the

police

reported

crashes

in

in

the

United

States

only

involved

a

rollover

Yet

rollovers

accounted

for

-LRB-

-RRB-

of

all

passenger

vehicle

fatalities

The

fatality

rate

-LRB-

defined

as

deaths

per

registered

vehicles

-RRB-

in

rollover

crashes

is

more

than

two

and

one-half

times

higher

in

sport

utility

vehicles

-LRB-

SUVs

-RRB-

than

in

passenger

cars

-LRB-

vs.

respectively

-RRB-

Another

individuals

sustained

serious

injuries

in

rollover

crashes

in

approximately

of

whom

were

occupants

of

SUVs

Measurement

tools

are

required

to

evaluate

appropriate

intervention

strategies

to

reduce

the

mortality

and

morbidity

associated

with

rollover

crashes

The

Abbreviated

Injury

Scale

-LRB-

AIS

-RRB-

and

Harm

value

-LRB-

HARM

-RRB-

are

two

such

measures

which

are

used

to

compare

injuries

of

different

types

and

severities

The

AIS

reflects

threat

to

life

-LRB-

or

risk

of

death

-RRB-

and

stratifies

injuries

into

six

categories

-LRB-

AIS

-RRB-

with

AIS

defined

as

an

untreatable

injury

The

maximum

AIS

-LRB-

MAIS

-RRB-

score

refers

to

the

most

severe

injury

sustained

in

a

specific

individual

The

highest

rate

of

seriously

injured

-LRB-

MAIS

-RRB-

children

years

old

occurs

in

rollovers

more

than

double

any

other

crash

mode

One

study

reported

that

despite

the

increased

weight

of

SUVs

the

risk

of

injury

for

children

in

SUVs

was

similar

to

that

for

passenger

cars

which

may

be

due

to

the

increased

tendency

of

SUVs

to

roll

over

HARM

is

a

mathematical

measure

that

applies

a

weighting

factor

to

each

injured

yet

surviving

occupant

which

includes

both

monetary

costs

of

the

injury

-LRB-

i.e.

direct

costs

associated

with

the

loss

of

wages

-RRB-

and

comprehensive

costs

-LRB-

i.e.

monetary

costs

plus

non-monetary

costs

-RRB-

Importantly

the

non-monetary

costs

include

such

measures

as

loss

of

functional

capacity

and

quality

of

life

In

rollover

crashes

the

highest

HARM

is

reflected

in

the

population

of

occupants

who

survive

the

crash

yet

sustain

catastrophic

injury

including

permanent

brain

and/or

spinal

cord

injury

A

major

source

of

HARM

in

rollover

crashes

results

from

occupant

contact

with

the

vehicle

roof

support

pillars

and

side

headers

According

to

Digges

et

al.

Countermeasures

to

reduce

rollover

casualties

include

increased

belt

use

and

technological

interventions

to

prevent

ejection

and

reduce

the

severity

of

body

contacts

with

the

vehicle

interior

Hugh

DeHaven

outlined

principles

for

designing

vehicles

for

human

transport

in

and

stated

that

the

package

-LRB-

the

passenger

compartment

-RRB-

should

not

collapse

under

expected

conditions

of

force

thereby

exposing

objects

-LRB-

and

people

-RRB-

inside

it

to

damage

Closely

related

to

this

principle

DeHaven

stated

that

the

packaging

structures

which

shield

the

inner

container

must

not

be

made

of

brittle

or

frail

materials

they

should

resist

force

by

yielding

and

absorbing

energy

applied

to

the

outer

container

so

as

to

cushion

and

distribute

impact

forces

and

thereby

protect

the

inner

container

reported

the

importance

of

maintaining

the

integrity

of

the

occupant

compartment

-LRB-

referred

to

as

survival

space

-RRB-

for

belted

occupants

during

a

crash

event

Few

studies

however

have

experimentally

evaluated

the

influence

of

dynamic

roof

deformation

with

concomitant

loss

of

occupant

survival

space

as

a

potentially

preventable

cause

of

head

and

cervical

spine

injuries

in

rollover

crashes

Bahling

et

al.

conducted

rollover

and

drop

tests

of

late

model

Chevrolet

Malibu

passenger

cars

using

lap

shoulder

belted

anthropomorphic

test

dummies

-LRB-

ATDs

-RRB-

to

evaluate

the

influence

of

roof

strength

on

injury

mechanics

In

several

studies

Moffatt

and

other

investigators

reported

on

a

customized

dynamic

test

procedure

with

controlled

roof

impacts

of

passenger

vans

and

sedans

Both

groups

concluded

that

potentially

injurious

impacts

-LRB-

defined

by

these

authors

as

N

recorded

by

the

ATD

upper

neck

sensor

-RRB-

occurred

prior

to

significant

roof

crush

and

that

enhanced

roof

strength

made

no

difference

in

the

likelihood

of

serious

neck

injury

to

restrained

occupants

These

conclusions

have

been

contradicted

in

other

literature

albeit

without

the

benefit

of

scientific

data

from

comparable

full-scale

dynamic

rollover

crash

tests

Recently

the

raw

data

from

a

series

of

full-scale

dynamic

rollover

tests

of

model

year

Ford

Explorer

SUVs

using

fully

instrumented

ATDs

were

made

publicly

available

to

the

scientific

community

These

tests

were

conducted

using

a

standardized

test

methodology

specified

by

Federal

Motor

Vehicle

Safety

Standard

-LRB-

FMVSS

-RRB-

of

the

U.S.

Department

of

Transportation

-LRB-

FMVSS

CFR

Ch

V

-LRB-

Edition

-RRB-

-RRB-

These

data

provide

the

first

opportunity

to

analyze

the

dynamics

of

belted

occupants

within

a

contemporary

SUV

in

a

standardized

rollover

test

environment

The

authors

used

the

described

data

in

the

present

study

The

study

's

objective

was

to

investigate

both

the

magnitude

of

and

the

temporal

relationship

between

dynamic

roof

deformation

lap

shoulder

seat

belt

loads

and

restrained

ATD

neck

loads

in

these

FMVSS

dolly

rollover

tests

of

Ford

Explorer

SUVs

Materials

and

Methods

Three

full-scale

dolly

rollover

tests

of

Explorer

SUVs

were

sponsored

by

Ford

Motor

Company

and

conducted

at

the

North

American

Autoliv

test

according

to

the

standardized

FMVSS

test

protocol

This

standard

issued

by

the

National

Highway

Transportation

Safety

Administration

-LRB-

NHTSA

-RRB-

in

outlines

vehicle

crash

performance

requirements

designed

for

improving

occupant

protection

Described

within

FMVSS

is

a

voluntary

dolly

rollover

test

used

to

evaluate

occupant

protection

during

a

lateral

rollover

This

standardized

test

procedure

was

used

for

all

three

SUV

rollover

tests

The

FMVSS

test

procedure

involves

accelerating

a

rollover

dolly

carrying

a

test

vehicle

to

a

set

velocity

and

then

rapidly

decelerating

the

dolly

causing

the

vehicle

to

release

trip

and

enter

a

lateral

roll

The

SUVs

were

first

placed

on

a

dolly

fixed

with

a

rigid

angled

platform

positioned

in

from

the

ground

and

from

the

horizontal

To

assure

that

the

roll

was

driver-side

leading

-LRB-

i.e.

that

the

driver

's

side

contacted

the

ground

first

-RRB-

each

vehicle

was

situated

on

the

platform

so

that

its

driver

's

side

tires

rested

along

a

in

lip

at

the

forward

edge

of

the

test

platform

as

shown

in

Figs.

and

Figure

-LRB-

a

-RRB-

FMVSS

dynamic

rollover

pre-test

setup

of

SUV

test

on

a

dolly

rollover

cart

-LRB-

b

-RRB-

critical

dimensions

of

FMVSS

dolly

The

vehicle

and

dolly

were

then

accelerated

along

a

straight

path

perpendicular

to

the

longitudinal

axis

of

the

vehicle

The

dolly

was

then

decelerated

rapidly

-LRB-

minimum

deceleration

rate

of

g

for

s

-RRB-

resulting

in

vehicle

trip

and

subsequent

rollover

The

target

speed

for

all

Explorer

tests

was

mph

The

vehicle

identification

number

-LRB-

VIN

-RRB-

and

actual

dolly

launch

velocity

for

each

of

the

three

tests

are

summarized

in

Table

Table

conditionsAutoliv

test

numberTest

descriptionData

sampling

rateSampling

durationTest

dateAccelerometerCoordinates

-LRB-

mm

-RRB-

Rollover

-LRB-

-RRB-

-LRB-

mph

-RRB-

Hz

of

Driver

's

rail

at

Driver

's

rail

at

Driver

's

rail

at

Passenger

's

rail

at

Passenger

's

rail

at

Passenger

's

rail

at

Rollover

-LRB-

-RRB-

-LRB-

mph

-RRB-

Hz

of

Driver

's

rail

at

Driver

's

rail

at

Driver

's

rail

at

Passenger

's

rail

at

Passenger

's

rail

at

Passenger

's

rail

at

Rollover

-LRB-

-RRB-

-LRB-

mph

-RRB-

Hz

of

Driver

's

rail

at

Driver

's

rail

at

Driver

's

rail

at

Passenger

's

rail

at

Passenger

's

rail

at

Passenger

's

rail

at

Vehicle

and

ATD

Instrumentation

Triaxial

and

biaxial

accelerometers

were

installed

in

each

SUV

to

measure

vehicle

structural

dynamics

during

the

rollover

tests

Accelerations

were

recorded

at

each

of

the

following

vehicle

structure

locations

in

coordinate

systems

consistent

with

SAE

guidelines

-LRB-

SAE

REV

-RRB-

as

shown

in

Figs.

and

and

Table

Center

of

Gravity

-LRB-

CG

-RRB-

-LRB-

x

y

z

-RRB-

Left

-LRB-

driver

-RRB-

roof

rail

at

A-pillar

-LRB-

y

z

-RRB-

B-pillar

-LRB-

y

z

-RRB-

C-pillar

-LRB-

y

z

-RRB-

Right

-LRB-

passenger

-RRB-

roof

rail

at

A-pillar

-LRB-

y

z

-RRB-

B-pillar

-LRB-

y

z

-RRB-

C-pillar

-LRB-

y

z

-RRB-

Figure

-LRB-

a

-RRB-

Exterior

view

of

test

vehicle

indicating

A

B

and

C-pillars

-LRB-

b

-RRB-

interior

view

of

test

vehicle

accelerometers

were

mounted

at

the

roof

rail-to-pillar

junction

at

the

A

B

and

C-pillars

for

both

driver

and

passenger

sides

of

the

Ford

Explorer

SUVs

In

each

test

two

Hybrid

III

percentile

male

instrumented

ATDs

were

placed

in

the

front

seats

of

Ford

Explorer

SUVs

and

restrained

with

lap

shoulder

belts

that

were

affixed

with

load

cells

Time

synchronized

with

all

other

sensors

and

cameras

in

the

experimental

setup

these

load

cells

continuously

recorded

tensile

forces

in

the

webbing

of

the

lap

and

shoulder

belts

Both

ATDs

were

positioned

in

their

respective

seats

according

to

reference

FMVSS

Dummy

Positioning

Procedure

with

the

seats

located

in

the

mid-track

position

Given

that

the

vehicle

was

positioned

to

roll

driver-side

leading

the

driver

ATD

represented

the

near-side

occupant

and

the

passenger

ATD

the

far-side

occupant

in

this

test

series

The

following

sensor

outputs

were

recorded

continuously

throughout

each

rollover

test

for

both

driver

and

passenger

ATDs

Head

CG

acceleration

-LRB-

x

y

z

-RRB-

Upper

Neck

Force

-LRB-

x

y

z

-RRB-

Moment

-LRB-

x

y

z

-RRB-

Lower

Neck

Force

-LRB-

x

y

z

-RRB-

Moment

-LRB-

x

y

z

-RRB-

Chest

Acceleration

-LRB-

x

y

z

-RRB-

DeflectionPelvis

Acceleration

-LRB-

x

y

z

-RRB-

Femur

Force

-LRB-

Fz

right

and

left

-RRB-

Dynamic

motion

of

the

SUVs

was

visually

recorded

by

up

to

high

speed

external

cameras

which

were

time

synchronized

with

the

cart

release

trigger

and

imaged

at

frames/s

-LRB-

Fig.

-RRB-

Clocks

that

were

positioned

along

the

test

track

were

visible

in

the

external

camera

views

throughout

the

roll

sequence

Targets

were

affixed

to

the

rear

aspect

of

the

driver

and

passenger

ATD

heads

and

were

visible

by

the

same

camera

monitoring

the

onboard

time

clock

Up

to

three

onboard

high

speed

cameras

recorded

ATD

kinematics

as

a

function

of

time

using

the

onboard

clock

which

was

also

time

synchronized

with

the

cart

release

trigger

external

cameras

and

electronic

sensors

affixed

to

both

ATDs

the

seat

belts

and

the

SUV

structure

Figure

camera

setup

With

the

cart

positioned

according

to

FMVSS

specifications

the

data

acquisition

system

was

set

up

and

armed

for

trigger

Time

zero

for

all

data

acquisition

was

provided

by

a

contact

switch

at

both

shock

absorbers

to

indicate

the

start

of

cart

deceleration

The

data-sampling

rates

for

each

test

are

provided

in

Table

Data

Analysis

The

raw

ASCII

sensor

data

retrieved

from

the

ATD

and

vehicle-mounted

transducers

were

filtered

according

to

the

SAE

channel

filtering

class

-LRB-

CFC

-RRB-

requirements

to

remove

the

effects

of

crash

related

noise

on

the

sensor

readings

Each

CFC

specifies

that

the

channel

frequency

response

lies

within

limits

detailed

in

SAE

Neck

forces

neck

moments

and

vehicle

data

were

filtered

at

CFC

CFC

and

CFC

accordingly

Subsequently

the

filtered

vehicle

acceleration

data

were

transformed

into

a

vehicle-fixed

center-of-gravity

coordinate

system

using

MATLAB

-LRB-

registered

trademark

of

The

Mathworks

Inc.

-RRB-

Roof

rail

accelerations

were

transformed

by

subtracting

the

center

of

gravity

accelerations

from

each

measurement

as

a

function

of

time

The

result

of

the

transformations

was

the

acceleration

of

the

roof

rail

relative

to

the

vehicle

's

center

of

gravity

The

transformed

roof

rail

acceleration

values

provided

insight

into

when

and

in

what

direction

the

rail

was

moving

Transformed

data

was

then

compared

to

the

ATD

neck

and

seat

belt

loads

as

a

function

of

time

The

accelerations

recorded

by

the

rail

sensors

were

influenced

by

both

vehicle

rotation

-LRB-

angular

velocity

-RRB-

and

localized

pillar

deformation

The

contribution

due

to

vehicle

rotation

was

made

at

a

low

frequency

given

that

the

peak

roll

rate

of

the

vehicle

at

any

time

during

the

test

interval

-LRB-

ms

-RRB-

was

approximately

s

-LRB-

i.e.

less

than

Hz

-RRB-

Thus

all

higher

frequency

accelerations

were

necessarily

due

to

localized

structural

deformation

The

sensor

outputs

from

the

driver

and

passenger

roof

rail

accelerometers

positioned

at

the

B-pillar

were

used

as

a

quantitative

definition

of

roof

intrusion

-LRB-

i.e.

objective

roof

crush

-RRB-

into

the

occupant

survival

space

The

mathematically

transformed

driver

and

passenger

roof

rail

acceleration

tracings

in

the

present

study

provided

objective

evidence

of

the

time

interval

-LRB-

s

-RRB-

when

roof/pillar

deformation

occurred

and

the

time

of

deformation

was

corroborated

through

careful

scrutiny

of

the

high

speed

video

images

-LRB-

observable

roof

crush

-RRB-

Objective

roof

crush

in

our

study

was

defined

under

the

following

necessary

contemporaneous

conditions

Vertical

and/or

lateral

rail

acceleration

peak

-LRB-

s

-RRB-

downward

and/or

inboard

toward

the

restrained

ATDExternal

camera

video

images

consistent

with

SUV

roof-to-ground

contactOnboard

camera

video

images

consistent

with

a

compromise

in

occupant

survival

space

-LRB-

i.e.

reduced

headroom

-RRB-

Roof

rail

accelerations

seat

belt

loads

and

peak

ATD

axial

neck

force

-LRB-

Fz

axial

compression/tension

-RRB-

and

moments

-LRB-

My

chin-to-chest

flexion

and

Mx

ear-to-shoulder

lateral

bending

-RRB-

were

compared

to

the

high-speed

video

data

to

validate

the

correlation

in

time

between

the

presence

of

objective

roof

crush

and

the

development

of

peak

ATD

neck

and

seat

belt

loads

Results

Results

are

presented

and

discussed

for

the

first

full

second

of

the

roll

sequence

for

each

of

the

three

SUV

tests

which

includes

the

initial

driver-side-to-ground

contact

and

full

roof

contact

followed

by

the

first

passenger-side-to-ground

contact

In

all

three

tests

the

external

high-speed

cameras

recorded

continuous

roof-to-ground

contact

from

the

first

contact

of

the

driver

's

roof

rail

with

the

ground

until

the

end

of

the

ms

period

which

corresponded

to

approximately

roll

Onboard

high

speed

video

cameras

recorded

the

front

passenger

compartment

of

each

SUV

capturing

the

kinematics

of

the

ATDs

as

well

as

the

deformation

of

the

roof

header

and

side

roof

rails

during

the

rollover

event

These

cameras

recorded

inboard

displacement

of

roof

rails

-LRB-

observable

roof

crush

-RRB-

of

both

driver

and

passenger-side

roof

rails

during

the

respective

roof

rail-to-ground

contact

for

all

three

tests

The

onboard

clock

which

was

recorded

by

the

interior

cameras

allowed

for

a

time-synchronized

comparison

of

this

data

to

the

sensor

output

of

the

ATD

neck

transducers

and

roof

rail

accelerometers

In

all

three

tests

the

head

of

each

lap

shoulder

belt

restrained

ATD

-LRB-

driver

and

passenger

-RRB-

contacted

the

roof

two

or

more

times

during

the

first

ms

roll

interval

as

indicated

by

increased

neck

compression

loads

-LRB-

negative

Fz

values

-RRB-

recorded

by

the

ATDs

upper

neck

sensor

-LRB-

Fig.

-RRB-

The

time

of

occurrence

of

each

peak

neck

load

for

the

driver

and

passenger

ATD

head-to-roof

contacts

-LRB-

the

Local

Maximum

as

well

as

the

Absolute

Maximum

or

Peak

neck

loads

-RRB-

was

consistent

with

the

onboard

high

speed

video

data

For

each

of

the

three

tests

the

time

recorded

by

the

onboard

camera

during

observable

ATD

head-to-roof

contact

was

within

ms

of

the

time

recorded

by

the

neck

sensors

for

peak

neck

loads

Peak

axial

neck

force

data

-LRB-

Fz

-RRB-

were

measured

by

the

ATDs

upper

neck

sensors

and

the

moment

loads

-LRB-

My

and

Mx

-RRB-

were

measured

by

the

ATDs

lower

neck

sensors

-LRB-

Table

-RRB-

Figure

upper

neck

Fz

vs.

time

-LRB-

Test

-RRB-

Table

of

Local

and

Absolute

maximum

-LRB-

Peak

-RRB-

neck

loads

-LRB-

during

time

interval

of

continuous

roof-to-ground

contact

-RRB-

Test

peak

Fz

-LRB-

N

-RRB-

a

peak

-LRB-

s

-RRB-

Fz

peak

My

-LRB-

N

m

-RRB-

peak

-LRB-

s

-RRB-

peak

Mx

-LRB-

N

m

-RRB-

peak

-LRB-

s

-RRB-

Mx

to

to

was

measured

at

the

dummy

upper

neck

load

cell

My

and

Mx

measured

at

the

lower

load

cellbIn

Test

no

absolute

maximum

Fz

was

identified

as

all

peak

neck

compression

loads

were

within

the

range

of

N

The

near-side

-LRB-

i.e.

the

driver

-RRB-

ATD

recorded

Peak

axial

neck

compression

-LRB-

Fz

-RRB-

loads

of

N

or

less

for

all

three

tests

Peak

neck

flexion

-LRB-

My

-RRB-

loads

for

the

driver

ATD

resulted

in

chin-toward-chest

head

motion

and

were

within

a

range

of

N

m

for

all

three

tests

In

contrast

the

far-side

-LRB-

i.e.

the

passenger

-RRB-

ATD

recorded

Peak

neck

Fz

values

in

the

range

of

to

N

for

two

out

of

three

tests

In

Test

no

Absolute

Maximum

Fz

value

was

identified

as

all

Local

Maxima

compression

loads

were

within

the

range

of

to

N

The

Peak

neck

flexion

-LRB-

My

-RRB-

loads

recorded

by

the

passenger

ATDs

resulted

in

chin-toward-chest

head

motion

and

ranged

from

to

N

m

for

all

three

tests

The

Peak

lateral

neck

bending

ear-to-shoulder

-LRB-

Mx

-RRB-

loads

ranged

from

to

N

m

for

the

passenger

ATD

and

the

driver

experienced

Mx

load

magnitudes

in

the

range

of

to

N

m

for

all

three

tests

The

time

of

occurrence

of

objective

vertical

and

lateral

roof

crush

was

identified

by

the

roof

rail

acceleration

peak

for

both

the

passenger

and

driver

side

roof

rails

in

all

three

tests

-LRB-

Table

-RRB-

Objective

roof

crush

occurred

prior

to

the

Absolute

Maximum

dummy

neck

loads

-LRB-

Fz

My

Mx

-RRB-

in

each

of

the

three

tests

for

both

driver

and

passenger

ATDs

-LRB-

Table

Fig.

-RRB-

The

far-side

passenger

ATD

recorded

Peak

neck

loads

within

ms

following

the

time

of

occurrence

of

objective

roof

crush

for

all

three

tests

Peak

neck

loads

for

the

near-side

driver

ATD

occurred

up

to

ms

following

the

time

of

occurrence

of

objective

roof

crush

for

all

three

tests

Table

of

occurrence

-LRB-

ms

-RRB-

of

roof/pillar

deformation

and

absolute

maximum

neck

loadsTest

roof/pillar

deformation

-LRB-

vertical

acceleration

peaks

-RRB-

roof/pillar

deformation

-LRB-

lateral

acceleration

peaks

-RRB-

isolated

spike

in

acceleration

was

noted

however

a

sustained

level

of

roof

deformation

is

reflected

in

the

roof

rail

tracings

and

the

video

footage

for

this

testbNo

isolated

absolute

maximum

Fz

value

was

noted

which

differed

significantly

from

the

other

local

maximums

This

was

consistent

with

the

very

high

peak

My

in

this

test

however

which

was

noted

at

ms

-LRB-

see

Table

-RRB-

cFz

was

measured

at

the

upper

neck

load

cell

whereas

My

and

Mx

were

measured

at

the

lower

neck

load

cellsFigure

upper

neck

Fz

vs.

vertical

acceleration

of

the

driver

rail

at

B-pillar

-LRB-

Test

-RRB-

Lap

and

shoulder

belt

loads

were

recorded

for

both

driver

and

passenger

ATDs

in

all

three

tests

with

the

exception

of

the

driver

's

shoulder

belt

for

test

and

passenger

shoulder

belt

for

test

both

of

which

experienced

sensor

failures

-LRB-

Table

-RRB-

The

Peak

lap

belt

loads

for

the

near-side

driver

ATD

occurred

within

ms

of

the

time

of

Peak

Fz

and

My

neck

loads

for

two

out

of

three

tests

-LRB-

Figs.

-RRB-

In

the

remaining

test

-LRB-

-RRB-

the

Peak

lap

belt

load

occurred

ms

prior

to

the

time

that

peak

neck

Fz

and

My

neck

loads

occurred

in

the

driver

ATD

In

contrast

the

far-side

passenger

ATDs

Peak

lap

belt

loads

occurred

ms

prior

to

the

time

of

Peak

neck

compression

-LRB-

Fz

-RRB-

for

two

out

of

three

tests

and

ms

prior

to

the

time

of

Peak

neck

flexion

-LRB-

My

-RRB-

for

all

three

tests

-LRB-

Fig.

-RRB-

In

Test

the

passenger

's

Peak

lap

belt

load

occurred

ms

after

the

time

of

Peak

neck

compression

yet

ms

before

the

Peak

neck

flexion

load

-LRB-

My

-RRB-

Table

belt

loads

compared

to

belt

loads

at

time

of

absolute

maximum

-LRB-

peak

-RRB-

neck

loadsTest

lap

belt

-LRB-

N

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

Peak

shoulder

belt

-LRB-

N

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

N/AaPeak

FzLap

belt

-LRB-

N

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

Shoulder

belt

-LRB-

N

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

N/AaPeak

My

-LRB-

N

m

-RRB-

Lap

belt

-LRB-

N

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

Shoulder

belt

-LRB-

N

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

-LRB-

ms

-RRB-

N/AaaData

not

available

due

to

transducer

failureFigure

lap

belt

and

neck

load

vs.

time

-LRB-

Test

-RRB-

Figure

percentile

Hybrid

III

Driver

ATD

diving

into

roof

with

lap

and

shoulder

belt

providing

restraining

forces

which

reduces

neck

loadFigure

-LRB-

a

-RRB-

Roof

crush

passenger

lap

belt

and

neck

load

vs.

time

-LRB-

Test

-RRB-

-LRB-

b

-RRB-

Roof

crush

passenger

shoulder

belt

and

neck

load

vs.

time

-LRB-

Test

-RRB-

The

driver

ATDs

Peak

lap

belt

loads

ranged

from

to

N

for

the

three

tests

and

the

shoulder

belt

loads

were

N

for

two

tests

-LRB-

the

driver

's

shoulder

belt

sensor

failed

on

Test

-RRB-

-LRB-

Table

-RRB-

The

passenger

ATDs

Peak

lap

belt

loads

were

similar

to

those

of

the

driver

ATDs

ranging

from

to

N

for

all

three

tests

the

shoulder

belt

loads

were

N

for

two

of

three

tests

-LRB-

the

passenger

's

shoulder

belt

sensor

failed

on

test

-RRB-

The

near-side

driver

ATD

lap

belt

loads

at

the

time

of

occurrence

of

the

Peak

Fz

and

My

neck

loads

were

of

the

ATDs

respective

Peak

lap

belt

load

for

all

three

tests

-LRB-

Table

-RRB-

In

contrast

the

far-side

passenger

ATD

lap

belt

loads

at

the

time

of

occurrence

of

the

Peak

neck

compression

-LRB-

Fz

-RRB-

were

less

than

of

the

passenger

ATDs

respective

Peak

lap

belt

load

recorded

for

two

of

the

three

tests

At

the

time

of

Peak

neck

flexion

-LRB-

My

-RRB-

the

lap

belt

loads

were

less

than

of

the

Peak

lap

belt

load

for

all

three

tests

Shoulder

belt

loads

for

both

driver

and

passenger

ATDs

at

the

time

of

occurrence

of

the

Peak

neck

Fz

and

My

were

of

the

ATDs

respective

Peak

shoulder

belt

loads

for

two

of

three

tests

-LRB-

load

cells

malfunctioned

in

the

driver

's

shoulder

belt

in

test

and

passenger

's

shoulder

belt

in

test

-RRB-

Discussion

The

three

rollover

tests

of

Ford

Explorer

SUVs

analyzed

in

the

present

study

represent

a

unique

dataset

evaluating

occupant

dynamics

in

rollover

crashes

as

represented

by

Hybrid

III

ATDs

To

the

authors

knowledge

this

study

represents

the

first

published

test

series

of

full-scale

rollover

crashes

of

a

contemporary

SUV

with

time

synchronized

sensor

output

from

ATD

neck

transducers

roof

rail

accelerometers

an

onboard

high

speed

clock

and

high

speed

external

and

internal

video

cameras

ATD

Biofidelity

The

biofidelity

of

the

Hybrid

III

ATD

in

rollover

crash

conditions

is

a

significant

limitation

of

this

study

as

well

as

other

published

rollover

however

ATD

sensor

data

may

be

carefully

evaluated

within

such

limitations

to

yield

objective

insights

The

ATDs

used

in

this

study

were

originally

designed

as

a

measurement

tool

in

frontal

crash

tests

not

rollovers

Thus

the

Hybrid

III

ATD

neck

was

designed

and

tested

primarily

to

simulate

dynamic

head

motion

in

the

sagittal

plane

-LRB-

neck

flexion

and

extension

-RRB-

The

Hybrid

III

ATD

neck

was

not

specifically

designed

to

produce

a

biofidelic

response

under

axial

compression

loading

typical

of

the

neck

loads

resulting

from

the

head-to-roof

contacts

observed

in

this

study

Researchers

have

shown

that

with

an

axially

directed

impact

to

the

crown

of

the

ATD

head

the

ATD

lower

neck

sensor

records

essentially

the

same

magnitude

axial

force

as

the

upper

neck

load

cell

whereas

the

human

cadaver

neck

lower

load

cell

records

a

much

reduced

load

magnitude

compared

to

the

upper

load

cell

Also

the

Hybrid

III

ATD

necks

are

neither

frangible

nor

viscoelastic

therefore

they

can

not

accurately

simulate

individual

vertebral

displacement

and/or

fracture

Notwithstanding

the

biomechanical

differences

between

the

necks

of

human

cadavers

and

ATD

mechanical

necks

the

Fz

measurements

of

the

upper

load

cell

of

a

restrained

Hybrid

III

dummy

may

provide

a

reasonable

estimate

of

the

initial

input

load

to

a

restrained

occupant

's

head

when

it

contacts

the

roof

in

a

rollover

crash

under

similar

dynamic

conditions

-LRB-

e.g.

impact

velocity

impact

duration

-RRB-

Given

that

the

mass

of

a

Hybrid

III

dummy

head

reasonably

mimics

that

of

the

comparable

human

-LRB-

percentile

male

in

the

present

study

-RRB-

the

inertial

effect

of

the

dummy

head

should

not

confound

Fz

readings

from

its

upper

neck

load

cell

In

all

three

tests

within

the

present

study

Fz

values

for

ATD

axial

neck

load

were

evaluated

solely

from

the

upper

neck

load

cells

thereby

taking

into

consideration

as

much

as

possible

the

significant

differences

in

axial

stiffness

between

the

ATD

and

cadaver

human

neck

-LRB-

the

lower

neck

Fz

sensor

was

not

evaluated

-RRB-

These

upper

neck

Fz

sensor

readings

were

interpreted

relative

to

the

head

impact

loads

in

cadaver

tests

under

similar

dynamic

conditions

-LRB-

described

below

-RRB-

Given

that

the

Hybrid

III

ATD

neck

was

specifically

designed

to

be

biofidelic

in

dynamic

sagittal

plane

bending

-LRB-

flexion

and

extension

-RRB-

loads

neck

flexion

loads

-LRB-

My

-RRB-

were

evaluated

in

this

study

from

the

lower

neck

load

cell

of

driver

and

passenger

ATDs

Lateral

bending

loads

-LRB-

Mx

-RRB-

were

recorded

and

reported

but

not

interpreted

in

this

study

due

to

the

lack

of

available

biomechanical

tolerance

data

for

the

human

spine

when

subjected

to

lateral

bending

Additional

research

in

this

important

area

for

both

rollover

and

side

impact

crashes

is

needed

Injury

Tolerance

of

the

Human

Cervical

Spine

Semantic

confusion

exists

in

the

published

literature

regarding

cervical

spine

tolerance

or

failure

load

Some

investigators

have

reported

cervical

spine

failure

loads

resulting

from

impacts

to

cadaver

heads

as

the

output

force

measured

at

the

lower

cervical

spine

thereby

neglecting

the

kinetic

energy

dissipation

associated

with

vertebral

fracture

and/or

subluxation

above

the

position

of

the

sensor

as

well

as

the

viscoelastic

response

of

the

intervertebral

discs

Other

studies

have

reported

both

the

input

and

output

loads

in

cadaver

tests

of

the

cervical

spine

These

data

provide

a

quantitative

comparison

of

the

significant

differences

between

the

input

loads

measured

at

the

cadaver

head

versus

what

might

be

more

appropriately

referred

to

as

the

residual

force

magnitude

that

is

recorded

at

the

base

of

the

cervical

spine

segment

No

experimental

cadaver

work

has

measured

and/or

estimated

the

input

loads

at

the

superior

aspect

of

the

human

neck

which

is

the

site

of

the

upper

neck

load

cell

in

the

Hybrid

III

dummy

when

the

head

is

subjected

to

an

axial

impact

on

the

crown

of

the

head

Additional

research

in

this

area

is

needed

The

confusion

of

terms

regarding

cervical

spine

failure

loads

in

the

published

literature

has

a

significant

bearing

on

the

proper

interpretation

of

Hybrid

III

ATD

axial

neck

load

sensor

output

in

controlled

rollover

tests

such

as

the

present

study

Bahling

et

al.

utilized

N

as

a

neck

sensor

Fz

threshold

for

potentially

injurious

impacts

-LRB-

PII

-RRB-

in

rollovers

which

is

in

the

range

of

the

published

residual

force

magnitude

recorded

at

the

lower

cervical

spine

following

an

injurious

impact

to

the

cadaver

head

In

contrast

other

investigators

reported

the

actuator

-LRB-

input

-RRB-

force

at

the

head

that

was

required

for

cervical

spine

injury

in

axial

compression

In

interpreting

the

ATD

neck

sensor

data

in

this

study

an

Fz

value

of

N

was

utilized

as

a

threshold

of

probable

-LRB-

spinal

-RRB-

column

injury

which

is

in

the

range

of

the

published

head

impact

loads

in

cadaver

studies

A

value

of

N

m

was

used

as

the

threshold

for

probable

column

injury

for

interpretation

of

My

readings

from

the

lower

neck

sensor

In

reality

the

true

axial

compressive

failure

load

of

the

human

cervical

spine

is

likely

slightly

lower

than

that

measured

by

the

head

input

loads

in

cadaver

tests

-LRB-

due

to

inertial

effects

of

the

cadaver

head

-RRB-

yet

substantially

greater

than

the

lower

cervical

spine

force

data

reported

in

the

same

cadaver

tests

Thus

the

real

world

relevance

of

threshold

values

used

for

both

PII

and

probable

column

injury

as

a

predictor

of

human

injury

risk

must

be

tempered

consistent

with

the

known

biofidelity

limitations

of

the

ATD

neck

-LRB-

described

previously

-RRB-

and

the

wide

variation

in

injury

tolerance

of

the

human

spine

as

described

below

The

biomechanical

literature

suggests

that

the

tolerance

of

the

human

cervical

spine

to

serious

injury

is

influenced

by

several

mechanical

factors

including

individual

tolerance

variations

due

to

age

and

gender

load

magnitude

and

loading

rate

pre-alignment

-LRB-

initial

head-to-neck

position

-RRB-

and

end

conditions

of

the

cervical

spine

Pintar

et

al.

reported

that

serious

-LRB-

AIS

-RRB-

cervical

spine

injury

under

axial

compression

loading

conditions

occurred

at

N

with

a

loading

rate

of

m/s

-LRB-

for

a

female

cadaver

-RRB-

and

N

with

a

loading

rate

of

m/s

-LRB-

for

a

male

cadaver

-RRB-

In

the

present

study

of

the

near-side

driver

ATD

sensors

recorded

upper

neck

Fz

values

exceeding

even

N

neck

compression

and

only

one

far-side

passenger

dummy

-LRB-

Test

-RRB-

exceeded

a

neck

sensor

reading

of

N

compression

Controlling

for

loading

rate

age

and

gender

in

a

sample

of

human

cadaver

head-neck

compression

tests

Pintar

and

reported

that

compressive

tolerance

varied

from

kN

in

the

young

-LRB-

third

decade

-RRB-

to

kN

in

the

very

old

-LRB-

ninth

decade

-RRB-

Failure

loads

-LRB-

recorded

at

the

lower

cervical

spine

-RRB-

ranged

from

kN

at

quasi-static

loading

rates

to

kN

at

dynamic

loading

rates

-LRB-

m/s

-RRB-

Failure

tolerance

for

the

male

population

was

higher

than

the

female

population

-LRB-

without

regard

to

age

and

rate

of

loading

-RRB-

The

present

study

recorded

roof

rail-to-dummy

head

contacts

in

the

range

of

m/s

-LRB-

mph

-RRB-

in

the

first

ground

strike

of

the

SUV

rollovers

Thus

the

roof

rail-to-head

impact

speeds

in

the

present

study

were

within

the

range

of

loading

rates

to

cadaver

and

Hybrid

III

ATD

heads

in

the

studies

by

Pintar

et

al.

Pre-alignment

of

the

head

and

neck

complex

when

struck

by

-LRB-

or

when

it

strikes

-RRB-

the

roof

is

a

key

variable

in

determining

whether

catastrophic

injury

will

occur

and

if

so

the

specific

type

of

injury

that

will

be

sustained

Published

biomechanical

studies

suggest

that

cervical

spine

pre-flexion

yields

a

greater

incidence

of

lower

cervical

compression

and

burst

fractures

than

neutrally

positioned

spines

Restrained

occupants

in

rollover

collisions

are

typically

pre-flexed

due

to

the

initial

locking

of

their

belt

restraint

system

and

thus

are

at

higher

risk

of

cervical

spine

injury

in

the

presence

of

an

intruding

roof

structure

when

compared

to

unrestrained

occupants

This

higher

risk

of

roof

impact

for

restrained

vs.

unrestrained

occupants

in

rollovers

was

confirmed

with

U.S.

field

accident

data

The

degree

of

pre-flexion

of

the

ATD

necks

prior

to

head-to-roof

contact

in

the

present

study

was

not

determined

because

the

onboard

cameras

were

positioned

behind

the

ATDs

during

the

rollover

tests

The

seat

belt

load

cells

-LRB-

i.e.

excluding

the

two

sensors

described

previously

that

malfunctioned

-RRB-

recorded

continuous

tensile

loads

in

both

lap

and

shoulder

belts

throughout

the

test

interval

for

both

driver

and

passenger

ATDs

in

all

three

tests

This

belt

load

data

indicated

that

the

lap

shoulder

belts

locked

and

remained

locked

during

the

first

ms

test

interval

for

all

ATDs

in

all

three

tests

Nightingale

et

al.

reported

on

the

influence

of

boundary

or

end

conditions

of

the

cervical

spine

relative

to

specific

injury

types

When

the

head

was

unconstrained

and

free

to

translate

and/or

rotate

away

from

the

applied

load

no

cervical

injury

was

sustained

despite

high

input

loads

to

the

head

In

full

constraint

conditions

with

the

head

pre-flexed

along

its

stiffest

axis

-LRB-

i.e.

the

removal

of

the

normal

cervical

lordosis

-RRB-

buckling

and

burst

fractures

were

noted

With

rotational

constraint

-LRB-

e.g.

when

the

neck

flexes

forward

to

the

point

where

the

chin

is

against

the

sternum

-RRB-

bilateral

locked

facets

typically

occurred

Using

cadaver

spine

specimens

Pintar

et

al.

determined

that

the

average

peak

My

magnitude

resulting

in

major

neck

injury

was

N

m

at

the

specific

site

of

injury

in

the

cervical

spine

-LRB-

i.e.

not

positioned

as

inferior

as

the

lower

neck

load

cell

of

the

Hybrid

III

ATDs

in

the

present

study

-RRB-

The

peak

axial

head

impact

force

ranged

from

to

N

with

the

peak

flexion

bending

moment

at

the

injured

level

ranging

from

to

N

m.

Thus

the

degree

of

constraint

imposed

by

the

contacting

surface

such

as

an

intruding

roof

can

be

a

major

determinant

for

cervical

spine

injury

In

all

three

tests

of

the

present

study

the

far-side

passenger

ATDs

recorded

lower

neck

flexion

-LRB-

My

-RRB-

loads

that

exceeded

N

m.

of

the

near-side

driver

ATD

lower

neck

sensors

recorded

peak

My

loads

exceeding

N

m.

No

dynamic

test

data

for

cervical

spine

tolerance

in

lateral

bending

was

identified

therefore

no

interpretation

of

the

peak

Mx

sensor

outputs

for

any

of

the

ATDs

was

made

The

biomechanical

impact

environment

to

which

the

restrained

ATDs

were

subjected

in

the

present

study

was

shown

to

be

comparable

to

that

of

published

cadaver

studies

on

the

basis

of

the

following

head

impact

load

magnitude

and

direction

loading

rate

pre-alignment

of

the

ATD

head

and

neck

and

degree

of

rotational

head

constraint

Thus

a

comparison

of

the

ATD

sensor

outputs

for

upper

load

cell

Fz

and

lower

load

cell

My

values

to

probable

column

injury

values

of

N

and

N

m

respectively

appears

scientifically

reasonable

subject

to

the

limitations

described

above

Roof

Crush

as

a

Correlate

or

Cause

of

Injury

Two

opposing

views

exist

in

the

published

literature

regarding

whether

roof

crush

causes

serious

injury

or

whether

it

is

simply

associated

or

correlated

with

serious

injury

One

group

of

investigators

has

concluded

that

restrained

occupants

receive

catastrophic

head

and

neck

injury

from

diving

into

the

roof

and

making

head-to-roof

contact

while

the

top

of

the

vehicle/roof

is

striking/hitting

the

ground

during

a

rollover

Other

investigators

have

concluded

that

serious

neck

injuries

to

restrained

occupants

are

directly

caused

by

the

dynamic

intrusion

of

the

roof

structure

into

the

occupant

's

survival

space

during

a

rollover

crash

The

present

study

reports

quantitative

evidence

of

the

temporal

relationship

between

dynamic

roof

deformation

lap

shoulder

seat

belt

loads

and

restrained

ATD

neck

loads

which

provides

further

clarification

in

this

scientific

debate

Objective

roof/pillar

deformation

occurred

prior

to

the

occurrence

of

Peak

neck

loads

-LRB-

Fz

My

Mx

-RRB-

for

both

driver

and

passenger

ATDs

in

all

three

rollover

tests

Prior

to

the

occurrence

of

Peak

neck

loads

the

driver

and

passenger

ATD

heads

contacted

the

roof

one

or

more

times

in

all

three

tests

the

magnitude

of

neck

sensor

responses

ranged

from

to

of

the

respective

dummies

Peak

neck

loads

Thus

the

restrained

driver

and

passenger

ATDs

did

indeed

dive

into

the

roof

while

the

roof

was

in

contact

with

the

ground

resulting

in

Local

Maximum

neck

load

values

which

in

no

instance

exceeded

of

the

Absolute

Maximum

-LRB-

Peak

-RRB-

neck

load

In

particular

the

diving

neck

loads

-LRB-

Local

Maxima

-RRB-

for

the

far-side

passenger

ATDs

were

only

of

the

Peak

neck

loads

-LRB-

Fz

and

My

-RRB-

for

all

three

tests

-LRB-

Table

Fig.

-RRB-

In

each

test

the

Peak

neck

loads

of

the

far-side

passenger

ATD

occurred

within

ms

following

the

time

of

maximum

objective

roof

crush

for

all

three

tests

which

is

consistent

with

published

inertial

effects

of

the

ATD

head

in

transmitting

an

axial

force

to

the

lower

neck

sensors

In

contrast

Peak

neck

loads

for

the

near-side

driver

ATD

occurred

up

to

ms

following

the

time

of

occurrence

of

objective

roof

crush

for

all

three

tests

The

onboard

cameras

also

revealed

observable

roof

crush

into

the

far-side

versus

the

near-side

occupant

compartment

during

the

time

of

the

peak

neck

loads

which

was

completely

consistent

with

the

timing

and

higher

neck

load

magnitudes

of

the

passenger

compared

to

driver

ATD

for

all

three

tests

The

lap

and

shoulder

belt

load

profiles

for

both

driver

and

passenger

ATDs

provide

further

insights

in

the

scientific

debate

regarding

roof

crush

as

a

correlate

versus

a

cause

of

serious

injury

During

the

time

interval

of

the

Peak

neck

loads

in

the

passenger

ATDs

for

all

three

tests

the

shoulder

belt

load

which

should

increase

in

magnitude

as

it

resists

torso

augmentation

instead

consistently

decreased

by

to

only

N

in

some

cases

The

lap

belt

showed

the

same

reduction

in

load

during

the

time

period

that

Peak

neck

load

was

recorded

it

was

reduced

by

to

approximately

N

-LRB-

Table

Figs.

and

-RRB-

The

belt

load

reductions

occurred

at

the

same

time

that

on-board

cameras

clearly

recorded

the

passenger

ATD

hanging

upside

down

in

the

lap

shoulder

belt

and

the

roof

crushing

into

the

occupant

space

This

time

of

observable

roof

crush

also

occurred

contemporaneously

with

the

objective

roof

crush

predicted

by

the

accelerometers

mounted

on

the

SUV

roof

rails

The

belt

load

that

was

recorded

during

each

Peak

neck

load

event

for

the

far-side

passenger

ATD

was

less

than

of

the

Peak

belt

load

in

all

three

tests

-LRB-

Table

-RRB-

The

shoulder

and

lap

belt

load

cells

indicated

that

the

belts

were

off-loaded

-LRB-

i.e.

loading

decreased

-RRB-

as

the

roof

crushed

down

on

the

ATD

head

and

pushed

the

ATD

back

toward

the

seat

cushion

away

from

the

shoulder

and

lap

belts

at

the

time

of

Peak

neck

loads

-LRB-

Fig.

-RRB-

Additionally

the

deformation

of

the

passenger

-LRB-

far-side

-RRB-

B-pillar

lowered

the

upper

attachment

point

-LRB-

i.e.

D-ring

-RRB-

for

the

belt

causing

slack

in

the

shoulder

belt

with

a

concomitant

reduction

in

shoulder

belt

load

Figure

shoulder

and

lap

belts

are

off

loaded

-LRB-

i.e.

load

decreases

-RRB-

as

the

roof

crushes

down

on

the

passenger

head

and

pushes

the

dummy

back

toward

the

seat

cushion

away

from

the

shoulder

and

lap

belts

at

the

time

of

injurious

neck

loads

Repeatability

and

Reliability

The

FMVSS

dolly

rollover

test

methodology

has

been

criticized

for

its

alleged

lack

of

reliability

and/or

repeatability

The

results

of

this

study

however

demonstrated

that

the

rollover

tests

are

very

reliable

when

viewed

from

a

vehicle-based

occupant

protection

frame

of

reference

Test-to-test

comparisons

of

the

FMVSS

rollover

results

revealed

remarkable

similarity

in

predicting

the

time

of

occurrence

of

Peak

neck

loads

for

both

driver

and

passenger

ATDs

The

Peak

neck

Fz

occurred

in

all

three

tests

at

ms

for

the

driver

ATD

-LRB-

Fig.

and

Table

-RRB-

and

ms

for

the

passenger

ATD

-LRB-

Table

-RRB-

The

Peak

neck

My

occurred

in

all

three

tests

at

ms

for

the

driver

ATD

-LRB-

Fig.

and

Table

-RRB-

and

ms

for

the

passenger

ATD

-LRB-

Table

-RRB-

The

Peak

value

for

Mx

occurred

in

all

three

tests

at

ms

for

the

driver

ATD

and

ms

for

the

passenger

ATD

These

small

variations

in

time

of

occurrence

of

roof/pillar

deformation

and

Peak

neck

loads

are

particularly

remarkable

given

that

-LRB-

-RRB-

the

data

came

from

six

different

dummies

and

three

different

vehicles

tested

on

three

different

days

-LRB-

-RRB-

the

differences

in

the

time

of

occurrence

of

the

Peak

neck

loads

was

ms

in

an

overall

time

interval

of

ms

and

-LRB-

-RRB-

each

ms

time

interval

included

either

a

sampling

rate

of

data

points

-LRB-

and

-RRB-

or

-LRB-

-RRB-

Figure

absolute

maximum

value

for

upper

neck

Fz

occurred

in

all

three

tests

at

ms

for

the

driver

dummyFigure

absolute

maximum

value

for

lower

neck

My

occurred

in

all

three

tests

at

ms

for

the

driver

dummy

Quantitative

analyses

were

undertaken

to

determine

the

significance

probability

of

each

pairwise

comparison

Restated

the

probability

that

the

similarity

of

the

maximum

and

minimum

values

of

any

two

tests

were

related

to

something

other

than

chance

was

analyzed

-LRB-

e.g.

vs.

vs.

and

vs.

-RRB-

Appendix

examines

this

issue

and

computes

the

probability

for

each

pair

of

test

metrics

This

analysis

revealed

that

there

is

a

probability

that

the

differences

in

time

occurrence

of

Peak

neck

loads

between

these

results

are

NOT

due

to

random

chance

alone

Stated

more

simply

there

is

a

less

than

probability

that

these

differences

are

coincidental

Validity

The

constellation

of

driver

vs.

passenger

neck

loads

measured

in

this

test

series

of

SUV

rollovers

was

consistent

with

certain

incidence

trends

of

catastrophic

head

and

neck

injuries

observed

in

real-world

rollovers

with

restrained

front

seat

occupants

of

the

peak

neck

loads

recorded

in

the

near-side

driver

ATD

neck

sensors

exceeded

the

threshold

values

for

probable

column

injury

which

were

used

in

this

study

In

contrast

the

far-side

passenger

ATDs

recorded

Peak

neck

loads

that

consistently

exceeded

the

threshold

for

probable

column

injury

due

to

neck

flexion

My

These

findings

are

consistent

with

data

obtained

from

NHTSAs

National

Accident

Sampling

System

-LRB-

NASS

-RRB-

database

which

showed

serious

spinal

injuries

were

more

frequent

for

the

far-side

occupants

-LRB-

compared

to

the

near-side

-RRB-

where

the

source

was

most

often

coded

as

roof

windshield

and

interior

A

probability

of

two

common

catastrophic

spinal

column

injuries

was

predicted

by

the

passenger

ATD

neck

sensors

in

all

three

rollover

tests

A

combination

load

of

compression

and

of

flexion

is

associated

with

burst

fractures

and

wedge

compression

fractures

This

load

profile

was

recorded

by

the

upper

and

lower

neck

sensors

in

the

far-side

passenger

ATD

in

Bilateral

facet

dislocation

injuries

have

been

associated

with

sagittal

plane

flexion

The

flexion

moments

recorded

by

the

passenger

ATD

lower

neck

sensors

in

tests

and

exceeded

the

threshold

values

for

probable

spinal

column

injury

by

Thus

the

results

of

this

rollover

test

series

suggest

that

the

FMVSS

dolly

rollover

test

may

be

a

valid

predictor

of

serious

spinal

injuries

to

restrained

occupants

in

real-world

rollovers

The

results

of

this

study

provide

a

unique

data

set

that

furthers

understanding

of

probable

spinal

column

injury

mechanisms

within

a

rollover

crash

environment

Such

information

may

assist

the

scientific

community

and

automotive

engineers

in

recommending

and

designing

appropriate

intervention

strategies

to

mitigate

morbidity

and

mortality

in

rollover

crashes

Moreover

these

data

may

inform

government

agencies

in

formulating

appropriate

public

safety

policy

to

improve

rollover

crash

protection

for

restrained

occupants

Conclusions

During

each

of

the

three

FMVSS

dolly

rollover

tests

of

Ford

Explorer

SUVs

the

far-side

passenger

ATDs

exhibited

Peak

neck

compression

and

flexion

loads

which

indicated

a

probable

spinal

column

injury

in

all

three

tests

In

those

same

tests

the

near-side

driver

ATD

neck

loads

never

predicted

a

serious

injury

In

all

three

tests

objective

roof/pillar

deformation

occurred

prior

to

the

occurrence

of

Peak

neck

loads

-LRB-

Fz

My

-RRB-

for

far-side

passenger

ATDs

and

Peak

neck

loads

were

predictive

of

probable

spinal

column

injury

The

production

lap

and

shoulder

seat

belts

in

the

SUVs

which

restrained

both

driver

and

passenger

ATDs

consistently

allowed

ATD

head

contact

with

the

roof

while

the

roof

was

contacting

the

ground

during

this

ms

test

series

Local

peak

neck

forces

and

moments

were

noted

each

time

the

far-side

passenger

ATD

head

contacted

-LRB-

dived

into

-RRB-

the

roof

while

the

roof

was

in

contact

with

the

ground

however

the

magnitude

of

these

local

maxima

was

only

of

Peak

neck

loads

in

all

three

tests

Diving-type

neck

loads

were

not

predictive

of

spinal

column

injury

for

either

driver

or

passenger

ATD

in

any

of

the

three

tests

When

viewed

from

a

vehicle-based

occupant

protection

frame

of

reference

the

existing

FMVSS

dynamic

rollover

test

is

a

repeatable

reliable

and

valid

test

method

to

evaluate

the

risk

of

probable

spinal

column

injury

in

rollover

crash

environments

O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O B I O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O 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An outwardly rectifying anionic background current in atrial myocytes from the human heart This report describes a hitherto unreported anionic background current from human atrial cardiomyocytes . Under whole-cell patch-clamp with anion-selective conditions , an outwardly rectifying anion current -LRB- IANION -RRB- was observed , which was larger with iodide than nitrate , and with nitrate than chloride as charge carrier . In contrast with a previously identified background anionic current from small mammal cardiomyocytes , IANION was not augmented by the pyrethroid tefluthrin -LRB- 10 μM -RRB- ; neither was it inhibited by hyperosmolar external solution nor by DIDS -LRB- 200 μM -RRB- ; thus IANION was not due to basal activity of volume-sensitive anion channels . IANION was partially inhibited by the Cl − channel blockers NPPB -LRB- 50 μM -RRB- and Gly H-101 -LRB- 30 μM -RRB- . Incorporation of IANION into a human atrial action potential -LRB- AP -RRB- simulation led to depression of the AP plateau , accompanied by alterations to plateau inward calcium current , and to AP shortening at 50 % but not 90 % of complete repolarization , demonstrating that IANION can influence the human atrial AP profile . The electrophysiological behaviour of cardiac myocytes from mammalian hearts is determined by the combined activity of a range of different cation and anion channel types . The reversal potential for chloride -LRB- Cl − -RRB- ions in the heart -LRB- ECl -RRB- lies between ∼ − 60 and − 40 mV -LSB- 1 -RSB- . Negative to ECl outward Cl − movement generates depolarizing ionic current , whilst positive to ECl inward Cl − movement generates repolarizing ionic current . Therefore , the activation of Cl − channels can influence both the resting membrane potential and the duration of cardiac action potentials -LRB- APs -RRB- -LRB- -LSB- 1 -- 3 -RSB- for reviews -RRB- . Several different anion channel types have been identified that may contribute to cardiac physiology and pathophysiology -LSB- 1 -- 3 -RSB- . Of the cardiac anion channel currents thus far identified , the three major types are : -LRB- i -RRB- a cystic fibrosis transmembrane conductance regulator -LRB- CFTR -RRB- current-activated through cAMP-dependent phosphorylation -LRB- ICl , cAMP ; e.g. -LSB- 4 -- 6 -RSB- -RRB- ; -LRB- ii -RRB- a stretch - or swelling-activated Cl − current -LRB- ICl , Swell ; e.g. -LSB- 7 -- 9 -RSB- -RRB- and -LRB- iii -RRB- a Ca2 + - activated Cl − current -LRB- ICl , Ca ; e.g. -LSB- 10 -- 12 -RSB- -RRB- . Recently , an outwardly rectifying anionic background current -LRB- IAB -RRB- has been identified in cardiac myocytes from two commonly studied model species -LRB- rat and guinea-pig -RRB- using whole-cell patch-clamp measurements -LSB- 13,14 -RSB- . IAB is distinct from previously identified Cl − currents as it has a distinct permeability sequence and is insensitive to the stilbene diphosphonate Cl − channel inhibitor DIDS , to cell swelling and to intracellular Ca2 + and cAMP -LSB- 13,14 -RSB- . IAB can also be differentiated from other major cardiac anion currents as it can be activated by the pyrethroid agent tefluthrin -LSB- 14 -RSB- . Anion substitution experiments have provided evidence that IAB can influence AP duration -LRB- APD -RRB- -LSB- 13 -RSB- . There is some disagreement as to whether or not a basally active anionic current exists in human atrium -LSB- 15,16 -RSB- and there is no information as to whether humans exhibit an IAB with the characteristics of that seen in small mammal hearts . Therefore , the present study was undertaken to determine whether or not IAB exists in adult human cardiac myocytes . The resulting findings indicate the presence in human atrial myocytes of an outwardly rectifying anionic background current -LRB- IANION -RRB- . Notably , the IANION observed in this study has the potential to contribute to human atrial electrophysiology , but is distinct from both the IAB recorded previously from myocytes from small mammal hearts -LSB- 13,14 -RSB- and from outwardly rectifying stilbene diphosphonate-sensitive anionic currents recorded previously from human atrium -LSB- 17 -RSB- . Methods Atrial myocyte isolation The study was approved by the local Central and South Bristol Research Ethics Committee and was conducted in accordance with the principles of the Declaration of Helsinki . Human right atrial appendages were obtained , with consent , from 32 patients -LRB- 27 males , 5 females , average age 69.7 ± 1.7 years -RRB- undergoing coronary artery bypass surgery . Single human atrial myocytes were isolated from right atrial appendages by mechanical and enzymatic dispersion . Tissue samples were quickly immersed in cardioplegic solution -LRB- see Table 1 ; solution G , 100 % O2 , ice cold -RRB- . The samples were chopped into small chunks and washed with an EGTA-containing solution -LRB- see Table 1 ; solution H -RRB- gassed with 100 % O2 for 15 min at 37 °C . The chunks were then incubated in the same solution from which EGTA was excluded and protease type XXIV -LRB- 3 U/ml , Sigma -RRB- and collagenase type V -LRB- 250 U/ml , Sigma -RRB- were added . The medium was continuously gassed with 100 % O2 at 37 °C . After 15 min , the incubation medium was substituted for the same solution containing collagenase only . Myocytes were progressively released from the chunks into the supernatant and their yield monitored under a microscope . The suspension was washed in enzyme-free solution and the myocytes were stored at room temperature until use -LRB- within ∼ 8 h of cell isolation -RRB- . Electrophysiology Solutions used . Experimental solutions for the investigation of anionic current were similar to those used previously to study IAB -LSB- 14 -RSB- ; the composition of all solutions used is given in Table 1 . Osmolarity values given for each of the solutions listed in Table 1 were measured using a micro-osmometer employing a freezing-point method -LRB- Advanced Instruments , Norwood , MA , USA -RRB- . Myocytes used in whole-cell voltage-clamp experiments were superfused -LRB- 20 -- 25 °C -RRB- with a standard Hepes-buffered Tyrode 's solution -LRB- see Table 1 ; solution A -RRB- until the whole-cell recording configuration had been obtained . For isolation of background anion current , sodium-free Tyrode 's solutions were used -LRB- solutions B -- E -RRB- in which Na was replaced by N-methyl-d-glucamine -LRB- NMDG -RRB- , with one of several possible dominant anions : solution B , chloride ; solution C , aspartate ; solution D , iodide ; solution E , nitrate . All drugs used were added to solution E from stock solutions made in dimethyl sulfoxide -LRB- DMSO -RRB- with an exception of N - -LRB- 2-naphthalenyl -RRB- - -LRB- -LRB- 3,5-dibromo-2,4-dihydroxyphenyl -RRB- methylene -RRB- glycine hydrazide -LRB- Gly H-101 -RRB- , which was solved in distilled water . The hyperosmotic external solution -LRB- solution F -RRB- was prepared by adding 70 mM sucrose to solution E . A Cs-based pipette solution -LRB- solution I -RRB- was used for all experiments . Solution I was sodium-free to prevent contamination of chloride currents by the sodium -- calcium exchanger current . Drugs . Diisothiocyanostilbene-2,2 ′ - disulfonic acid -LRB- DIDS , final concentration 200 μM -RRB- , 5-nitro-2 - -LRB- 3-phenylpropylamino -RRB- benzoic acid -LRB- NPPB , final concentration 50 μM -RRB- and tefluthrin -LRB- TEF , final concentration 10 μM -RRB- were purchased from Sigma Chemical Co. -LRB- Poole , UK -RRB- . N - -LRB- 2-naphthalenyl -RRB- - -LRB- -LRB- 3,5-dibromo-2,4-dihydroxyphenyl -RRB- methylene -RRB- glycine hydrazide -LRB- Gly H-101 , final concentrations of 10 and 30 μM -RRB- was purchased from Merck -LRB- Frankfurt , Germany -RRB- . All the drug-containing solutions were protected from light throughout . Electrophysiological recording In electrophysiological experiments , junction potential changes were minimized by immersing the reference Ag/AgCl electrode in a 3 M KCl solution with a continuous agar bridge -LRB- 4 % agar in 3 M KCl -RRB- . Borosilicate glass pipettes -LRB- Harvard Apparatus , UK -RRB- were pulled using a vertical two-step Narishige PP-830 microelectrode puller -LRB- Narishige , Japan -RRB- and had a tip resistance of 5 -- 7 MΩ when filled with the pipette solution . During anion substitution experiments , background anion current was elicited from voltage-clamped myocytes -LRB- superfused with solutions B , C , D and E in the whole-cell configuration -RRB- by depolarizing ramps from − 90 to +70 mV from a holding potential of − 50 mV -LRB- ramp rate of 0.32 V s − 1 ; sweep duration 1.03 s -RRB- . A holding potential of − 50 mV was used to inactivate the Na + - current and T-type Ca2 + - current . Recordings were made using an Axopatch 200A amplifier , and data were recorded on computer using pClamp v. 9.0 software -LRB- Axon Instruments , Forster City , CA -RRB- . Data were analyzed using the Clampfit program of pClamp v. 9.0 . Mean values of averaged original signals over five command pulses were used for statistical analysis . Hyperpolarizing voltage steps of − 20 mV and 5 ms duration were applied at 20 Hz to record the capacitance transients required for direct integration and the calculation of cell capacitance . The statistical significance between control and the drug periods or and other anions were determined by the Paired Student 's t-test using either Microsoft Excel or GraphPad Prism v. 4.0 . The statistical significance between the normal and hyperosmotic solutions was calculated with two-way ANOVA test using GraphPad Prism v. 4.0 . Statistical significance was considered to refer to the 95 % level of confidence -LRB- p < 0.05 -RRB- . Human atrial action potential simulations The Courtemanche et al. human atrial action potential -LRB- AP -RRB- model -LSB- 18 -RSB- was modified to incorporate a formulation for IANION based on the experimental data obtained with and Cl − in Figs. 1 and 2 . Readers are referred to -LSB- 18 -RSB- for the general equations required to set up the model . The following equation was used to simulate anionic background current -LRB- IANION -RRB- where EANION represents the current reversal potential and gANION is the conductance of IANION . By fitting Eq . -LRB- 1 -RRB- to experimental data shown in Fig. 1B and scaled to the mean data shown in Fig. 2A , we obtained gANION = 0.37 pS/pF , EANION = − 45.64 mV , c = 0.87 , d = 8.4 × 10 − 4 mV − 1 for the - sensitive IANION , and gANION = 0.19 pS/pF , c = 0.94 , d = 2.5 × 10 − 4 mV − 1 for the Cl − - sensitive IANION . Results and discussion The voltage protocol used for these experiments was similar to that used previously to study IAB present in cardiomyocytes from small mammal hearts -LSB- 14 -RSB- and is shown as an inset to Fig. 1A . From a holding potential of − 50 mV , ascending voltage ramps were applied between − 90 and +70 mV . This protocol was applied to cells superfused first with aspartate -LRB- Asp -RRB- - containing solution -LRB- solution C -RRB- and then with different superfusates containing more permeant anions . Fig. 1A shows an example of the net current traces obtained from a cell superfused serially with solutions containing Asp − , Cl − , and I − . Both inward and , particularly , outward current components were greater with Cl − , and I − than with Asp − in the external superfusate . Fig. 1B shows current traces for the same cell , obtained by subtracting the current in Asp − from that with each of the more permeant anions . With each of Cl − , and I − , the Asp − - sensitive difference current showed marked outward rectification . Fig. 1C compares the mean outward current amplitude at +60 mV -LRB- normalized to membrane capacitance -RRB- for the three anions . Compared to , the observed current was significantly greater with I − and smaller with Cl − as charge carrier . These observations support the presence in human atrial cells of a basally active , anionic current -LRB- IANION -RRB- ; however , the relative current amplitudes with the three permeant anions differ from those observed previously with for the IAB observed in myocytes from guinea-pig and rat hearts , where IAB was largest with -LRB- permeability sequence ; -LSB- 13,14 -RSB- -RRB- . Fig. 2A shows the mean IANION -- voltage relation for 19 atrial cells , with as the major external anion -LRB- with IANION measured as the − Asp − difference current -RRB- . The mean current -- voltage relation for the resulting current showed clear outward rectification , with an observed reversal potential -LRB- Erev -RRB- for IANION in these experiments of − 45.7 ± 2.2 mV -LRB- obtained by pooling Erev values from individual experiments -RRB- . Previous studies provide evidence that human atrial cells exhibit ICl , Swell -LRB- e.g. -LSB- 15,17,19 -- 21 -RSB- -RRB- . Therefore , in order to determine whether or not IANION could be attributed to basal activity of channels mediating ICl , Swell , Asp − to substitutions were also made using hyperosmolar external solution -LSB- 14 -RSB- . The mean data from eight such experiments are shown in Fig. 2B . There was no statistically significant difference between the plotted densities of IANION from the I -- V relation obtained in hyperosmolar solution and that shown in Fig. 2A , suggesting that IANION is distinct from ICl , Swell . In order to characterize further IANION from human atrial myocytes , the sensitivity of the current to a range of pharmacological interventions was tested . Fig. 2C summarises the effects of the various interventions -LRB- expressed as % changes in - sensitive current at +60 mV -RRB- . The stilbene disulphonate DIDS failed to inhibit IANION at a concentration -LRB- 200 μM -RRB- that would be anticipated to inhibit ICl , Swell -LSB- 19,21 -RSB- . On the other hand , tefluthrin -LRB- 10 μM -RRB- , which we have previously reported to activate the IAB seen in myocytes from guinea-pig hearts -LSB- 14 -RSB- , failed to alter significantly the amplitude of IANION from human atrial myocytes . Together with the relative IANION amplitudes in I − , Cl − and , the lack of effect of tefluthrin indicates that IANION is distinct from the previously reported rat/guinea-pig IAB -LSB- 13,14 -RSB- . Moreover , the lack of significant inhibition of the current by DIDS or hyperosmolar solution makes the IANION observed in the present study distinct from ICl , Swell -LSB- 1 -RSB- and from an osmolarity - and stilbene-sensitive outwardly rectifying chloride current recently reported by Demion and colleagues -LSB- 17 -RSB- . NPPB -LRB- 50 μM -RRB- produced a partial , statistically significant -LRB- p < 0.05 -RRB- inhibition of IANION . The glycine hydrazide Cl − channel inhibitor Gly H-101 failed to produce a significant blockade of IANION at 10 μM -LRB- ∼ 7-fold greater than the reported IC50 for CFTR channel inhibition at +60 mV -LSB- 22 -RSB- -RRB- ; but produced partial attenuation of the current at 30 μM -LRB- ∼ 20-fold the reported IC50 for CFTR -LSB- 22 -RSB- -RRB- . Evidence for the presence of CFTR -LRB- ICa , cAMP -RRB- in human atrial cells is mixed -LSB- 1,15,19 -- 21,23 -RSB- , with a number of studies failing to observe the current in response to β-adrenergic stimulation , forskolin or cAMP -LRB- e.g. -LSB- 15,19 -- 21 -RSB- -RRB- . Previous work has failed to find evidence for ICl , Ca in human atrial myocytes -LSB- 24 -RSB- and , moreover , the presence of EGTA in the pipette dialysate -LRB- Table 1 , solution I -RRB- and external -LSB- Ca2 + -RSB- replacement in our experiments would have inhibited any -LSB- Ca2 + -RSB- i-activated conductances on membrane depolarization . Therefore , the IANION seen here appears to differ not only from guinea-pig and rat IAB -LSB- 13,14 -RSB- but also from the three major reported cardiac anion conductances in : -LRB- i -RRB- being basally active and -LRB- ii -RRB- its overall pharmacological profile and sensitivity to anion substitution . In order to gain insight into the physiological role of IANION , the current was incorporated into human atrial AP simulations as outlined in the ` Methods ' . Fig. 3A shows the simulated APs -LRB- at an AP frequency of 1 Hz -RRB- from the Courtemanche et al. model -LSB- 18 -RSB- both without -LRB- Control -RRB- and with inclusion of IANION , whilst Fig. 3B shows the corresponding current profiles during the time-course of the AP . With either and Cl − as charge carrier , incorporation of IANION into the model produced shortening of AP duration at 50 % repolarization -LRB- APD50 ; the measured APD50 values were 184 , 165 and 159 ms for Control , Cl-sensitive IANION and NO3-sensitive IANION , respectively -RRB- . In contrast , APD90 was comparatively unaffected -LRB- the measured APD90 was ∼ 305 ms under each condition -RRB- and resting potential also changed relatively little -LRB- with resting potential values of − 81 , − 79 and − 78 mV , respectively , for Control , IANION with Cl − and IANION with -RRB- . The more marked effect of IANION inclusion at less negative potentials during AP repolarization is concordant with the outwardly rectifying nature of the current . An additional observation made from the AP simulations is that incorporation of IANION also influenced the profile of L-type calcium current -LRB- ICa , L -RRB- during the AP plateau : the initial rapid component of ICa , L was unaffected by IANION incorporation , but the sustained component during the AP plateau showed a modest reduction . Thus , both an increase in repolarizing current carried by IANION and the consequent decrease in the sustained component of ICa , L combined to lead to AP plateau depression and abbreviation of APD50 . The results shown in Fig. 3 demonstrate clearly that IANION is able to influence human atrial AP repolarization . Further work is now warranted to determine both the extent to which the incorporation/omission of IANION influences the susceptibility of human atrial cells and tissue to arrhythmia and to pursue the underlying identity and regulation of this novel background conductance .

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O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B B O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O

action potential
anion
anionic
atrium
atrial myocyte
background current
cardiac
heart