Basic Principles of Accident Reconstruction

Newton’s Laws of Motion

F=Force, M=Mass, A=Acceleration

First Law: A body will remain at rest or continue to move in a straight line at a constant speed unless acted upon by an unbalanced force, F.

Second Law: If an unbalanced force, F, acts upon a body, its center of mass will accelerate in the direction of the force. The acceleration, a, is proportional to the force, F, and the constant of proportionality, m, is called the mass of the body. F=MA

Third Law: For every force acting on a body, there is an equal and opposite force acting on something else. (For every action there is an equal and opposite reaction)

Speed Change

The best single measure of the severity of a collision is the speed change that the vehicle undergoes during the brief time interval of the collision. The speed change is the magnitude of the difference between the pre-impact and post-impact velocities of the vehicle. It occurs in a split second. In fact, a typical car collision is over in 0.12 of a second. This means that an occupant’s body and head could be jerked from 0 to 10 mph in a spilt second. Breaking it down this way makes it clear why a low speed collision can cause moderate to severe neck and back injury and pain.

The concept of the collision speed change is especially important in low speed collisions because the amount that a vehicle rebounds in a collision that results in little or no damage is significant.

In most cases, the only thing that matters to the occupant is the speed difference between his or her body and the vehicle interior.

Types of Impacts in Auto Accidents

Rear impacts

Frontal impacts

Lateral Impacts


Within each type of impact the accident reconstruction expert will try to determine:

  1. Vehicle Dynamics (the motion of bodies under the action of forces.)
  2. Occupant Kinematics (the motion of objects without reference to the forces that cause the motion.)

Vehicle Dynamics & Occupant Kinematics

Questions to occupants & witnesses to determine Vehicle Dynamics & Occupant Kinematics:

  1. Vehicle Dynamics:
  • Was your vehicle at rest?
  • If not, what was its speed?
  • Did your vehicle move as a result of the impact?
  • How far?
  • Were you behind another vehicle?
  • How far?
  • Did you hit the vehicle in front?
  • Was the vehicle in gear?
  • Which gear?
  • Were the brakes applied?
  • How hard?
  • What was the speed of the other vehicle when it struck your vehicle?
  1. Occupant Kinematics:
  • What was your height and weight at the time of the collision?
  • Where was the seat positioned?
  • How was the seat back adjusted?
  • Was the seat belt used?
  • What type of seat belt was used and how was it adjusted?
  • Where was the head restraint adjusted?
  • What was your posture in the seat?
  • Where were you looking?
  • Did you know the impact was coming?
  • Describe what happened to your body at impact.
  • Did any portion of your body contact the vehicle interior?

The exact questions will vary from case to case, but at the end, there should be a complete description of the motion of the vehicle and occupants during the collision. 

Rear Impacts

The risk of injury in any particular incident will be dependent on many factors including:

  • Collision speed change,
  • Vehicle structural characteristics,
  • Seat and head restraint dynamic characteristics,
  • Position of head restraints,
  • Use of seat belts,
  • Occupant age,
  • Occupant sex,
  • Occupant stature,
  • Occupant posture,
  • Predisposition to injury,
  • Knowledge of impending impact.

NOTE- cost to repair the vehicle is not listed as a factor. 

Injury Mechanisms in Rear Impacts

  1. Hyperextension/Hyper-flexion Injury-“Whiplash”
  2. Occupant’s body is accelerated forward,
  3. The head gets left behind because of its inertia,
  4. The neck extends backward beyond its normal limits,
  5. Forces developed in the neck accelerate the head forward,
  6. The neck overshoots its normal position, and
  7. The neck will then flex forward.
  8. Differential Rebound Injury
    1. Occupant’s torso rebounds forward from the seat prior to the head because of seat geometry and different seat and head restraint stiffness characteristics,
    2. The neck extends backwards even if there is a head restraint positioned behind the head.
  1. Tension/Compression Injury -“Ball and Chain”

Compressive and tensile (pressed & stretched) loading can develop in the cervical spine even though the overall motion of the head and neck are within normal limits, i.e. no hyperextension/hyper-flexion (whiplash).

  1. Spinal Canal Pressure Pulse Injury

Rapid head and neck motion, even if within normal limits, can cause pressure increases that may be damaging to nerves in the neck.

  1. Cervical Facet Joint Injury

The joints in the neck that allow flexibility are a common source of pain in rear impact claims. 

Accident Reconstruction Testing & Research Has determined:

  1. Symptoms such as neck pain and headaches begin to be reported in low speed rear impacts at speed changes as low as 2½ mph.
  2. Research reveals a significant prevalence of neck injury in rear impacts with speed changes of 6 to 9 mph.
  3. Some vehicles can withstand a collision speed change of up to 8 or 9 mph and remain essentially undamaged. At this level of impact, the occupant’s acceleration is far from trivial and the collision is well above the threshold level at which symptoms such as neck pain and headache are reported.
  4. A “no-damage” collision can have a speed change of 1 mph or 8 mph. It is essential to know at which end of the range the speed change lies. Risk of injury may be virtually non-existent at the lower end, but at the upper end there is a strong potential for injury.

Vehicle repair costs are not a factor in determining the severity of an injury in a rear impact claim.

  • To find out how MartinLaw, PLLC and attorney Chuck Martin will handle your car accident case please visit the car accident page.

Car Accident Causes PTSD in Children

  • Our client was driving with her two boys ages 6 and 4 in the back in carseats down a busy thoroughfare in Bellevue when a vehicle suddenly pulled out from a shopping mall exit directly in front of them.
  • She was traveling about 25 to 30 mph and had no time to stop before crashing head-on into the other vehicle.
  • This was a severe impact as the airbags deployed and the vehicles were totaled.
  • She began having persistent neck and back pain and stiffness. She sought treatment with her primary care provider.
  • She was diagnosed with cervical and lumbar strain and referred for physical and massage therapy.
  • The initial evaluation noted that she was unable to carry her other young son age 1½ for longer than 5 minutes.
  • It was also noted that she experienced left hip pain when walking and generalized aching pain across the scapulae and cervical musculature with tenderness and spasms from L3-L5. Every time she took a step with her left leg it caused a sharp pain in her left hip.
  • Additionally, she was having difficulty performing her job duties in her language translation business.
  • She continued her treatment for approximately 5 months during which time she suffered pain as a result of this accident.
  • The boys suffered mental distress as a result of the accident. A traumatic event like this is very disturbing to a young child.
  • Due to the boys’ ongoing symptoms and fear of riding in a car, or that the car was driving too fast, their mom sought assistance from a child psychologist.
  • Both boys were diagnosed with Post Traumatic Stress Disorder. The treatment consisted of the mother going to the psychologist to learn techniques to help the boys get passed their PTSD symptoms. It was felt that they were too young to get direct treatment and that going to a psychologist’s office would traumatize them further.
  • The 6 year old’s PTSD was manifested with anxiety, irritability and hypervigilance. He is constantly telling his mother or father that the vehicle is going too fast even when going slow.
  • The 4 year old’s PTSD was manfested with anxiety, irratibility, withdrawal, nightmares and difficulty sleeping.
  • The clients had a very limited amount of medical treatment.

In spite of the limited medical treatment, the law firm of MartinLaw PLLC was successful in negotiating substantial 5-figure settlements.

  • To find out how MartinLaw, PLLC and attorney Chuck Martin will handle your car accident case please visit the car accident page.


Driving Instructor Causes Car Crash

  • A driving instructor, who had a student in the vehicle with him, failed to yield right of way at 20th Avenue and Yesler, and turned left into oncoming traffic crashing head-on into our client’s vehicle.
  • Our client hit his head on the steering wheel causing a concussion and blurred vision.
  • Due to headaches and neck and lower back pain he went to the emergency room at Swedish Medical Center where it was noted that he had contusions on his forehead and left knee, acute cervical strain, lower back pain and a closed head injury.
  • He was given CT scans of the head and cervical spine which revealed head atrophy and degenerative disc disease in the cervical spine.
  • He was prescribed pain medications (Norco) and muscle relaxants (Robaxin) and discharged with diagnoses of closed head injury, acute cervical strain and acute knee contusion. He was advised to see his primary care doctor without delay.
  • He did visit his primary care doctor who prescribed physical therapy.
  • The physical therapy records note degenerative disc disease in his cervical spine, osteophyte formation in the lumbar spine, disc space narrowing at L2-3, lumbar facet arthropathy, anterolisthesis and excessive lumbar lordosis. These are medical conditions that develop over time and are not immediately caused by a traumatic injury. They would be considered preexisting conditions.
  • The physical therapist observed guarded walking and excessive eye movements to avoid cervical rotation and continually using his arms for support. Pain level is 8 out of 10. Also noted, pain can cause migraines.
  • He was unable to continue physical therapy as his wife had a stroke and he is her caregiver.

Despite that fact that our client’s medical treatment was intermittent and of short duration, and his primary diagnoses were for preexisting conditions, Chuck Martin was able to negotiate a substantial five figure settlement.

  • To find out how MartinLaw, PLLC and attorney Chuck Martin will handle your car accident case please visit the car accident page.

Runaway Truck Causes Fire & Destruction In Downtown Seattle

  • Our client, a lady in her mid-forties, was walking down James Street with her fiance in downtown Seattle heading for the Ferry Teminal with the intention of taking a scenic ferry ride across Puget Sound to Bremerton. Suddenly a large truck came careening down the hill, slammed into several parked cars causing one of the cars  to burst into flames. Several other cars then caught fire.
  • Our client ran down the hill to get away from the truck and the flames. She lost her balance and slammed into a nearby building.
  • A television news report on this accident was shown on KOMO 4 news.
  • Although mentally distraught, she decided to make the planned ferry trip to Bremerton, hoping that it would help calm her mental state. It is about a three hour round-trip. By the time she got back to Seattle she was in severe pain. She was also experiencing nausea, anxiety, vomiting, crying and an asthma attack.
  • She went to the emergency room at Northwest Medical Center. She was treated for her back pain with a narcotic injection and advised to return to the ER if she experienced increased pain.
  • The next day she did experience increased pain and returned to the Northwest Medical Center ER. She was again treated for her low back pain and instructed to follow-up with her primary care doctor.
  • She returned to the ER at Northwest Medical Center with sharp lower back pain radiating down her legs and reporting that it was painful to walk. The doctor suspected myofascial pain or possible herniated disc. She was discharged with pain medication.
  • She reported to the ER at Highland Medical Center. Her pain level was 7/10. Radiology reports indicate disc narrowing at L2-3, anterior osteophyte at L3, arterolisthesis at L2, sclerosis and hypertrophy at L3-4, L4-5 and L5-S1.
  • She was back in the ER at Northwest Medical Center a few weeks later for severe low back pain. This time she was referred to a neurosurgeon for evaluation for possible low back surgery.
  • She was finally able to get an appointment with her primary care doctor who noted leg weakness and shooting pains into the legs. She also reports that when she coughs it feels like she’s been “tazed”, pain shoots across her hips, her legs feel frozen and give out and pain shoots down both thighs. She was referred her for physical therapy.
  • Physical therapy started  about eight weeks after the accident. Her pain level was noted at 7/10. She continued with physical therapy for three months. The PT notes document the continuation of her pain, muscle spasms and radiculopathy throughout this period.
  • Although she had pre-existing lower back conditions, the records make it clear that these conditions were exacerbated by the accident.
  • She also had preexisting anxiety problems which were exacerbated by this accident with PTSD symptoms.
  • The case proved difficult as it appeared our client never had any physical contact with the truck that caused the accident, or any other object projected by the truck. We were finally able to determine through video footage and medical reports that she was struck on the ankle by an object from one of the exploding vehicles.
  • Another problem was the fact that nearly all of her diagnoses preexisted the accident.  However, we were able to show that the symptoms were exacerbated by the accident.
  • Despite the difficulties with he case we were able to recover a substantial five figure settlement for our client.
  • To find out how MartinLaw, PLLC and attorney Chuck Martin will handle your car accident case please visit the car accident page.

Motorcycle Accident Caused by “Phantom Vehicle”

  • A husband and wife were riding their motorcycle on a rural highway along the scenic Hood Canal. The husband was driving and the wife was on the back as a pasenger.
  • Suddenly a large SUV pulled out of a parking lot onto the highway directly in front of them. The husband had to lay the motorcycle down on the right side to keep from hitting the SUV head-on. They were traveling at about 45 mph.
  • The SUV then left the scene of the accident before anyone could record any identifying information.
  • The situation at the scene looked grim. One witness stated that as he ran to their aid he thought he would find two dead bodies. This witness was taking a smoking break from the nearby Farmer’s Market and saw the entire accident.
  • Ambulances were called and both husband and wife were taken to the nearest emergency room.
  • At the ER it was determined that the wife had injuries to her lower back, right wrist, right hip, right knee and right ankle. She had multiple abrassions to the right knee, leg and ankle and contusions to the abdomen and back.
  • The husband was found to have multiple rib fractures and injuries to the right scapula, chest wall, abdomen, pelvis, right shoulder, right arm, right elbow and right hip.
  • After several hours in the hospital it was determined that they were both stablized and they were discharged with instructions to seek follow-up medical with their primary care physicians.
  • It was later determined that the wife had a torn tendon in her right shoulder and a torn meniscus in her right knee.
  • She tried conservative treatment with physical therapy for several weeks but it soon became apparent that her shoulder required surgical repair.
  • She underwent shoulder surgery for the torn tendon.
  • About a month later she had arthroscopic surgery on her knee.
  • The husband continued with conservative follow-up care. Broken ribs are very painful but there is little that can be done medically to hasten recovery.
  • He suffered from these painful fractures for several weeks where even breathing can cause sharp pains.
  • Since there was no physical contact between the injured parties or their motorcycle and the SUV that caused the accident, the “Phantom Vehicle” provision became relevant.
  • Under Washington law, a “phantom vehicle” is a motor vehicle that causes bodily injury, death, or property damage to an insured but has no physical contact with the insured or the vehicle which the insured is occupying at the time of the accident. If however:
  • (a) The facts of the accident can be corroborated by competent evidence other than the testimony of the insured or any person having an underinsured motorist claim resulting from the accident; and
  • (b) The accident has been reported to the appropriate law enforcement agency within seventy-two hours of the accident; then
  • (c) Recovery can be obtained under the uninsured motorist provision of the injured party’s policy.
  • Unfortunately, the State Patrol Officer who investigated the accident did not obtain the names of any witnesses who actually saw the accident. She only recorded one name on her report, and that person was a nurse who had come to aid the injured parties, but who had not witnessed the accident.
  • However, the law firm of MartinLaw, PLLC immediately investigated the accident and located the witness who was taking a smoking break at the Farmer’s Market, and recorded his statement. This enabled the husband and wife to recover a substantial six-figure settlement from the underinsured provision of their own insurance policy. Without this effort by MartinLaw PLLC they would have recovered nothing due to the “Phantom Vehicle” provision.
  • To learn more on how the law firm of MartinLaw PLLC and attorney Chuck Martin will handle your car accident case please click on the car accident page.

Seattle Attorney In Car Accident

  • A Seattle attorney who works as an Arbitrator-Mediator,  was a restrained driver of a vehicle moving through an intersection when another vehicle entered the interscetion from his right and crashed into him broadside. This is a 4-way stop. Legally, if both cars are entering the intersection at the same time, the vehicle on the right has the right-of-way. Liability was disputed.
  • He began having neck pain shortly after the accident. He went to his primary care doctor who ordered an MRI and an EMG. He has had prior problems with his neck. The EMG focused on possible carpal tunnel syndrome and was inconclusive. The MRI showed moderate degenerative disc desease and moderate stenosis in his neck (cervical spine). It was determined that conservative treatment would be appropriate. Physical therapy was ordered.
  • Spinal stenosis is a narrowing of the open spaces within the spinal canal which puts pressure on the spinal cord and the nerves that travel through the spine. It is a condition that developes over time and not caused by an injury.
  • He continued physical therapy for several months with little relief.
  • Eight months afer the accident he was finally referred to the Orthopedics Department where another cervical MRI was done which revealed severe cervical stenosis. Surgery was recommended. My client wanted a second opinion which also recommended surgery.
  • One year after the accicent he retained MartinLaw to represent him. Our inititial evaluation was that this was going to be a difficult if not impossible case to win. Not only was liability a serious issue, but proving that the cervical stenosis was related to the accident seemed unlikely. But with his neck surgery looming it was imperative that he have legal representation for what could be a life-altering injury.
  • The surgery was performed one year and three months after the accident. He subsequently went through a prolonged and painful course of rehibilitation.
  • One year and eigtht months post-accident we bagan the process of preparing the case for possible settlement. We felt we could get passed the liability issue with statements made by the other driver that she did not see my client before entering the intersection.
  • We used a comparison study of the cervical MRI done immedicately after the accident as compared to the one eight months after the accident. This proved critical as the first MRI found “moderate” stenosis whereas the one done eight months later showed “severe” stenosis.
  • Two weeks after our demand package was sent, the insurance company called to inform us that they were offering policy limits to settle the case, a substantial six figure settlement.
  • For more information about how MartinLaw and attorney Chuck Martin will handle your car accident case, please go to the car accident page.

November Personal Injury News from Around the Web

Introducing our personal injury news report! From time to time we’ll check in on cases big and small happening both in the Seattle area and around the world. These are the ones we’ve highlighted for the month of November:

Big Payout for a Faulty Boat

Lawyers in Lee’s Summit, MO have won a $15 million personal injury case for a client who was injured when his boat exploded. Lawyers Rob Sullivan and Tim Morgan represented the plaintiff, Donald Black of Valley Park, MO. The Camden County jury found that the design of the boat’s fuel system was faulty.

Smokey Dyer, the former fire chief of Kansas City and Lee’s Summit, provided expert testimony in the case. Burn evidence showed the fuel line separated at a critical connection and a hose had worked its way loose from a metal piece. When Black turned on the bilge pump, leaked fuel in the cockpit and around the hull exploded and burned him severely. He was in the hospital for several months and racked up $1.3 million in medical bills. He sometimes was placed into a coma and his heart stopped six times. Skin grafts, reconstructive surgery, and further ongoing health risks became a reality for Black.

The defendant was a former subsidiary of Brunswick Corporation.

Fitbit Information Now Applicable in the Courtroom

A law firm in Calgary is working on the first known personal injury case that will incorporate activity data from a Fitbit device to help show the effects of an accident on their client.

Though the woman who was injured didn’t have a Fitbit at the time of the accident, but since she was a personal trainer at the time, her lawyers at McLeod Law think they have a case that her active lifestyle was severely affected by comparing Fitbit data compared to the baseline for someone of her age and profession.

Doctor’s testimony and observations of an injured person are commonly used to determine physical ability after an injury. Showing measured data over a long period of time wasn’t possible without undue commitment and time on the injured person’s part, so this technology may change common practices. On the flip side, insurers will want access to this data as well, so expect to see this information used on defendant’s cases as well.

Contact the Offices of Martin Law, PLLC for your legal guidance and support for your personal injury case. Get the justice you deserve.

Image source

Things to do in the Case of an Automobile Accident

Unfortunately, accidents do happen and preparing yourself for the steps to take after an automobile collision can only benefit you if you find yourself in that situation. Here are the steps we recommend you take in the event of an auto accident:

  1. Check yourself and others for injuries and call 911 if necessary.
  2. Call the police and insist on a police investigation. This will create an accurate report of the facts.
  3. Avoid discussing fault with the other parties involved in the accident.
  4. Get the following information from all drivers and parties before you leave the scene of the accident:
    1. Insurance information
    2. Phone numbers
    3. Addresses (important to serve notices)
  5. Get names and phone numbers of all witnesses to the accident.
  6. Take photographs of the damage to all vehicles as well as the accident scene. Keep a disposable camera in your just for this purpose. Use your phone or borrow a witness’ camera or phone if yours is broken during the accident.
  7. Describe the damage to your vehicle.
  8. Draw the scene of the accident. Show the position of vehicles and the direction of travel. Show any lights and signs. Show distances.

If you or someone you love is involved in an automobile accident, contact us to discuss your case and get the expert advice you need to seek justice.

Personal Injury News: Avoiding Pedestrian Accidents in Seattle

When you cross the street, walk to and from your office on your lunch break, or traverse Seattle’s sidewalks as you enjoy a night out on the town, just how safe are you? Whether or not you follow pedestrian traffic laws such as crossing at crosswalks instead of ‘jaywalking’, pedestrians are at risk for all kinds of injury and even death – just by walking down the street.

Luckily, ours is one of the safest national cities for pedestrians. Earlier this year, the Seattle Times reported on a study that found, “Among large U.S. cities, Seattle has the second-lowest fatality rate for pedestrians and cyclists, according to a new report … Seattle came away with the second-lowest fatality rate for pedestrians.” (Click here for a map of collisions involving pedestrians and/or bicyclists from 2007-August 2014.)

However, walkers still need to practice caution while they go about their travels throughout the city – particularly if they are elderly, as a 2011 local Crosscut article noted. More than half of the 62 traffic fatalities from 2008-2010 involved pedestrians, and the average age of the 25 pedestrian fatalities was 64.

As the numbers of people biking and/or walking to work only increase, there is more risk for personal injury and fatality. But there are ways that pedestrians in particular can improve on the safety of their commute. Here are some tips for avoiding pedestrian accidents in Seattle…

  • Follow pedestrian traffic laws. Many walkers know that vehicles and even cyclists must always yield to pedestrians. While this is certainly true, that doesn’t make it safe to assume or trust that drivers and cyclists will – or can – do so. Don’t cross the street where there is not a marked crosswalk or pedestrian crossing sign. Even then, look both ways and wait for drivers and cyclists to come to a complete stop before crossing in front of them.
  • Walk with others. Research has shown that accidents and fatalities resulting from pedestrian-car accidents are reduced in areas where there are more people walking. As you commute, choose routes with higher pedestrian traffic.
  • Be noticeable and alert. When walking at night, wear reflective and bright clothing, and if you can, carry a flashlight. Do not walk and talk on the phone or text-message – especially when crossing the street. Stay alert and take note of vehicles that seem to be speeding, allowing them to pass or stop before you cross the street in front of them.

If you or someone you love is a pedestrian involved in an accident with a car or bicyclist, please contact our offices to acquire the guidance and expertise to seek justice.

Featured photo source: Flickr.

What to do When you Get into a Bicycle Accident

Cyclists can save a lot on their monthly and annual costs by biking to work instead of driving, and it also improves their health and fitness! Seattle and the Greater Seattle areas are popular for cyclists of all levels of skill. Approximately 20 percent of Washington State residents rode a bicycle in 2001, and it is the fastest growing mode of transportation in our region, according to the Cascade Bicycle Club.

The Seattle Department of Transportation reports that more than 158,000 Seattleites ride bikes – either for general recreation or to get to a destination (such as work). Seattle is ranked number two in the nation for urban walking and bicycling, as the Seattle Times reported this spring. However, hundreds of bicycle collisions still happen each year – more than 1,800 accidents involving a cyclist were reported between 2007-2011. Click here for more bicycling safety statistics.

Cyclists of all skill levels need to be alert, follow traffic and safety laws, and know their rights to avoid and protect themselves from car accidents and the repercussions.

Here are the important steps to follow when you get into a bicycle accident – particularly if it’s an accident involving another motor vehicle:

  1. Call the police. If you are able, call the police immediately after the bike accident and wait for them to arrive. If the police are involved, you can be sure that correct contact information will be exchanged. Additionally, the police will write an accident report so that there is documentation of the incident – you may need this later, to press insurance claims. Make sure to report all personal injuries even if they seem to be minor – after an accident, adrenaline in your body may trick you into thinking you are uninjured, so be aware. If there were any witnesses to the accident, it is helpful to also have them report what they saw or heard.
  2. Exchange information. Of course, you should get the contact information for everyone involved in the accident – the driver of the car(s), and any witnesses. For any vehicles involved, obtain the driver’s name, insurance information, phone number, home address, and driver’s license number. You should also get the contact information for any witnesses to the bicycle accident.
  3. Contact a Personal Injury Attorney. Before you contact the insurance companies, you should find and choose a personal injury attorney to help you with your case. These kinds of lawyers are skilled in this kind of situation, to ensure you receive the fullest extent of just compensation for damages to yourself, your bike, and future costs associated with the accident. If you talk to an insurance company before speaking to a lawyer, you may not receive the full recompense you are eligible for under the law.

Click here for some more tips on handling bicycle accidents with cars, according to a blog at Should you get into a bicycle accident with a car, contact Martin Law, PLLC for excellent, skillful support and guidance through the after-accident process.

Featured photo credit Flickr user Fort Greene Focus.