Ok After First Aid Comes the Accident Reconstruction You left me a lot of clues on how the events went down BASIS PRELIMINARIES FOR SUCCESSFUL ACCIDENT INVESTIGATION • Be a “Columbo” • Thin 5 “Ws” (Who, What, When, Where & Why) and “H” (How) • Key Mission - Investigate • Key Result – Document Evidence After the police • The second type of investigator that arrives on the scene, including insurance adjusters, private investigators, and accident reconstructionists, can still gather much useful evidence. Even though some evidence might be gone, other evidence can be gathered and used together with the police measurements and at-scene photographs to determine what happened. • Types of evidence that can be gathered include the location of pre-impact skid marks, offset marks and gouge marks. If gathered properly, these can help the accident reconstructionist to determine the pre-impact direction and speeds of the vehicles, the types of evasive action used by the drivers and ultimately who was at fault in the accident. PHOTOGRAPHY ACCIDENT SCENES a. Overall of scene b. Facing direction of vehicles approach c. Area of impact d. Fixed object damage e. Sight distances f. Sight Obstructions g. Road Condition h. Any evidence which you are about to secure i. points of rest of vehicles, objects, people ii. tire marks iii. metal scars iv. debris v. fluid marks i. Any other conditions or items that may be of importance The NOW Picture not the after WHAT TO DO AT THE SCENE • BE SAFE! • Coordinate with claims adjuster • Talk to driver • Inspect the scene • Inspect vehicles and other damaged property • Secure evidence • Talk to police not at the police • Talk to witnesses • Detail on-site claims activity Safety does quit because you have traffic vest on • “Safety First” is the phrase that needs to occupy the thoughts of the investigator the entire time the investigation is being done. Even though this slows down the investigation, obviously it is a necessary component to being available for the next assignment. Though the scope of this paper is not to show methods to follow when conducting a scene investigation in a safe manner, it is a reminder to use proper safety methods. Remember the investigator is out there to gather evidence and not to cause another accident. When arriving at the scene be sure to park completely off of the roadway and as far off the shoulder as possible. Be visible with proper safety equipment, including safety vests and always be thinking “Safety First”. Blood borne pathogens are present • Once at the scene and after remembering “Safety First”, size up the scene and decide what needs to be logged and preserved. The physical evidence can be extremely helpful in assisting the accident reconstructionist in his job. This evidence includes pre-impact skid marks, which will show the direction of travel and assist in determining the speeds of the vehicles and offset skid marks and gouge marks, which help to show where the impact occurred. Other useful information includes scratch marks, oil or fluid spills, which can be helpful in determining the vehicles final rest positions. When using conservation of linear momentum calculations to determine vehicle speeds, the impact and departure angles and distances are necessary. Look Left Look Right Look all the way around the Scene ELEMENTS OF AN ACCIDENT (CHAIN OF EVENTS) Common events are: 1. Point of possible perception B where a normally attentive person could have perceived the hazardous situation. Always comes at or before the 6. First Harmful Event B “the first occurrence in a point of perception. traffic accident that results in appreciable damage or injury; the occurrence determining 2. Point of perception B where the (potentially) the time and place of the accident; usually the hazardous situation is actually perceived by the first contact in impact.” driver or pedestrian involved. 7. Initial contact B the first accidental touching of an object collided with by a traffic unit in motion. 3. Encroachment B is movement into the path assigned to another traffic unit. Example: crossing 8. Maximum engagement B the greatest collapse the centerline. or overlap in a collision. The deepest penetration of the perimeter of the traffic unit. 4. Start of evasive action B the first action taken by a traffic unit to avoid a collision course or otherwise 9. Disengagement B separation of a traffic unit in avoid a hazard. motion from an object with which it has collided. 5. Point of no escape B that place and time beyond Note: May have repeated contacts where #7, #8, which the accident cannot be prevented by the and #9 are repeated in the second collision. traffic unit. The position of this point in the chain of events can vary considerably. 10. Stopping and final position B where the vehicles come to rest; the accident situation is stabilized. FOUR BASIC ELEMENTS OF ACCIDENT INVESTIGATION • Geometric and Traffic Regulatory Clues – Geometric deficiencies – Surface deficiencies – Signing location and deficiencies – Detail traffic control operations – Street lighting location and deficiencies – Construction zones – Sight distances – Sight obstructions That Scene Has a Little Box that Tells an Amazing Story ANATOMY OF AN ACCIDENT Phase 1: Pre-Impact • Ability to Make Appropriate Decision • Perception / Reaction (Conspicuity) • Attempt to Avoid • Attempt to Stop ANATOMY OF AN ACCIDENT Phase 2: Impact • Damage • Injury • Speed and Direction Changes • “Crash Worthiness” of Objects ANATOMY OF AN ACCIDENT Phase 3: Post-Impact • Movement of Vehicle to Point of Rest • Occupant Movements / Additional Injury • Vehicle / Occupant “Containment” Ok look at the Crush and Mush FOUR BASIC ELEMENTS OF ACCIDENT INVESTIGATION • Scene Clues – Skid marks – Gouge marks – Points of impact – Debris – Fixed object locations and damage PHOTOGRAPHY VEHICLES a. Basic 4 of each unit b. close ups of areas of damage to each unit c. Interior i. Seats ii. Dashboard iii. Gearshift iv. important items (alcohol, drugs, etc.) Look around again and again and again Things you would do: WHY ? 1. Examine the tyres of the vehicles Flat or damaged tyres may cause the car to lose control 2. Examine the road’s condition Oil spill, strange obstacles and sharp objects may cause the accident 3. Record the features of the skid marks May show whether the tire was flat or overloading. 4. Measure the length of the skid marks May help estimate the speed of the vehicle before impact. 5. To know whether the drivers are drunk or Alcohol or drug will affect a driver’s reaction time medicated during an accident. 6. Obtain the oral confession of the eyewitnesses They can provide information which are helpful in reconstructing the accident. 7. Examine the hazard lights of the Vehicle To check out whether the victim had turned on the hazard lights before the collision. 19 Look at DON’T TOUCH THE GLASS Air-Size-Tread-Scuff Marks-Stock- After Market METAL SCARS Characteristics How They Are Made Accident Significance A. Scratch 1. Narrow 1. With little pressure 1. Shows where a vehicle rolled 2. Sheet metal dragged across over on the roadway road surface 2. Shows the path the vehicle followed B. Scrape 1. Broad 1. With little pressure 1. Locating point of maximum 2. Underbody parts engagement C. Chip Gouge 1. A small and deep chunk of 1. By metal parts with the force 1. Made during maximum pavement dug out of road of an accident behind it Engagement surface 2. Not just weight alone 2. Can not determine movement or direction of vehicle travel D. Chop Gouge 1. Broad & shallow 1. Vehicle frames 1. Occurs at maximum 2. Heavy mark in bituminous 2. Transmission housing engagement material 3. Bent wheels 2. It can indicate the direction of 3. Only a scratch in Portland 4. Any metal part that is broad in travel cement (concrete) shape and size E. Groove Gouge 1. Long 1. By projecting 1. Can/can not determine 2. Narrow a. nuts direction of travel b. studs 2. Continues beyond point of c. etc. maximum engagement 2. Drive Shaft 3. Can match it with the vehicle part making it 3. Broken tie rod ends F. Towing Scratches & Grooves Same as A, B & E above 1. Towing a vehicle from the 1. None scene 2. Can add confusion to the investigation 3. Should observe when vehicles are being moved Types of Tire Marks Tire Marks Skid Yaw Tire Marks Marks Scrubs Features of skid marks 25 START and STOP The acceleration of a vehicle Acceleration = the rate of change of the speed vu a t v u 2a s 2 2 a = acceleration; v = final velocity; u = initial velocity; t = time interval; s = distance travelled 26 Take our your drag sled do the math To prove F = constant x W PULL F Figure 2 Figure 1 W 27 F W Drag factor f = F / W 28 The braking of a vehicle speed 254 D f Where speed : the speed just before sliding (measure in km/h) f : drag factor D : length of the skid mark (measure in m) 29 Skid Marks • When you brake suddenly, the wheels of your car lock. • You no longer have the ability to steer. • The car will slide straight ahead. • Skid marks are usually straight. • The skid mark provides evidence of the distance over which braking took place. ABS and Skid Marks • Anti-lock brake systems (ABS) prevent locking and skidding by turning the brakes on and off several times a second. • The driver can maintain steering control. • Vehicles equipped with ABS may leave faint, intermittent skid marks. • These skid marks may be in a curved path. Yaw Marks • Yaw marks occur when a vehicle travels in a curved path faster than the tires can handle. • The adhesion limit of the tires is reached, so they begin to slip. • Tires “squeal” and leave marks on the pavement. EXAMPLES OF SKIDS Centrifugal or Sideslid Skid Yaw Skid • Yaw marks are always curved. • There are often striations at an angle to the length of the mark. Tire Scrubs • Tire scrubs are caused by a damaged or overloaded tire. • They happen during or immediately after a collision. • Tire scrubs are usually curved and irregular in width. • They may have striations at an angle. • This picture shows a straight skid mark that changes to an irregular, curved tire scrub at impact. • The dark mark is a tire scrub from a second car. Measuring Skid Marks • If 4 marks are found, they should be measured individually. • To get the average skid distance, add the four measurements together and divide by four. Skid Marks Continued • If three skid marks are found, add the three together and divide by three. • The same applies to two marks. • If only one mark is found, measure the entire length and use this as the skid distance. Drag Factor • Tires slide on some road surfaces easier than others. • Can you think of road conditions under which tires would slide easily? What type of road surface would be the hardest for tires to slide on? Examples of Drag Factor • Asphalt: 0.50 to 0.90 • Gravel: 0.40 to 0.80 • Ice: 0.10 to 0.25 • Snow: 0.10 to 0.55 ACCIDENT MEASURING PROCEDURE I.Decide if measurements are necessary Photograph the scene II. Locate the temporary evidence III. IV.Locate and mark each point to be measured, including: a. Start of skid marks b. Skid mark direction changes c. Skid mark crossings d. Vehicle wheel positions at first rest e. Gouges in the roadway f. Major debris points V. Make a field sketch of the accident scene Math is Primary ALL THE WAY! You Have Arrived!! • You now have the three variables required to complete the minimum skid speed formula. S 30Dfn S 30Dfn In this formula: S = speed in miles per hour 30 = a constant value D = skid distance in feet f = drag factor for the road surface n = braking efficiency in decimal form TRAFFICWAY CONDITIONS THAT CAN CONTRIBUTE TO AN ACCIDENT 1. View Obstructions 5. Construction Zones - Advanced warning - On the road - Cone/barrel placement - Off the road - Equipment & crew - Roadway contours - Work zone speeds - Intersections 6. Traffic Control Signs 2. Reduced Visibility - placement - Darkness - absence - Fog/smoke - readability - Heavy snow or rain - appropriateness - Glare Traffic Signals - Visibility 3. Surface Conditions - operation sequence - Slipperiness - clearance intervals - Ruts 7. Street Lighting - Holes - Placement - Curbs - Intensity - Shoulders - Maintenance - Railroad crossing 8. Pedestrian/Bicycle - Facilities 4. Road Alignment - Sidewalks - Curves - Crosswalks - Road widths - Bridges IMPORTANT ELEMENTS IN THE FORMATION OF OPINIONS • Post accident vehicle movement • Point of impact • Skid marks /evidence of braking previous to impact • Human factors • Documents • Reference sources and materials HOW OPINIONS ARE FORMED • Statements • Measurements • Photographs • Calculations • “Standards of Knowledge” • Facility review • Operational review Drawing the Scene Roadway Evidence There are many types of roadway evidence that is left from a car wreck. A few of the most typical items are: • Paint Marks left by Police •Skid Marks •Yaw Marks •Tire Tracks •Gouges in the Pavement or Dirt •Damage to Guardrails, Barrier Walls, Telephone Poles, Curbs, Buildings, Mailboxes, and Other Structures. •Tree Scars Indicating Impact with a Tree •Fluid Stains such as Engine Oil, Transmission Fluid, Brake Fluid, Radiator Fluid, Blood, etc. •Vehicle Debris from Damaged Car Parts •Glass Fields from a Broken Windshield •Points of Impact between Vehicles •Final Resting Positions of Vehicles and Pedestrians •Clothing / Shoes Worn by Pedestrians •Cargo Separated from its Vehicle •Animals Once you have introduced yourself you can begin building rapport. Rapport can be gained with an interviewee by being relaxed and using a comfortable conversational style. Also it is important to be sincere and respectful giving the interviewee the feeling that you are understanding and can be trusted. After establishing a reasonable degree of rapport you can begin to move into the questioning phase of the interview. It is important to remember that rapport is built and maintained throughout the interview not just at the beginning. Therefore it is important to continue to be professional and somewhat relaxed during the entirety of the interview. That said, the interviewer should maintain a balance realizing the need to maintain control of the discussion and keep focused and on track. Some tips to remember before beginning: • take your time • allow periods of silence where necessary • avoid compound questions • stay neutral, professional, and unbiased • do not make assumptions or jump to conclusions • do not interrupt • questions should start out general and move to specific • try not to use leading or loaded questions • avoid accusatory questions or statements • don’t argue or debate Defects in the design or construction of a highway can create hazardous conditions that lead to accidents.