Traffic Crash Causes & Investigation

Three Main Causes of Traffic Crashes

• The three main causes are vehicles, drivers, and roadways, with the cause being how the element relates to the accident.

Vehicle-Related Causes

• Faulty vehicle design
• Faulty tires
• Brake failure
• Steering issues
• Stuck accelerator
• Mechanical failure

Driver-Related Causes

• Condition of the driver
• Drinking
• Drug involvement
• Fatigue or falling asleep
• Illness or injury
• Obstructed view
• Traffic violations
• Inattention or distractions from cell phones, electronic equipment, radio, CD players, smoking, eating, children, animals, personal hygiene, or reading

Roadway-Related Causes

• Design flaws
• Defects such as ruts, uneven pavement, and potholes

Four Reasons for Investigation of Traffic Crashes

• Criminal prosecution as per NRS 480.360.2, law enforcement must investigate crashes on all primary and secondary highways resulting in personal injury, property damage, or death, and gather evidence to prosecute any person guilty of any violation of the law contributing to the crash.
• Civil liability is when traffic crash information will be used to settle property damage and injury claims, and the investigating officer may be called to testify in civil trials or depositions.
• Public service is traffic crash investigation which is required by law.
• Improve traffic and vehicle safety is when crash data from reports is used by OTS, State Data Collection, and the Department of Traffic to discover trends in vehicle or highway design deficiencies.

Elements of a Traffic Crash

• Unplanned event
• Involving a motor vehicle or an object set in motion by a motor vehicle
• Occurring in transport
• Taking place on a highway
• Resulting in damage

Three Classifications of Traffic Crashes

• Property damage
• Injury
• Death

Thirteen Steps in Crash Investigation

• The steps do not necessarily have to be done in exact order, can be done case by case.

Get to the Scene Safely

• Plan the route and drive at a pace within safe abilities
• Use available information and driving proportional to the crash severity
• Being involved in a crash while responding diverts resources
• Consider requesting ambulances, fire crew, tow trucks, and additional police units.

Establish Initial Traffic Control

• First officer on-scene's responsibility
• Don't park in the crash scene, position vehicle to maximize safety and visibility to other drivers
• Assess if you need additional units
• Use overhead lights, headlights, and spotlights to illuminate the crash scene at night
• Block the scene to protect personnel and prevent evidence destruction.
• Per NRS 484B.700, authorized emergency vehicles or official vehicles of a regulatory agency may park or stand without regard to the provisions of NRS Chapters 484A through 484E inclusive, if using a warning lamp.

Caring for Injured and Involved Parties

• Deal with hazards that may cause injuries
• Handle injuries according to priority, starting with the most serious
• Use First Responder Training and give first aid if needed
• Notify dispatch of injuries and circumstances, and request special equipment
• If the crash involves a fatality or serious injury, notify the proper crash investigation to get them on the scene.

Completing Traffic Control and (PIC) Point of Intersection Control

• The main objective is to prevent additional crashes and protect involved persons
• Utilize flares and traffic cones
• Considerations:
  • Visibility: additional units on a curve
  • Weather: snowy or ice-covered roadway will require more warning and personnel
• Road configuration: multi-lane highway, re-routing traffic (alternate routes)
• Lighting: Traffic cones in the daytime, flares at night
• Flares burn at 2000 degrees and have a body, striker cap, striker plate and anti-roll devices
• NDOT can provide long-term traffic control, large traffic cones, and alternate routes
• Point of Intersection Control is manual traffic control at an intersection or roadway
• Purpose of point intersection control:
  • Restore safe and efficient movement of vehicle and pedestrian traffic
  • Safety of the public

When performing intersection control remember it is our responsibility to

• Regulating traffic flow
• Controlling turning movements
• Coordinating vehicle movements with the flow of adjacent intersections
• Detouring traffic as necessary
• Controlling pedestrian movements
• Arranging for the removal of traffic obstructions
• Facilitating emergency vehicle movements
• Rendering aid and assistance
• Equipment needed: traffic safety vest, whistle, and flashlight
• Assume responsibility for traffic control and not presume motorists will understand where to drive without signals.
• Hand signals should be clear and concise at shoulder height so motorists and pedestrians can see them easily
• Stopping traffic: extend arm and index finger towards the person to be stopped.
• To have traffic move forward: extend arm and index finger toward the person to be started.
• Flowing traffic: Left arm parallel to the ground (palm up), moved upward from the elbow to behind your head.
• Left or right turn: point index finger in the direction you want the person to go.
• Whistle: one long blast - stop signal, 2 short blasts - go signal
• Flashlight: swing the beam of light across the path of oncoming traffic
• Explain directions if a driver or pedestrian doesn't understand them
• Traffic should not flow in any one direction for more than 3 minutes if there is opposing traffic stopped and waiting.
• Stop the traffic to your left and traffic in front of you first, then stop the remaining traffic lanes.
• Always use a logical traffic flow and let left turn lanes begin their turning movement first.

Locating Drivers and Witnesses

• Identify drivers, passengers, and third-party witnesses and separate everyone before interviews
• Get a verbal statement from each person and take notes for comparison with written statements
• Be compassionate and understanding
• Ask straight forward, open-ended questions.
• Look for signs of intoxication, fatigue, or anger, get written statements, and avoid expressing your thoughts on what occurred
• Written statement should be signed
• Compare written statements, and ask follow-up questions as necessary
• Identifying passengers: information for the report, seating location in the vehicle
• Unique circumstances: request another officer respond to the hospital to obtain a statement and information from transported people Sometimes you will have a passenger, or another person present at the crash scene who will falsely claim that they were the one driving.

Photographing the Crash Scene

• Photographs: picture for those who weren't on scene, crucial when testifying
• If unsure, take photos
• The Cardinal Rule for Crash Investigation: It’s better to have information that you don’t need than to need information that you don’t have.
• Mandatory photographs:
  • Fatal accidents, Injury accidents
  • Commercial and government vehicles
  • High profile accidents involving celebrities, politicians, state officials, law enforcement
• Minimum photographs:
  • Initial lines of approach from drivers’ perspectives
  • Area of impact
  • Departure from the area of impact
  • Visible traffic control devices
  • View obstructions
  • Roadway characteristics
  • Roadway marks
  • Vehicles (8 pictures per vehicle: 4 sides and 4 corners)
  • Close-ups of exterior vehicle damage
  • Interior damage (blood, airbags, seatbelts, glass damage)
  • Injuries of occupants
• Evidence types: short lived, temporary, or permanent and whether it needs to be documented before it is gone
  • Short-lived evidence: extrication, roadway marks in rain or snow
  • Temporary evidence: construction zones, view obstructions, skid marks
  • Permanent evidence: gauges in the pavement, damage to the vehicles

Examining Crash Vehicles

• Begin with a systematic external examination: location of the damage, magnitude
• Contact damage: deformation or defacement from direct pressure
• Direct damage
• Transfer: material from one surface transferring to another
• Imprints: dents pressed into the vehicle by a stronger object
• Induced damage: damage to a vehicle other than contact damage that includes crumpling, distortion, bending and breaking
• Examine each vehicle individually and compare damage areas
• Lamps: determine if specific lights were on or off at the time of collision
• Fragile, short-lived evidence
• Do not disturb lamps or switches, turning on damaged lamps could destroy evidence This is being seen less and less because most new vehicles are equipped with HID headlights which is a not a bulb, but a mixture of gases that create the light.
• Examine the car interior: blood, dash board damage, interior glass, headliners, seat back positions, airbag deployment, seatbelt positions

Examine Roadway/Roadside Marks and Conditions

• Debris, roadway marks and defects and field sketches/diagramming
• Ability to identify and interpret evidence
• Debris material scattered with light and heavy debris
• Light debris is light solid material such as dust, dirt, mud or snow
• It will normally travel in the same direction as the vehicle from which it originated.
• Small vehicle parts are often subject to movement from their original point of rest by passing vehicles, emergency response personnel and bystanders
• Cargo also scatters widely and is often subject to movement from its original point of rest by passing vehicles, emergency response personnel and bystanders.
• Fluid spills spilled, spattered or trailing on the pavement after a fluid container is ruptured from collision
• Spatter is the collection of marks on a roadway surface made by liquid from a vehicle
• Characteristics of spatter are dark wet spots irregular in shape and surrounded by many smaller spots or “freckles”.
• Fluid trail drains from a vehicle in motion after a container ruptures.
  • Can be used to locate the path of the vehicle from the area of impact to position of rest.
• Fluid run-off occurs after a puddle of liquid accumulates beneath a vehicle and runs off in the direction of the grade present
• Fluid tracking tire prints created when a tire moves through liquid debris
• Heavy debris consists of large vehicle parts
• Roadway Marks: Tire Marks and Pavement Scars
• Tire Marks are any roadway mark which originated from a vehicle tire
• Skid Marks, Scuff Marks and Collision Scrubs

Skid Marks are a tire friction mark made by a tire that is sliding without rotation on a paved surface

• Locked Wheel Skid Marks - curved due to either the grade or super elevation (crown) of a roadway May be curved due to either the grade or super elevation (crown) of a roadway upon which the vehicle is skidding or steering input by an ABS equipped vehicle.
• Impending Skid Mark is a Very faint skid mark which indicates the transition from maximum effective braking to the beginning of a locked wheel skid
• Superimposed Skid Mark is when Made by the rear tires of a vehicle are placed directly over the skid marks made by the front tires
• Skip Skid Mark - A braking skid mark interrupted at frequent regular intervals; the skid mark made by a bouncing wheel on which brakes keep the wheel from turning
• Gap Skid Mark is from release and re-application of brakes or where the braking mark is terminated by the release of brakes before collision
• Erasure Skid Mark - A locked wheel skid where the tire slides across a smooth, hard, dirty surface creating a discernable path or pattern through the dirt
• Squeegee Skid Mark A skid on a wet, paved surface where the tire pushes moisture to the side.
• Offset Skid Mark is an abrupt change in direction of a skid mark due to a collision
• Scuff Marks are tire friction mark made by a tire that is both rotating and slipping on a paved surface
• Sideslip (Yaw mark), Acceleration Scuff and Flat Tire Scuff.
• A sideslip or yaw mark is always curved and leaves striations which are not parallel to the direction of the mark.
• Acceleration Scuffs may look like a J (J hooks).
• Flat Tire Scuff Marks edges with very light, or no marks at all from the center portion of the tire
• Collision Scrubs are a short, usually broad skid mark or yaw mark made during engagement (impact) of a collision vehicle Pavement scars
• Scratches - A light and usually irregular pavement scar made by a sliding metal part.
• Gouges are a pavement scar made by heavy or rigid metal parts forced into the pavement causing a portion of the pavement to be removed
• A roadway requires repair Defects may be construction related. Consider speed when investigating.
• Grooves or Ruts depressions by commercial vehicles
• Holes by breaking down or loss of roadway materials.
• The washboard effect is an area of roadway with a series of ripples
• Lip is an area where two roadways surfaces come together at different elevations
• Roadway construction trenches

Clear the Crash Scene

• Complete a Vehicle Impound Form, photograph vehicles, and document additional evidence
• Special towing requirements, note any roadway marks.
• The tow company clears debris/hazardous materials, the officer is ultimately responsible

Complete the Investigation

• Part I: On-scene investigation
  • Collect/review all witness statements: Are they are complete, make sense, include correct contact information, signed, and do not conflict with the physical evidence.
  • Review all evidence at the scene and ask clarifying questions
• Part II: Follow-up investigation
  • Follow up interviews as necessary
  • Efforts to locate people for hit & run or non-contact vehicle accidents

Determine What Happened

• Decide based on physical evidence, roadway marks, vehicle damage, and statements

The Enforcement Action

• Cite the driver if a traffic offense was committed
• Per NRS 484A.660, except for felonies and mandatory arrest offenses, an officer at the scene of a traffic crash may issue a citation with reasonable and probable grounds to believe the person has committed an offense listed in NRS Chapters 482 to 484. Hydroplaning is when the water on the roadway exceeds the tire tread depth.

Complete Forms and Reports

• Final step: complete all required forms, book in all evidence, and submit your report

Collision Field Sketches and Diagrams

• Final phase of documenting evidence
• Field sketch: freehand drawing of the crash scene that shows features of the scene - used to document measurements taken at the scene.
• Measuring instruments: Roll-a-Tape, Cloth Tape, Steel Tape, and Sokkia Mapping Device Finished Diagram a computer diagramming program such as Crash Zone.
• Required when the crash involves a fatal injury, likelihood of felony charges, an incapacitating injury, hit and run, or any other crash scene the officer or command feels it necessary.
• Scales used: 1" = 10’ 1" = 20’
  • Contains: Crash Number, Date & time measurements taken
  • Name & ID # of person taking measurements
  • Name & ID # of person completing diagram
  • Equipment Used