Accident Investigation

Tree eats car…

Car in the bush…

Truck in house…

Sand buckets work…

Possible cause for single vehicle accidents

Possible Reasons 1.*Distraction (Phone, Radio, Bugs…) 2.Drunk 3.Excessive speed with loss of control 4.Slick road surface (unsafe speed, unsafe distance, bald tires) 5.Avoidance of animal, person or other vehicle 6.Brake/Accelerator Confusion 7.Equipment malfunction 8.Asleep

Process Scene Photograph Draw Measure Interview Witnesses Look at vehicle documents Document weather/road conditions

Skid Marks Evidence of braking before crash Friction between road and tire causes burning Can determine Minimum Traveling Speed preceding accident, site of incident, evidence of avoidance or lack of avoidance

Skid Marks-Min. Speed S = speed in miles per hour (MPH), D = skid distance, in feet, and f = drag factor (includes grade considerations, braking efficiency, and coefficient of friction) f=Coefficient of Friction X Breaking Efficiency + slope Simplistic SKID to STOP formula: Assumes final velocity is 0 mph (ie. gently comes to a stop with no impact)

Skid Marks and Speed V i = initial velocity, in feet per second (FPS), V E = velocity at the end of skid, in feet per second (FPS), a = acceleration/deceleration, in feet per second squared, and D = skid distance, in feet. Note: Car 1 is still traveling into Car 2 when skid marks stop

Friction Table (Estimates) Concrete: 0.75 Wet Concrete: 0.60 Dry Asphalt: 0.65 Wet Asphalt: 0.50 Wet Grassy Field: 0.20 Gravel and Dirt Road: 0.35 Ice: 0.10 to 0.15 Snow: 0.20 to 0.25

Flaws with Friction Table Road varies in age, exact construction material, and condition Subject’s car tire condition important

Best ways to determine real coefficient of friction Optimal use subject car and run at known speed Create skid marks Calculate coefficient of friction Or use a Drag Box

Determining a surface’s coefficient of friction Drag Box –Box has weight –Box has tire surface on bottom of box –Measure force to pull box and maintain speed –Coefficient of friction=Avg. pull force/box weight

What if no skid marks? Explanations….

Brake malfunction –How do disk brakes work?How do disk brakes work? Not watching road Couldn’t see out window Drunk Unconscious

No Skid Marking Event Data Recorder –Logs pre-crash speed –Logs brake use

No Skid Marks Can look at Victim's Crush Depth –Depth depends on car type –About 20in for every 35mph V=(V o +k)D V=Impact Speed V o =max speed for no crush (manufacturer) K=crush stiffness (manufacturer) D=Avg. Crush Depth (measured)

Did Driver signal lane change or have headlights on?

Brake Lights

Lights Brake Lights have filament bowed upward This means lights were on at crash Heat and impact causes deformed shape Means that driver braked before crash

Lights Horizontal filaments tells of lights no being on at crash

NYS Traffic Law Speeding (1-10 MPH over posted limit): 3 points Speeding (11-20 MPH over posted limit): 4 points Speeding (21-30 MPH over posted limit): 6 points Speeding (31-40 MPH over posted limit): 8 points

NYS Traffic Law Speeding (more than 40 MPH over posted limit): 11 points Reckless driving: 5 pointsReckless driving Failing to stop for a school bus: 5 points Following too closely (tailgating): 4 points Inadequate brakes: 4 points Inadequate brakes while driving an employer's vehicle: 2 points

Failing to yield right-of-way: 3 points Violation involving a traffic signal, stop sign, or yield sign: 3 points Railroad-crossing violation: 3 points Improper passing, unsafe lane change, driving left of center, or driving in wrong direction: 3 points Leaving the scene of an incident involving property damage or injury to a domestic animal: 3 points Safety restraint violation involving a person under 16: 3 points Any other moving violation: 2 pointsmoving

May have your license suspended for accumulating 11 or more points within 18 months