Why Hikers & Bikers Should Why Hikers & Bikers Should Avoid Cars, Trucks, and Avoid Cars, Trucks, and

TrainsTrainsThe Dynamics of Trauma The Dynamics of Trauma

in Vehicle Collisions in Vehicle Collisions Involving Pedestrians or Involving Pedestrians or

BicyclistsBicyclists

Brian A. DonaldsonBrian A. Donaldson

Operations SupervisorOperations SupervisorWestern Eagle County Ambulance Western Eagle County Ambulance

DistrictDistrictEagle, ColoradoEagle, Colorado

brian@proEMSeducators.combrian@proEMSeducators.com

Revised 2005Revised 2005

Ground RulesGround Rules Please place all electronic devices Please place all electronic devices

into a quiet or vibrate mode, if into a quiet or vibrate mode, if possible.possible.

Be an active participant…you don’t Be an active participant…you don’t want to listen to me for an hour!want to listen to me for an hour!

Relax & enjoy yourself.Relax & enjoy yourself.

If you are easily offended, please If you are easily offended, please locate the exit nearest your seat. locate the exit nearest your seat.

One Final Ground RuleOne Final Ground Rule

What happens in St George…What happens in St George…

Stays in St GeorgeStays in St George

Learning ObjectivesLearning Objectives

Identify Newton’s Identify Newton’s Laws of Motion and Laws of Motion and the Conservation of the Conservation of

MomentumMomentum

Identify Estimated Identify Estimated Vehicle Striking Vehicle Striking Speed based on Speed based on Contact DamageContact Damage

Identify Probable Identify Probable Injuries based on Injuries based on Vehicle Striking Vehicle Striking

SpeedSpeed

Identify Priority Identify Priority Patients based on Patients based on Physical Findings Physical Findings

Why Should I Care?Why Should I Care?

Statistically, for each fatality, there will be four Statistically, for each fatality, there will be four serious injuries and 18 minor injuries.serious injuries and 18 minor injuries.

These collisions cost in excess of one billion These collisions cost in excess of one billion dollars annually in the United States alone.dollars annually in the United States alone.

In 2001 in the U.S. there were 45,000 bicyclists In 2001 in the U.S. there were 45,000 bicyclists injured and 728 killed.injured and 728 killed.

In 2001 in the U.S. there were 78,000 In 2001 in the U.S. there were 78,000 pedestrians injured and 4,882 killed. pedestrians injured and 4,882 killed.

What are the What are the DynamicsDynamics of of Trauma?Trauma?

Dynamics is a branch of Mechanics Dynamics is a branch of Mechanics which is a field of Physics. which is a field of Physics.

The study of Dynamics is concerned The study of Dynamics is concerned with the effects of forces on a body, with the effects of forces on a body,

especially forces that do not especially forces that do not originate within that body.originate within that body.

The Evolution of PhysicsThe Evolution of Physics

AristotleAristotle

384-322 B.C.384-322 B.C.

Greek philosopher Greek philosopher and scientistand scientist

The Evolution of PhysicsThe Evolution of Physics

GalileoGalileo

1564-16421564-1642

Italian physicist Italian physicist and astronomerand astronomer

The Evolution of PhysicsThe Evolution of Physics

Isaac NewtonIsaac Newton

1642-17271642-1727

English physicist, English physicist, mathematician, mathematician, theologist and theologist and

alchemistalchemist

Newton’s First Law of Newton’s First Law of MotionMotion

In the absence of outside forces, an In the absence of outside forces, an object at rest will remain at rest, and object at rest will remain at rest, and

an object in motion at a constant an object in motion at a constant velocity will remain in motion at an velocity will remain in motion at an unchanged velocity indefinitely. unchanged velocity indefinitely.

Newton’s Second Law of Newton’s Second Law of MotionMotion

When a force is applied to an object, When a force is applied to an object, the object is accelerated. This the object is accelerated. This

acceleration is in the direction of the acceleration is in the direction of the force and proportional to its strength, force and proportional to its strength, and is also inversely proportional to and is also inversely proportional to

the mass being moved.the mass being moved.

Newton’s Third Law of Newton’s Third Law of MotionMotion

Forces are always produced in pairs, Forces are always produced in pairs, with opposite directions, and equal with opposite directions, and equal

magnitudes. magnitudes.

Practical Application - Practical Application - MotionMotion

Pedestrian struck by a Pedestrian struck by a moving vehiclemoving vehicle

Pedestrian partially or Pedestrian partially or fully accelerated (+) to fully accelerated (+) to speed of striking vehiclespeed of striking vehicle

Pedestrian accelerated Pedestrian accelerated (-) by slide, tumble, etc(-) by slide, tumble, etc

Vehicle & pedestrian Vehicle & pedestrian both deformedboth deformed

What is Momentum?What is Momentum?

Momentum =Momentum =

Mass X Mass X VelocityVelocity

An object with An object with either large mass or either large mass or

high velocity has high velocity has great great

momentum.momentum.

Conservation of MomentumConservation of Momentum

In a collision, the total momentum of In a collision, the total momentum of the colliding objects before the the colliding objects before the collision, is equal to the total collision, is equal to the total

momentum of the objects after the momentum of the objects after the collision.collision.

Practical Application - Practical Application - MomentumMomentum

Prior to CollisionPrior to Collision

3,500 lb X 40 mph = 140,0003,500 lb X 40 mph = 140,000

185 lb X 5 mph = 925185 lb X 5 mph = 925

Total = 140,925Total = 140,925

After CollisionAfter Collision

3,500 lb X 38.15 mph = 133,5253,500 lb X 38.15 mph = 133,525

185 lb X 40 mph = 7,400185 lb X 40 mph = 7,400

Total = 140,925Total = 140,925

Why is Physics Important?Why is Physics Important?

The “Poor Bastard Rule”The “Poor Bastard Rule”

In cases of In cases of collisions collisions

between a motor between a motor vehicle and a vehicle and a pedestrian or pedestrian or bicyclist, the bicyclist, the latter shall latter shall

always lose.always lose.

Case in Point!Case in Point!

Another Case in Point!Another Case in Point!

Speed KillsSpeed Kills

Speed / Chance of DeathSpeed / Chance of Death

20 mph20 mph 5%5%

30 mph30 mph 41%41%

40 mph40 mph 84%84%

Three Phase Collision ModelThree Phase Collision Model

CarryCarry

FallFall

Slide / TumbleSlide / Tumble

The Carry PhaseThe Carry Phase

The phase during which:The phase during which:

the pedestrian or bicyclist is in initial the pedestrian or bicyclist is in initial contact with the striking vehicle.contact with the striking vehicle.

the pedestrian or bicyclist is the pedestrian or bicyclist is accelerated, or partially accelerated, accelerated, or partially accelerated,

to the striking vehicle speed.to the striking vehicle speed.

initial contact injuries occur.initial contact injuries occur.

The Fall PhaseThe Fall Phase

The phase during which:The phase during which:

the pedestrian or bicyclist breaks initial the pedestrian or bicyclist breaks initial contact with the striking vehicle.contact with the striking vehicle.

the pedestrian or bicyclist is acted upon by the pedestrian or bicyclist is acted upon by gravity and begins to return to the earth.gravity and begins to return to the earth.

(-) acceleration of the striking vehicle (-) acceleration of the striking vehicle usually begins.usually begins.

The Slide / Tumble PhaseThe Slide / Tumble Phase

The phase during which:The phase during which:

the bicyclist or pedestrian is acted upon by the bicyclist or pedestrian is acted upon by subsequently contacted objects or subsequently contacted objects or

surfaces.surfaces.

the bicyclist or pedestrian is likely to the bicyclist or pedestrian is likely to experience secondary contact with striking experience secondary contact with striking

vehicle.vehicle.

Potential for additional injuries is great.Potential for additional injuries is great.

Common Striking Vehicle Common Striking Vehicle ShapesShapes

WedgeWedge

PontoonPontoon

BluntBlunt

Common Collision Common Collision ClassificationsClassifications

WrapWrap

Forward Forward ProjectionProjection

Roof VaultRoof Vault

Fender VaultFender Vault

WrapWrap

Usually occurs with pontoon shaped vehicles and is Usually occurs with pontoon shaped vehicles and is not speed dependent.not speed dependent.

Pedestrian is bent around leading edge of vehicle Pedestrian is bent around leading edge of vehicle and may be projected forward upon vehicle (-) and may be projected forward upon vehicle (-)

acceleration.acceleration.

Pedestrian is fully accelerated to the speed of the Pedestrian is fully accelerated to the speed of the striking vehicle.striking vehicle.

Usually occurs upon direct anterior or posterior Usually occurs upon direct anterior or posterior strike.strike.

Forward ProjectionForward Projection

Usually occurs with wedge or pontoon shaped Usually occurs with wedge or pontoon shaped vehicles at speeds of 25 mph, or less, when vehicles at speeds of 25 mph, or less, when strike is above center of mass of pedestrian.strike is above center of mass of pedestrian.

May occur with blunt shaped vehicles at any May occur with blunt shaped vehicles at any speed.speed.

Pedestrian is fully accelerated to the speed of Pedestrian is fully accelerated to the speed of the striking vehicle and projected forward.the striking vehicle and projected forward.

Roof VaultRoof Vault

Usually occurs with wedge or pontoon shaped Usually occurs with wedge or pontoon shaped vehicles at speeds greater than 45 mph.vehicles at speeds greater than 45 mph.

Pedestrian usually makes secondary contact Pedestrian usually makes secondary contact with striking vehicle on upper windshield or with striking vehicle on upper windshield or

points rearward.points rearward.

Pedestrian is accelerated to only a portion of Pedestrian is accelerated to only a portion of the striking vehicle speed.the striking vehicle speed.

Fender VaultFender Vault

Usually occurs in off-center lateral strikes at Usually occurs in off-center lateral strikes at speeds of less than 45 mph.speeds of less than 45 mph.

Pedestrian may have secondary contact with Pedestrian may have secondary contact with hood, A-post, or windshield.hood, A-post, or windshield.

Pedestrian will usually break contact with Pedestrian will usually break contact with vehicle on striking side.vehicle on striking side.

Pedestrian is accelerated only to a portion of Pedestrian is accelerated only to a portion of the striking vehicle speed.the striking vehicle speed.

Less Common Less Common ClassificationsClassifications

SomersaultSomersault Pedestrian is projected into the air and Pedestrian is projected into the air and returns to earth in front of striking vehicle, returns to earth in front of striking vehicle,

usually to be struck again.usually to be struck again.

DragDrag Usually a result of second / subsequent Usually a result of second / subsequent

vehicle strikes or prone / supine vehicle strikes or prone / supine pedestrians, and always associated with pedestrians, and always associated with

significant tissue loss.significant tissue loss.

A Good Reason to Stop A Good Reason to Stop DrinkingDrinking

Estimating Initial Area of Estimating Initial Area of ImpactImpact

Look for footwear and Look for footwear and other pedestrian other pedestrian

related items farthest related items farthest from the resting from the resting

point.point.

Look for “cone of Look for “cone of debris” terminating debris” terminating very near area of very near area of

initial impact.initial impact.

Estimating Striking Speed of Estimating Striking Speed of VehicleVehicle

Method works well for Method works well for wedge and pontoon wedge and pontoon

shaped vehicles. shaped vehicles.

Must determine initial Must determine initial head strike on head strike on

vehicle.vehicle.

Accurate in Accurate in pedestrian collisions.pedestrian collisions.

Estimating Striking Speed of Estimating Striking Speed of VehicleVehicle

MPHMPH Head StrikeHead Strike<25<25 May be May be

present on present on hoodhood

25-3025-30 Base of Base of windshield or windshield or belowbelow

30-4530-45 Base to Base to middle of middle of windshieldwindshield

Estimating Striking Speed of Estimating Striking Speed of VehicleVehicle

MPHMPH Head StrikeHead Strike45-6045-60 Middle to top of Middle to top of

windshieldwindshield

6060 RoofRoof

>60>60 Rear window Rear window and points and points

rearwardrearward

Force / Injury ConsiderationsForce / Injury Considerations

Always consider multiple (+) (-) Always consider multiple (+) (-) accelerations, multiple contact accelerations, multiple contact injuries, and multiple striking injuries, and multiple striking

vehicles.vehicles.

Always consider massive (+) (-) Always consider massive (+) (-) acceleration forces and associated acceleration forces and associated

injuries to the brain, spine, solid injuries to the brain, spine, solid organs, aorta, etc. organs, aorta, etc.

Life Threats - Head to Mid-Life Threats - Head to Mid-FemurFemur

Respiratory InsultRespiratory Insult

FracturesFractures

Spinal / CNS InsultSpinal / CNS Insult

Solid Organ InjuriesSolid Organ Injuries

Impaled ObjectsImpaled Objects

Extremity InjuriesExtremity Injuries

FracturesFractures

AmputationsAmputations

De-glovingDe-gloving

TattooingTattooing

Impaled ObjectsImpaled Objects

Fractures & AmputationsFractures & Amputations

Striking vehicle Striking vehicle speeds of 14 mph or speeds of 14 mph or greater, and lower greater, and lower extremity loading, extremity loading,

expect lower expect lower extremity fractures.extremity fractures.

Fractures & AmputationsFractures & Amputations

Striking vehicle Striking vehicle speeds of 45 speeds of 45

mph or greater mph or greater expect lower expect lower

extremity extremity amputations. amputations.

Presentation SummaryPresentation Summary

Newton’s Laws of Newton’s Laws of Motion and the Motion and the Conservation of Conservation of

Momentum apply Momentum apply to patients in these to patients in these types of collisions.types of collisions.

The higher the The higher the initial head strike initial head strike

on the vehicle, the on the vehicle, the faster it was faster it was

moving when it moving when it struck the patient.struck the patient.

Presentation SummaryPresentation Summary

The larger the The larger the vehicle, or the vehicle, or the

faster it is moving faster it is moving when striking the when striking the

patient, the greater patient, the greater the energy the energy

transferred to the transferred to the patient.patient.

Avoid the Avoid the temptation to be temptation to be

distracted by distracted by extremity injuries…extremity injuries…

it’s head to mid-it’s head to mid-femur that kills.femur that kills.

Thank You …Thank You …

… … and and

Let’s Be Careful Let’s Be Careful

Out There!Out There!

QuestionsQuestions

oror

Comments?Comments?