Presented to:Presented to:Committee for the Study of a Motor Committee for the Study of a Motor

Vehicle Rollover Rating SystemVehicle Rollover Rating SystemMay, 29 2001May, 29 2001

Collection of NASS CDS Data Relating to Rollover

Robert Woodill – Veridian EngineeringJohn Brophy – NHTSA

NASS CDS Rollover VariablesNASS CDS Rollover Variables

A rollover is defined as any vehicle rotation of 90 degrees or more about any true longitudinal or lateral axis.

The variables also attempt to identify:• What initiated the rollover• At what plane of the vehicle exterior the tripping force was applied and• The direction of the initial roll.

NASS CDS Rollover Variables NASS CDS Rollover Variables (continued)(continued)

CDS Data Collection Screen

NASS CDS Rollover Variables NASS CDS Rollover Variables (continued)(continued)

Rollover Data:•Type•Quarter Turns

Rollover Initiation:•Type•Location•Object Contacted Class•Object Contacted

Rollover Specifics:•Location on Vehicle Where Initial Tripping Force Applied•Direction of Initial Roll

NASS CDS Rollover Variables NASS CDS Rollover Variables (continued)(continued)

Element Attributes:•Trip‑over•Flip‑over•Turn‑over (justify)•Climb‑over•Fall‑over•Bounce‑over

•Collision with

another vehicle•Other rollover initiation type (specify):•Unknown•End-over-end

NASS CDS Rollover Variables NASS CDS Rollover Variables (continued)(continued)

Element Attributes (continued)

•Most Popular One is the:

Cherry Turn-Over:

NASS CDS Rollover Variables NASS CDS Rollover Variables (continued)(continued)

Source for coding rollover variables in CDS NASS:

Researcher determined — primary sources are the scene and vehicle inspections. Secondary sources are photographs, police report, driver interviews, and other interviewees.

Trip-OverTrip-Over

Example 1: Vehicle lateral motion is resisted by opposing force (curb) at wheels, inducing roll moment.

Trip-Over Trip-Over (continued)(continued)

Example 2: Vehicle lateral motion is resisted by opposing force (surface friction)at wheels, inducing roll moment. Tire side wall breaks down and rim gouges usually occur.

RightRight RightRight Rear Rear FrontFront

Trip-Over Trip-Over (continued)(continued)Example 3: Vehicle lateral motion is resisted by opposing force (surface friction)at wheels, inducing roll moment. Wheelsdig into soft soil causing trip.

Trip-Over Trip-Over (continued)(continued)

Example 4: Vehicle lateral motion is resisted by opposing force (surface friction) at wheels, inducing roll moment. Incline helps cause side wall to break down and rim to dig in causing trip.

RightRight RightRight Rear Rear FrontFront

LeftLeft Left Left FrontFront RearRear

GuardrailTaper

Flip-OverFlip-OverExample 1: Forward moving vehicle is vigorously rotated about its longitudinal axis by a ramp like object such as a guard rail taper.

Flip-Over Flip-Over (continued)(continued)

Example 1: Forward moving vehicle is vigorously rotated about its longitudinal axis by a ramp-like object such as a steep embankment.

Turn-OverTurn-Over

Centrifugal forces from a sharply turning or rotating vehicle produce a rollover moment when resisted by surface friction

No Gouges, and NoRight Side Rim Damage

Turn-OverTurn-Over ??

Roof & Left Roof & Left Side Side

DamageDamage

Left Side Wheel DamageLeft Side Wheel Damage

Left Rear Wheel DamageLeft Rear Wheel Damage

Turn-Over or Trip-OverTurn-Over or Trip-Over

• Heavier damage to right side of roof indicates that the left side was probably leading.

• Damage to left side wheels verifies that the left side was leading and that it is a Trip-Over rather than a turn-over.

Climb-OverClimb-Over

Vehicle climbs up and over a fixed object such as a barrier or guardrail

Fall-OverFall-Over

Vehicle is tipped by slope so that its center of gravity is outboard of its wheels.

Fall-Over?Fall-Over?

Fall-Over or Trip-Over?Fall-Over or Trip-Over?

Left Side Wheel DamageLeft Side Wheel Damage

Close-up LF Wheel DamageClose-up LF Wheel Damage

Fall-Over or Trip-Over?Fall-Over or Trip-Over?

• Note left side wheel damage• Indicates that the left side was leading• Verifies that this is a trip-over rather

than a fall-over

Bounce-OverBounce-Over

Vehicle rebounds off fixed object (such as a guardrail), and overturns as a consequence

Instead of rebounding, the vehicle climbs over the fixed object (such as a guardrail), and overturns on the opposite side

However, IfHowever, If

It becomes a?Climb-Over

Impact With Another Impact With Another VehicleVehicle

Rollover is the immediate result of an impact with another vehicle.

Momentum from the impact causes vehicle to turn-over, no tripping is involved

Vehicle Impact Vehicle Impact or or

Trip-OverTrip-Over

RightRight Right RightRearRear Front Front

Left Side Roll DamageLeft Side Roll Damage

Roll and LR Wheel DamageRoll and LR Wheel Damage

Roll and LF Wheel DamageRoll and LF Wheel Damage

Left FrontLeft Front Left RearLeft Rear

Vehicle Impact or Trip-OverVehicle Impact or Trip-Over

• Vehicle/vehicle impact was the impetus to send this vehicle into curb but,

• The curb impact was the initiator for the rollover and thus this is a TRIP-OVER.

Tripped or Untripped?Tripped or Untripped?

Left FrontLeft Front Left RearLeft Rear

ConclusionConclusion

• Scrutiny of both scene evidence and vehicle damage -- especially the wheels is critical.

• Close-up images of the wheels are very important.

QuestionsQuestions