Traffic Crash Investigation
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Questions and Answers

What is the main emphasis of the traffic crash investigation lesson?

  • Simulated traffic crashes training
  • Interviewing drivers and witnesses (correct)
  • Evidence collection and interpretation
  • Scene protection and safety precautions

    • What is the term for the initial point of impact in a traffic crash?

  • First contact (correct)
  • First harmful event
  • Un-stabilized event
  • Stabilized event

    • What is the purpose of identifying the chain of events in a traffic crash?

  • To gather information from different tire marks
  • To protect property and prevent theft at the scene
  • To determine the relative importance of the order of events (correct)
  • To identify the location of the crash event

    • What is the primary goal of protecting the scene of a traffic crash?

    <p>To prevent theft and protect property</p> Signup and view all the answers

    What is the purpose of identifying the procedures for interviewing drivers and witnesses?

    <p>To collect accurate statements from drivers and witnesses</p> Signup and view all the answers

    What is the term for the location of the crash event as defined in the MUCR?

    <p>ON</p> Signup and view all the answers

    What is a motor vehicle traffic crash?

    <p>Any motor vehicle crash that occurs on a trafficway or results in a harmful event on a trafficway</p> Signup and view all the answers

    What is the minimum requirement for a motor vehicle crash to occur?

    <p>Involvement of at least one motor vehicle in transport and at least one harmful event</p> Signup and view all the answers

    What is an un-stabilized event?

    <p>An event that originates when control is lost and terminates when control is regained</p> Signup and view all the answers

    What marks the end of an un-stabilized event?

    <p>When all persons and property are at rest</p> Signup and view all the answers

    How should crashes be located?

    <p>Based on the location where the vehicle initially left the roadway</p> Signup and view all the answers

    What is perception of the hazard?

    <p>Seeing, feeling, or hearing and understanding that the unusual or unexpected movement or condition that could be taken as a about to occur</p> Signup and view all the answers

    What is encroachment?

    <p>Movement into the path assigned to another traffic unit</p> Signup and view all the answers

    What is the start of evasive action?

    <p>The first action taken by a traffic unit to escape from a collision course or otherwise avoid a hazard</p> Signup and view all the answers

    What is the roadway?

    <p>The portion of the trafficway that is improved, designed, or ordinarily used for vehicular travel, exclusive of the shoulder</p> Signup and view all the answers

    What event takes place when one wheel of the vehicle leaves the roadway?

    <p>Leaving the roadway</p> Signup and view all the answers

    What happens when one wheel of the vehicle goes off the shoulder or climbs the curb?

    <p>Leaving the road occurs</p> Signup and view all the answers

    What is the point where the force between the traffic unit and the object is the greatest?

    <p>Maximum engagement</p> Signup and view all the answers

    When does force cease to exist between two objects in a traffic crash?

    <p>At disengagement</p> Signup and view all the answers

    What is the primary responsibility of an officer upon arriving at the scene of a traffic crash?

    <p>To make the scene safe</p> Signup and view all the answers

    Why should warning devices be placed far enough from the crash scene?

    <p>To warn oncoming traffic of the hazard ahead</p> Signup and view all the answers

    What should be done to damaged vehicles blocking the roadway?

    <p>Mark their positions for measurement and take photographs</p> Signup and view all the answers

    What is a potential problem to consider while investigating a traffic crash?

    <p>Pilferage</p> Signup and view all the answers

    What should be done to oncoming vehicles at night or in low-visibility conditions?

    <p>Warn them of the hazard ahead</p> Signup and view all the answers

    What is the final event in a traffic crash?

    <p>Stopping</p> Signup and view all the answers

    Why should the investigator be mindful of the speed limit, sight distance, and stopping distances?

    <p>To place warning devices effectively</p> Signup and view all the answers

    Why may an officer be temporarily stationed at the scene of a traffic crash?

    <p>To act as a guard until the responsible party can remove the cargo or property</p> Signup and view all the answers

    What is essential for officers to do in the initial stages of a traffic crash investigation?

    <p>Locate and identify drivers, passengers, witnesses, and other people connected to the collision</p> Signup and view all the answers

    What may be necessary when dealing with juveniles in investigations?

    <p>Parental consent or court approval</p> Signup and view all the answers

    Why may it be challenging to obtain statements from individuals involved in a traffic crash?

    <p>All of the above</p> Signup and view all the answers

    How can an investigator gain the cooperation of uncooperative people?

    <p>By informing them that providing a statement may avoid a court appearance later</p> Signup and view all the answers

    What type of people may be instructed by their employers to say nothing about the collision?

    <p>Truck, bus, or train engineers</p> Signup and view all the answers

    What is the goal when questioning or interviewing people for crash investigations?

    <p>To find out as much information as possible about the traffic crash</p> Signup and view all the answers

    What is the primary goal of the investigator during an interview?

    <p>To remain neutral and gather unbiased information</p> Signup and view all the answers

    What is the recommended approach to questioning drivers and witnesses?

    <p>Being diplomatic, understanding, and fair</p> Signup and view all the answers

    Why may it be necessary to visit hospitals or other locations?

    <p>To interview injured individuals who were transported to the hospital</p> Signup and view all the answers

    What is the purpose of asking specific and clear questions?

    <p>To get clear and specific answers</p> Signup and view all the answers

    What is essential for obtaining information from people involved in a traffic crash?

    <p>Showing empathy and understanding</p> Signup and view all the answers

    What should an investigator avoid doing during an interview?

    <p>Arguing with the driver or witness</p> Signup and view all the answers

    How would you describe finding out what a person knows about a traffic crash?

    <p>An art</p> Signup and view all the answers

    What is the term for a mark made on a surface by a rolling tire without sliding?

    <p>Imprint</p> Signup and view all the answers

    Why should an investigator avoid suggesting answers to drivers or witnesses?

    <p>Because it may influence their responses</p> Signup and view all the answers

    What is the primary goal of active listening during an interview?

    <p>To ensure understanding and clarify information</p> Signup and view all the answers

    What is the recommended approach to asking questions?

    <p>Asking open-ended questions</p> Signup and view all the answers

    What should an investigator do if they have doubts about a statement made by a driver or witness?

    <p>Ask the driver or witness to clarify the statement</p> Signup and view all the answers

    What is the term for a friction mark made by a tire that is sliding without rotation on a road or other surface?

    <p>Skid mark</p> Signup and view all the answers

    What is the term for the friction mark made by a tire that is both rotating and slipping on a road or other surface?

    <p>Scuffmark</p> Signup and view all the answers

    What is usually the composition of the black mark on a bituminous surface?

    <p>Tar or asphalt softened by friction generated heat</p> Signup and view all the answers

    What is the characteristic of a skid-mark on a soft material?

    <p>It is usually a furrow</p> Signup and view all the answers

    What is the effect of abrasive particles or loose gravel on the surface?

    <p>It causes surface scratches</p> Signup and view all the answers

    What happens to the surface of a wet road when a skidding tire passes over it?

    <p>Moisture is squeegeed from the surface</p> Signup and view all the answers

    What is a characteristic of skid-marks?

    <p>They start light and become darker</p> Signup and view all the answers

    What can cause a gap in a set of skidmarks?

    <p>All of the above</p> Signup and view all the answers

    What type of skidmark is characterized by short interruptions?

    <p>Skip skid</p> Signup and view all the answers

    What is a yawmark also known as?

    <p>All of the above</p> Signup and view all the answers

    What is the type of skidmark that is made by a rotating tire that is slipping more or less parallel to its axis?

    <p>Yawmark</p> Signup and view all the answers

    What is an acceleration scuff?

    <p>A scuffmark made when sufficient power is supplied to the driving wheels to make at least one spin or slip on the road surface</p> Signup and view all the answers

    Why is it difficult to determine the exact point where skidding begins?

    <p>Because tires can slide without leaving a visible mark, and it takes time for the wheels to stop rotating</p> Signup and view all the answers

    What is the term for the area prior to a discernible skidmark?

    <p>All of the above</p> Signup and view all the answers

    Why is it important to mark the beginning and end of skidmarks?

    <p>To document the evidence before it is destroyed</p> Signup and view all the answers

    What is the purpose of measuring and photographing skidmarks?

    <p>To determine the minimum speed of the vehicle</p> Signup and view all the answers

    What is the purpose of finding the average skidding distance?

    <p>To compensate for any variation in the braking and stopping efficiency of the brakes and tires</p> Signup and view all the answers

    Why is it important to examine the road surface from different angles?

    <p>To ensure that skidmarks are not missed</p> Signup and view all the answers

    What can be used to determine the minimum speed of a motor vehicle prior to a collision?

    <p>Skidmark evidence</p> Signup and view all the answers

    Why may an officer with specialized training be necessary in a traffic crash investigation?

    <p>If criminal charges are anticipated or other circumstances dictate</p> Signup and view all the answers

    What is the first step in determining a minimum speed of a vehicle?

    <p>Locate and measure the skidmarks</p> Signup and view all the answers

    What is the purpose of measuring the overall length of each skidmark and dividing it by two?

    <p>To adjust for the wheelbase of the vehicle</p> Signup and view all the answers

    What is the recommended test speed for conducting test skids?

    <p>20-30 miles per hour</p> Signup and view all the answers

    What is the minimum number of test skids recommended to conduct for comparison purposes?

    <p>3</p> Signup and view all the answers

    What is the formula to obtain a coefficient of friction value using test skids?

    <p>30 x D</p> Signup and view all the answers

    What is the purpose of using a drag tire or drag sled in traffic crash investigation?

    <p>To obtain a coefficient of friction value</p> Signup and view all the answers

    What should be duplicated when conducting test skids?

    <p>The road surface conditions at the time of the crash</p> Signup and view all the answers

    What should be used to determine the coefficient of friction value with the use of a drag tire or drag sled?

    <p>The formula Where f is the drag factor/coefficient of friction value, F is the average pull force in pounds, and W is the weight of the drag tire/sled in pounds</p> Signup and view all the answers

    Why is it necessary to conduct multiple drag pulls with a drag tire or drag sled?

    <p>To reduce the error in the measurement</p> Signup and view all the answers

    What should be done to the pull values obtained from multiple drag pulls with a drag tire or drag sled?

    <p>They should be averaged</p> Signup and view all the answers

    What is the purpose of using the nomograph printed on the Northwestern Traffic Template or the Institute of Police Technology and Management Traffic Template?

    <p>To obtain a coefficient of friction value using test skid variables</p> Signup and view all the answers

    What is the primary objective of the lesson plan 'Introduction to Traffic Radar'?

    <p>To discuss the basic explanation of the use of RADAR in traffic speed enforcement</p> Signup and view all the answers

    What is the term 'RADAR' an abbreviation for?

    <p>Radio Detecting and Ranging</p> Signup and view all the answers

    What is the fundamental principle that explains how radar signals are changed by reflection off a moving object?

    <p>Doppler Principle</p> Signup and view all the answers

    What is the relationship between the frequency, wave length, and speed of a radar signal?

    <p>Frequency increases as wave length decreases</p> Signup and view all the answers

    What are some of the factors that can affect radar accuracy and/or effectiveness?

    <p>Weather conditions and radar instrument calibration</p> Signup and view all the answers

    What is the primary goal of identifying the elements of the fundamental case law affecting the use of radar speed measurement and enforcement?

    <p>To understand the legal implications of radar use</p> Signup and view all the answers

    What is the requirement for the radar instrument?

    <p>It must have been in proper working condition</p> Signup and view all the answers

    Where should the radar device be used to minimize distortion of readings?

    <p>On roads with minimal traffic and no rain</p> Signup and view all the answers

    What is the purpose of the tuning forks?

    <p>To test the radar instrument's accuracy</p> Signup and view all the answers

    What is the purpose of the Tactical Use of Radar Instructor?

    <p>To explain how radar can be deployed in different scenarios</p> Signup and view all the answers

    What is an example of a Single-Lane Oncoming Single Vehicle scenario?

    <p>One vehicle traveling in the opposite direction</p> Signup and view all the answers

    What is the primary unit of measurement for frequency in a radar signal?

    <p>Cycles per second</p> Signup and view all the answers

    What is the speed of a radar signal?

    <p>186,000 miles per second</p> Signup and view all the answers

    What is the effect of relative motion on the frequency of a radar signal?

    <p>It increases the frequency</p> Signup and view all the answers

    What is the purpose of the Photo-Speed Recorder?

    <p>To measure the speed of a vehicle</p> Signup and view all the answers

    What is the term for the distance from the beginning of the peak to the end of the valley in a radar signal?

    <p>Wavelength</p> Signup and view all the answers

    What is the effect of the angle of the radar antenna on the accuracy of the target reading?

    <p>It decreases the accuracy</p> Signup and view all the answers

    What is the purpose of the high and low tuning forks in testing a radar unit?

    <p>To test the accuracy of the radar unit</p> Signup and view all the answers

    What is the primary goal of an officer when using radar equipment to detect speed?

    <p>To prove that a speed law was violated</p> Signup and view all the answers

    What is the effect of the patrol car's speed on the radar reading?

    <p>It adds to the target speed</p> Signup and view all the answers

    Study Notes

    Traffic Crash Investigation

    Definition of Motor Vehicle Traffic Crash

    • A motor vehicle crash that occurs on a trafficway or in which a harmful event occurs on a trafficway
    • Includes motor vehicle crashes and motor vehicle traffic crashes
    • To be classified as a motor vehicle crash, the following elements must be present:
      • Involvement of at least one motor vehicle in transport
      • At least one harmful event
      • The harmful event is the result of an unintentional act
      • The harmful event is not the direct result of a cataclysm
      • The crash was not initiated by an action of an aircraft or watercraft
      • The crash does not include any harmful event involving a railway vehicle in transport prior to involvement of a motor vehicle in transport

    Unstabilized Event and Stabilized Event

    • Unstabilized event: an event or set of events that originates when control is lost and terminates when control is regained
    • Stabilized event: marks the end of an unstabilized event, usually when persons and property come to final rest

    Chain of Events

    • A series of events that make up a traffic crash
    • Events may not always occur in the same order
    • Each traffic unit involved in the crash has its own chain of events
    • The chains of events for two traffic units involved in the same crash will always have one or more links or events in common

    Investigating a Traffic Crash

    • Upon arrival at the scene, make the scene safe to prevent further damage or injury
    • Identify and locate drivers, passengers, witnesses, and other people who may have a connection with the collision
    • Obtain information from people involved in the crash while they are still at the scene
    • Handle evidence and valuable belongings properly
    • Take photographs and measurements of the scene before clearing the roadway

    Interviewing Witnesses and Drivers

    • Explain who you are and what your interest is in the collision
    • Be objective, positive, and diplomatic
    • Ask specific and clear questions
    • Do not suggest answers or argue with the person being questioned
    • Be adaptable and practice good listening skills

    Tire Marks

    • Tire marks can be classified into two types: imprints and friction marks
    • Imprints are marks made on a surface by a rolling tire without sliding
    • Friction marks are made by a tire that is sliding or both rotating and slipping on a surface
    • Skid marks are friction marks made by a tire that is sliding without rotation
    • Scuffmarks are friction marks made by a tire that is both rotating and slipping### Types of Skidmarks
    • Gap skidmarks are created when brakes are pumped or the driver's foot slips off the brake pedal, resulting in short spaces between the skidmarks.
    • Skip or bounce skidmarks are caused by bouncing during braking, road bumps or holes, or collisions, and are characterized by short distances between interruptions.
    • Yawmarks are scuffmarks made by a rotating tire that is slipping parallel to its axis, also known as centrifugal skidmarks, critical speed scuffmarks, or sideslip marks.
    • Acceleration scuff is a scuffmark made when sufficient power is supplied to the driving wheels to make at least one spin or slip on the road surface.
    • Flat tire mark is a scuffmark made by an over-deflected tire with too little air pressure.

    Measuring Skidmarks

    • When measuring the length of gap skidmarks, only measure the marks themselves, excluding the spaces between them.
    • When measuring skip skids, treat them as if there were no skips, and measure the entire length of the skid from beginning to end.

    Investigating Skidmarks

    • The exact point where skidding begins is difficult to determine due to tires sliding without leaving a visible mark and the time required for the wheels to stop rotating.
    • The length of the transitional period depends on how quickly brakes are being applied.
    • Any speed calculated from skidmarks is referred to as a minimum speed.
    • The investigator must be careful in observing the evidence in the indefinite area where the brakes are applied, known as the shadow, impending skidmarks, or incipient skidmarks.

    Analyzing Skidmarks

    • The investigating officer can determine the minimum speed of a motor vehicle prior to the collision using basic speed analysis and math calculations.
    • The steps to determine minimum speed include locating and measuring skidmarks, finding the average skidding distance, determining the coefficient of friction, and finding the minimum speed.

    Determining Coefficient of Friction

    • There are numerous methods of determining the coefficient of friction, including published data on typical values for different road surfaces.
    • Test skids can be conducted to obtain a specific value for the surface in question, duplicating conditions at the time of the collision.
    • The mathematical formula to obtain a coefficient of friction value is: 30 x D, where f is the drag factor, S is the test speed, and D is the longest skid length.
    • The drag tire or drag sled method can also be used to obtain a coefficient of friction value.

    Determining Minimum Speed

    • Once the coefficient of friction and skid distance are known, the minimum speed of the vehicle at the beginning of the skid can be determined using the nomograph or mathematical formula.
    • The nomograph can be used to determine the coefficient of friction value or crash vehicle speed once the variables are known.

    Introduction to Traffic Radar

    • RADAR stands for Radio Detecting and Ranging, a device used to detect and measure the speed of distant objects by analyzing radio waves reflected from their surfaces.
    • The first traffic law was passed in 1652, prohibiting the riding or driving of horses at a gallop within city limits.
    • The first automobile speed regulation was enacted in 1912, limiting automobile speeds to 12 mph in the country and 8 mph within city limits.

    Frequency and Wave Length

    • Frequency is the number of waves transmitted in one second, usually measured in cycles per second.
    • Wavelength is the distance from the beginning of the peak to the end of the valley, with most radars operating within the X-band (10.525 billion waves per second) or K-band (24.15 billion waves per second).
    • Radar signals travel at the speed of light, 186,000 miles per second.

    Doppler Principle

    • The Doppler Principle states that relative motion causes a signal's frequency to change.
    • When objects are moving closer together, the frequency increases, and when they are moving farther apart, the frequency decreases.
    • The amount of frequency change is determined by the speed of the relative motion.

    Factors Affecting Radar Accuracy

    • Angle Effect: The angle of the radar antenna can cause an improper target reading.
    • Reflective capability: The radar unit's operation is affected by the reflective capability of targets, their position, and their actual speed.
    • Batching: The radar adds a fraction of the patrol vehicle's speed to the violator's speed.
    • Scanning Effect: The rapid swinging past a fixed object of a stationary radar antenna can produce a speed reading.
    • Panning Effect: Can occur with two antenna units when the antennas are pointed at each other, causing feedback.
    • Turn on Power Surge: Turning on the power to a unit can cause a speed reading due to the sudden surge of voltage.
    • Mirror Switching Effect: Can occur on Speed gun Eights if the operator points the unit out the back window and uses the mirror to read the display without activating the mirror switching device.
    • Patrol Speed Shadow Effect: Occurs if the beam of the radar unit attaches onto a moving object instead of the terrain.

    Basic Operations of Moving Radar

    • Target Speed = Closing Speed - Patrol Speed
    • High Doppler and Low Doppler frequencies are used to calculate the target speed.
    • Testing the unit involves activating the high and low tuning forks and holding them in front of the unit to give a target speed.

    Fundamentals of Case Law

    • The officer must prove that a particular speed law was violated, the defendant was the driver, and the offense occurred on a public thoroughfare.
    • The officer must also prove that the correct vehicle was stopped, and that the vehicle in question appeared to be traveling at the speed indicated on the RADAR equipment.
    • Special requirements for moving radar include:
      • Operator having sufficient training and experience
      • The radar instrument must have been in proper working condition (internal test)
      • The device was used where road conditions would distort the readings as little as possible (e.g., not raining)
      • The patrol car's speed was verified (speedometer)
      • The instrument's accuracy was tested (tuning forks)

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    Description

    This course provides an overview of traffic crash investigation, including interviewing drivers and witnesses, evidence collection, and scene protection. Trainees will participate in simulated traffic crash investigations.

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