Traffic Crash Scene Response

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TRAFFIC CRASH SCENE RESPONSE

A GUIDE FOR THE FIELD OFFICER

Clifford A. Prosser

Institute of Police Technology and Management


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Clifford A. Prosser

Traffic Crash Scene ResponseA Guide for the Field O fficer

~UNFUNIVERSITYof

NORTH fLORIDA.

Publisher:Institute of Police Technologyand ManagementUniversity of North Florida12000 Alumni DriveJacksonville, Florida 32224-2678(904) 620-4786 Fax (904) 620-2453www.iptm.org
http://www.iptm.org/http://www.iptm.org/


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DISCLAIMERThe information contained in this manual is based to the best of IPTM's knowledge onthe current practices in traffic crash investigation. However, neither IPTM nor the authorassumes any liability in connection with the use of this material. Every acceptableprocedure may not have been presented and some circumstances may require additionalor substitute procedures. Policies within organizations sometimes differ widely andwhenever this are in conflict with the information contained herein, the former shouldgovern.

COPYRIGHTCopyright 2007 by Clifford A. Prosser. All rights reserved. No part of this publicationmay be reproduced or transmitted in any form or by any means, electronic or mechanical,to include photocopying and recording, or by any information storage and retrievalsystem, without prior permission in writing from IPTM or the author.ISBN 1-884566-68-5

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11 1

Table of Contents1. Quick-tips scene task checklist ... 12. Preparation 2

The Notebook 2The Wreck Kit 2

3. The Radio Call 44. En Route ... 55. Arriving on the Scene ... 6

Positioning Your Vehicle 66. Scene Management and Control 87. Handling the Witnesses 118. Handling the Drivers 149. Handling the Vehicles 1510. Handling the Scene 17

Documenting the Scene ... 17Measuring the scene ... 23Documenting and Measuring Tire Marks ... 26

Skid Marks ... 26Offset Skid Marks ... 28Yaw Marks ... 28

Photographing the scene ... 32Securing and Retaining Evidence 33

11. Special Crash Situations ... 34Pedestrian crashes 34Heavy truck crashes 35Motorcycle crashes 37Rail crossing crashes 38Airborne vehicle crashes ... 41


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DedicationTo my Lord Jesus Christ, and to my wife and children.

Statement of PurposeI have written this text to provide the novice traffic crash investigator, andalso the veteran investigator who may sometimes be dispatched to anunfamiliar traffic crash situation, with a well defined but simple plan forsystematically handling the tasks that traffic crash scenes require.This is not intended to be a full blown accident investigation text. You willfind no formulae or calculations and no tutorials on specific analytical tasks.It is simply a step by step, easily understood system for responding to thescene safely and collecting the necessary information for a more in-depthinvestigation or reconstruction should it be needed later.If you have thoroughly and systematically managed your crash scene andcollected all pertinent information, you should be able to hand your case fileto a more highly trained investigator or reconstructionist and feel confidentthat he or she has been given the data needed to effectively describe theevents and, where appropriate, quantify the factors that make up theparticular crash sequence.My hope is that this text will encourage you to continue your training incrash investigation and possibly broaden its scope to include traffic crashreconstruction. While there are thousands of traffic crashes every day, manyof them serious, there are comparatively few police crash investigators whoview this discipline as a primary professional responsibility. You may wishto become one who does.

Clifford A. Prosser

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1. QUICK-TIPS SCENE TASK CHECKLIST1. Position your vehicle to protect the scene elements.2. Determine scene control measures needed.3. Make certain that the scene is secured and safe.4. Check for injuries.5. Check for and identify witnesses. Interview them.6. Obtain driver identification, licenses and insurance information.7. Obtain vehicle information.8. Call in for NCIC checks on drivers and vehicles.9. Perform scene walk through and observe evidence.10. Prepare scene diagram in notebook.11. Photograph scene and evidence before marking with paint or movingvehicles.12. Mark scene evidence appropriately with paint.13. Make additional photographs with evidence marked.14. Examine and photograph vehicle wheels and tires before moving them.15. Clear vehicles if possible.16. Determine best measurement method. Identify measurement reference

point(s) and reference line.17. Make measurements of scene dimensions and evidence placement. Record

measurements carefully and legibly on notebook diagram or measurementlegend.

18. Double check notebook and scene to make sure all measurements havebeen made and recorded.

19. Physically collect and document any evidence to be stored for furtheranalysis.

20. Further examine vehicles if needed. Hold vehicles in protective status ifnecessary.

21. Open roadway to traffic after all evidence has been documented.22. Properly store any evidence collected; maintain chain of custody.


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2. PREPARATIONThe NotebookIf you haven't already done so, develop a notebook system that you can use easily andreference readily at a later time. There should be some uniformity in the way you recordyour information for each case, so that you will not be unlikely to miss anything whileyou are at the scene or when you complete a report. You should plan on securing eachnotebook and retaining it for at least 5 years.The "Wreck Kit"As you begin to investigate serious traffic crashes, it will become very apparent to youvery quickly that you will need a rather diverse set of "tools" in order to effectivelydocument crash scenes, vehicles and items of evidence that can vary widely in type andcharacteristics. The most basic tools are, of course, simple measuring devices andcameras. But your kit can be as diverse and complete as you deem necessary. Below youwill find a fairly comprehensive list of articles that many experienced crash investigatorsinclude in their "wreck kits".

A good quality reflective safety vest Safety cones and flares A rolling type measuring device, large wheel preferred At least one 300' measuring tape At least two 100' measuring tapes At least two "pocket" type measuring tapes (25' or 35') A couple of 36" "yard sticks" for photo reference placement Scene marking paint Grade gauge, or 4' carpenter level Concrete nails for identifying reference point (and hammer) Good quality still camera (Digital and/or 35mm) Tripod Video camera, if desired Heavy work gloves Latex medical gloves Tire gauges ( both tread depth and inflation) Screwdrivers (both flat and Phillips) Wire cutters and needle nose pliers

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Magnifying glass Safety glasses Roll of twine, marked to 100' in l'increments with tape or marker Line level Zip lock plastic bags and paper sacks, labels and tags for evidence collection Lumber crayons for temporary scene markings Permanent sharp tip marker for marking evidence Stop watch, for traffic signal and traffic flow average speed timing Drag sled, for friction testing on roadway

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3. THE RADIO CALLBegin documenting information NOW! Obviously, there may not be a great deal ofinformation to be gleaned from the initial call, but there may be more than first meets the"ear". If you keep a call record in your notebook, note the time of the call. This willassist you in determining the most accurate time of incident possible for your report.Make a brief note about the weather and light conditions where you are when youreceive the call (note the time). This may be important in completing the report,particularly if you must travel an appreciable distance to the scene and significant timepasses before your arrival. Weather can change rapidly, and the conditions at the scenewhen the crash occurred are what need to be documented and reported, not just theconditions you observe when you arrive on scene. In other words, if it's raining when youarrive, don't simply assume that it was raining when the crash occurred. Conversely, ifit's relatively dry when you arrive, don't assume that those conditions existed at the timeof the crash. Roadway surfaces can dry quickly, particularly during summer after briefshowers. Early morning ice patches may melt very quickly, often within minutes, underthe heat of a rising sun. Do your best to document the conditions that existed at the timeof the crash.If the dispatcher indicates that the crash involves a commercial vehicle, try to determinewhether the vehicle is carrying hazardous materials. The dispatcher may not have anyinformation about this, but it never hurts to ask. If the vehicle is a tanker type vehicle,consider the possibility that it may contain flammable, corrosive or carcinogenic material.Having this information ahead of time will assist in planning your close approach, and inrequesting special assistance and scene control measures earlyon. Ifyou are unable toobtain any information with regard to types of vehicles and materials, plan on trying toobserve and identify the involved units as quickly as possible after arriving on scene.If the initial radio call doesn't provide any injury information, inquire of the dispatcherwhether any injury is reported by the caller. This information will help you gauge yourresponse in terms of speed, emergency equipment use, additional units required, and timesensitivity.

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4. EN ROUTEThis goes without saying, but I'll say it anyway. You can't do anything to help anyone ifyou don't arrive safely! While there may be a situation in which a few seconds maymake a difference in aid to victims, it is a relatively uncommon occurrence. It wouldsurprise most officers how little they reduce their response times with dangerous speedsand risky maneuvers. Consider this. Unlike during the years that I was patrolling thestreets and freeways of Birmingham, police liability is a tremendous, and ever increasing,concern. Individual officer liability is often not protected under the department umbrella.But that's not the most important issue. As a police officer, you presumably are behindthe wheel a great deal of your waking time. You have a tremendous exposure to accidentpotential and the law of averages isn't with you!Keep an ear on the radio for additional information that may be important to you inevaluating your approach. Additional accidents blocking roadways, or even thedirectional aspects of road blockages related to the crash you are dispatched on need tobe considered.If you are the primary responding unit, and you hear that one or more other units has beendispatched or has arrived on scene, have a plan in mind for task assignments. Ask yourassisting unites) over the radio to seal your scene, and personnel and time permitting, toidentify and detain any witnesses located. You may also want to obtain information fromthem about the best route into the scene for you.On close approach, be very observant of any unreported hazardous elements ormaterials. If a commercial vehicle is involved, look for any warning placards on thevehicle that may indicate dangerous substances. This is obviously more critical if thevehicle is overturned or any containers are ruptured or leaking.Upon arrival, make a note of the time, lighting and weather conditions, just as you didon dispatch. This may aid you later in reconciling any condition changes, or to answerduring further investigation or testimony any questions that may arise about the timelapse during response.

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5. ARRIVING ON THE SCENETreat your arrival on-scene much as you would a traffic stop. Don't assume that thesubject traffic crash is all that may be involved in the bigger picture. We all knowthat fleeing offenders frequently have traffic crashes after leaving a crime scene. We alsoknow that people harbor illegal substances and weapons in their vehicles. The peoplethemselves may be fugitives or may have outstanding warrants.Be courteous, but be careful and observant. Don't make assumptions that expose you,or others, to danger. Not all people are good people, and bad people have wrecks, too.Look for any conditions that could lead to the situation becoming worse. Trafficmoving at unsafe speeds near crashed vehicles, leaking fuel, terrain, or sceneconfiguration elements that obscure driver approach vision or might delay driverrecognition of the situation, and so forth.Defuse any potentially dangerous situations first. If you have fuel leaking and fireequipment is not on scene, make sure that they are dispatched. If no fire ensues, the fireequipment will still be needed to wash down any fuel deposited on the roadway. If aheavy diesel vehicle is involved and diesel fuel is leaking onto the roadway, advise anymotorcycle officers in the area of the hazard. Diesel fuel is extremely slick and hazardousfor motorcyclists, particularly in cooler weather.

Positioning Your VehicleYour vehicle is not your baby. It's a tool, and it's expendable. Granted, yourdepartment's purchasing agent may not see it that way, but you have to. As you arrive onscene, consider your vehicle to be a 5,000 pound protective barrier, complete withflashers and other highly conspicuous warning features.Determine where you can place your vehicle to provide the maximum scene protection.Of first priority, of course, are the crash victims and first responders. Secondarily, theconcerns are the involved vehicles and other evidence.If fire equipment or other police vehicles are already on scene, determine if they areplaced for maximum effect. If not, coordinate their relocation for the most effective sceneprotection.Be careful to position your vehicle in such a way that approaching drivers are not blinded

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by your headlamps. Also, take care not to place your vehicle so as to funnel traffic into anexposed or sensitive area of the scene. Be aware of the visual information that you andother responders are pro-viding to approaching drivers. Drivers navigating around yourcrash scene have to make decisions, and decisions are based upon information. Theinformation they receive from you should be as clear as you can make it.Check for injuries, even if you weren't dispatched on an "injury" wreck. Don't assumethat a radio call that indicates a "non-injury" wreck is accurate.(Author's note: One of the most tragic crashes that I have consulted on over the years wasan otherwise unremarkable T-bone collision in which a large sedan pulled from adriveway in front of a compact car. The speed of the "bullet" car was relatively low,perhaps mid to upper 20mph range. This is certainly not a speed that you would expect tocause serious injuries to a belted occupant. A nine year old girl was the front seatpassenger and was belted. She was walking around the accident scene, and a short timelater began to complain of some abdominal pain. She died a short time later from internalbleeding that was caused by a poorly fitted seat belt. Her liver had reportedly beenlacerated by the tensioned seat belt during the collision.It's a good policy to call medical units to the scene of a substantial crash that involveschildren. Seat belts often don't fit the pelvic girdle of children well, and they aresomewhat vulnerable to seat belt injuries during those transition years between specialcar seats and adolescence.)


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6. SCENE MANAGEMENT AND CONTROLTraffic crash scenes can be crowded and hectic. First responders, bystanders, mediacrews, other police officers, uninjured involved parties, "walking wounded" victims, andeven pets roaming loose may possibly compromise the integrity of evidence patterns andsources of potential information. Before you can effectively begin to document, collectand examine available evidence and information, you must first secure and preserve theintegrity of your scene as best you can. That's right, I said your scene. You areresponsible, so you need to take control and manage your scene well.You have already taken the first steps by carefully placing your vehicle, and those ofother responders, so as to protect the scene elements. But this is just the beginning ofthe scene management process. Collecting information for your report can wait a fewmoments. If your scene deteriorates and witnesses disappear, your information sourceswill be reduced and your investigation may be compromised.Police officers who have handled a great many serious crash scenes are all too aware ofthe "evidence eradication teams". This is a tongue-in-cheek way of referring to thewell-meaning servants of the people who are there to help. Fire medics and firefighters,tow truck operators, and media crews are all card carrying members of the team. Theymean well, but they can quickly compromise an accident scene if they don't know anybetter. The key here is education, beforehand when possible, and tactfulcommunication on scene. When the same fire crews and wrecker drivers respond to yourscenes over and over, try to spend a little time with them during down time to discusshow they can help you preserve the integrity of your scenes. Obviously, fire medics andambulance crews have got to be able to render all necessary aid and extract victimswithout interference. This may involve prying doors open or cutting roof posts. Also, theyneed to be able to render vehicles safe in whatever ways are necessary. This usuallyinvolves cutting battery cables. But there are aspects of the scene that are not safetysensitive, and you may be able to obtain some understanding about them from these"teams" so that they can help you preserve your scene.When you have one or more obviously deceased victims, or a victim has beenpronounced dead on the scene and has not yet been removed, treat their bodies withrespect. Cover the remains whenever possible, and try not to expose them to "gawkers"and "rubber-neckers". Treat them as you would want your family members treated.As quickly as possible you should locate, identify and (when possible) interview anywitnesses. Witnesses have a way of evaporating quicker than the radiator fluid from one

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of your crashed cars. Of critical importance is to identify and obtain reliable contactinformation. Crash scene environments often are not conducive to effective witnessinterviews. On the other hand, if a witness can be interviewed on scene, it may allow himor her to provide a fresher account and to literally point things out when necessary. Thiswill be dealt with specifically in the next chapter.When wreckers arrive, ask them to park out of the way until you are ready to movevehicles. They can obliterate, disguise or alter evidence, or even create false evidence, onthe road surface or the vehicles if allowed to enter the scene before you have documentedpost accident conditions well. DO NOT remove vehicles, or alter the positions orconditions of vehicles, until you have properly documented those positions and con-ditions. Once they have been moved, the situation cannot be replicated.You will very likely experience, if you haven't already, the pressure from yoursupervisors, and even subjective outside parties, to quickly re-open roadways or to "getback into service" and return to available call status. It's easy for me to say that you haveto dedicate the necessary time to your crash scene documentation and the eventual reportquality without compromise. But it's a fact of life that you will need to find a way tobalance efficiency with department operating procedures, limitations and needs. Thisconflict underscores the need for you to develop a concise and effective crash scenemanagement protocol.Sooner or later, you will be placed in a position to have to deal with media people. Havea protocol in place. First of all, become familiar with your agency's rules for mediainteraction. If your department has a public information officer or media liaison, refermedia people to that individual or section. Ifyour agency does not have a media policy inplace, you will need to develop your own. Of first concern is the integrity of your scene.This includes the care and protection of your crash victims, as well as the un-compromised status of your scene evidence. You may need to caution them aboutdragging their video cables and so forth through your scene evidence. Frequently, it's agood idea to tell media crews or reporters that you'll be glad to talk with them after youhave secured and documented your scene and made all appropriate notifications. Askthem to wait off to the side, and ask them politely when necessary not to disturb orinterfere with workers on the scene. They may not like to be put off, but they'll just haveto live with it. Remember ... You're in control! Be firm and decisive, but courteous.Your professionalism is on display.Make sure that any other officers that are on scene are engaged in necessary work. It ispossible that officers who are strolling around a crash scene can do more harm than good.If they aren't well trained in traffic crash investigation, or even if they are, they may alter


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the scene in some way. It's not unusual for officers to pick something up, look at it, andtoss it aside. I have seen officers who were supposed to be assisting the primaryresponder literally kick debris items off of the roadway before a scene was measured orphotographed. The integrity of scene evidence is critical, particularly at major crashscenes. Patterns of evidence are important, and shouldn't be disturbed.

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7. HANDLING THE WITNESSESIn handling witnesses to a crash, there are four needs predominate. These are to:1. Locate2. Identify3. Interview4. Track

The first three of those are critical to the scene management and early investigation. Thefourth becomes a factor when an investigation is completed and the case moves intocriminal or civil litigation.First, you need to understand the working definition of "witness". A witness is anyonewho can provide any information about any of the factors and events of a crashsequence that he or she perceives with any of the senses. Yes, this includes the non-driver occupants of the involved vehicles. I know ... you've always heard, and maybeeven been taught, that witnesses have to be totally objective non-involved people. Nottrue! A person who has first hand information is a witness, whether or not someonechooses to call him or her a witness. It staggers the mind how many people with veryimportant information and first hand accounts have gone un-interviewed after trafficcrashes over the years because they were assumed to be subjective and thus "tainted".Where a difference between involved and non-involved witnesses does exist is in theweight that you may give the witness accounts. The words of someone who has a vestedinterest in the outcome of an investigation may not carry the same weight as those of anon-interested (objective) observer.The handling of witnesses can be effectively pursued using two distinct phases of so- .called "W" questions.The first phase consists of thoroughly identifying the witness and establishingfoundational elements (including personal information) about him or her:What is your full name?What is your age?Where do you live?What is your telephone number?What is your cell phone number?Where were you when the crash occurred?


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Why were you there?What were you doing?Where do you work or attend school?Where do you plan to be in six months? In a year?The second phase is specifically related to the subject crash:What did you see?What did you hear?Who did what?When did certain events take place?Where did certain events take place?What was it that first drew your attention to the situation?Other clarifying and amplifying questions may need to be asked, but the "W's" give youan easy outline to work with.Although time and pressing scene management demands, as well as the needs of thewitnesses themselves, may affect your ability to interview the witness on the scene, it isvital that you interview them as early on as possible. Moreover, it is highly advisable tointerview witnesses on the scene, so that they can relate their accounts to sceneattributes and accurately refer to vehicles. It has been said by some crusty old crashinvestigators that witnesses often don't really know what they saw, and drivers don'treally know what they experienced. While this is much too broad a statement to promoteas a blanket truth, there is some truth to it. Some human-factors experts explain it thisway. As we see events unfold or experience them, we tend to record those in our memoryas mental snapshots. Later, when we are asked to recall those events, we tend to try torecall the sequence of events as mental video. But we have not recorded the events asvideo but as snapshots, with gaps between them, and we have subconsciously filled in thegaps with assumptions that may be erroneous. The lapsed time between the actualoccurrence of the events and our recollection of them at the time of the interview canmake the errors in our assumptions even more pronounced. Therefore, witnesses anddrivers should be interviewed as quickly as possible.In addition to the question of accuracy of memory, the integrity of interested parties in thedays following a crash may also be at issue. Witness and driver accounts may be taintedby the subjective "coaching" of attorneys, family members and insurance investigators.As stated above, witnesses and drivers should be interviewed as soon after the crashas possible.

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Witnesses and drivers should be interviewed individually, rather than together. This isthe only way to legitimately identify conflicts of information or inconsistencies. Separatethe parties and then interview them.

In the event that in-depth follow up interviews or interrogations are called for, it's a goodidea to video these when possible. When interviewing drivers in cases in which criminalcharges are a possibility, make sure that you obtain a Miranda rights waiver prior tospecific questioning about elements that could go to fault or guilt.When interviewing a juvenile, always have a parent or guardian present and have theparent or guardian sign a release form. This may entail delaying an interview until aparent or guardian can be located.The proverbial "eye witness" is a rare commodity. If you dismiss every person who hasknowledge of one or more of the factors and events of a crash situation because he or shedidn't "see" the collision, or the color of the traffic signal, or the vehicle approaching, orother specific points, you will be left with very few witnesses and very little information.If criminal charges are potentially pending, witnesses need to be contacted periodically toupdate their contact information and ensure their availability at trial.


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8. HANDLING THE DRIVERSAfter you have determined that a driver is "safe" in all respects, try to make earlyobservations of any evidence of drug or alcohol impairment. If there is evidence ofimpairment, it's a good idea to go ahead and secure that driver in the back seat of yourcar in most cases. This prevents him or her from consuming or purging anything whileyou are busy with other duties, and also prevents any possible injury to the individualfrom walking into traffic, etc. Obviously, you will want to pat the individual down, andevaluate the need for any restraints. If there is any evidence of some impairment, andthe source of the impairment is not obvious, have medical personnel check thedriver out as a precautionary measure. This is suggested even when the crash wasrelatively minor, as medical conditions may be at issue.Immediately after you have obtained driver's licenses, proof of insurance and/or otheridentification from the involved drivers, it's wise to call in for NCIC checks on them.Once again, this is a part of the management and control protocol to render the scenesafe. A great many fugitive and warrant arrests are made each year from routine checksmade during "routine" crash investigations and traffic stops.If the drivers are judged to be unimpaired and docile, it's a good idea to have each driverwait in a separate area until you can interview each one individually. If their respectivevehicles are in secured areas, it may be advisable to have them wait there. Begin theinterview by asking those questions designed to elicit the most basic information neededto simply fill in the report blanks. This gives you an opportunity to evaluate each driver'scondition and demeanor before the questions become more pointed and incident related.Recall the "W" system for witness interviews discussed in the last chapter. That will alsowork well for drivers. If you ask questions that allow the driver to speak freely and to"editorialize" his or her account of the crash sequence, make mental or actual notes aboutfollow up questions needed to nail down specifics or clear up possible inconsistencies.Make note of any part of a statement that conflicts with clear physical evidence thatyou've noticed.CAUTION: One of the most difficult situations for a crash investigator is where onedriver is injured and is not available or able to give an account, while the adverse driver isalive and well and able to be interviewed. DO NOT assume that the informationprovided by the "only man left standing" is true and correct. Make every effort tointerview the injured driver, if possible, before forming final opinions. Weigh everythingthat you hear against other available evidence.

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9. HANDLING THE VEHICLESBefore you do anything else, note the license plate and vehicle identification numbersof all involved vehicles and check them for stolen or wanted. This, again, is a part ofrendering your crash scene and situation safe. As stated earlier, many traffic crashes occurafter other criminal acts.It's a good idea in crashes that cause injury to mark the places of rest of each wheel ofevery vehicle with paint marks. The mark is made on the pavement or other surface onwhich the vehicle itself came to rest. Safety or blaze orange is a color commonly selectedfor its conspicuity and visibility. Also, indicate with paint which end of the vehicle is thefront, and either the unit number or the make. The most effective way, and generally themost accepted way, of marking wheel locations is to make a painted T-shape mark asclose to the wheel as possible, with the top of the "T" being the closest part of the mark tothe wheel (See The Scene After Marking on page 20). The top of the "T" should beparallel (along the ground) to the plane of the wheel, and the "stem" of the "T"should be at a right angle to that plane and in line with the hub center.This will document positions for any subsequent investigation once the vehicles havebeen moved. Follow-up work could potentially be done from paint-marked sceneevidence for months after the crash date, depending on weather and traffic exposure.Photograph the vehicles IN PLACE before moving them. This will insure that theconditions of the wheels and tires are documented. These are the parts of the vehicles thatare the most likely to be altered by movement. So make your first close examination oftires and wheels before the vehicles are moved. Remember, once vehicles are moved,the original positions and conditions of wheels and tires can never be replicated.In cases involving serious injury or death in which there is the potential for criminalcharges, place a hold on the vehicles as evidence until you are certain that their use asevidence has been exhausted. They are not just junk that the insurance companies arenow in control of. They are weapons, they are evidence, and they belong to you aslong as you need them.Make note of all control settings before anyone handles the vehicles. If you suspect orrecognize that rescue personnel have altered the vehicles in any way, find out exactlywhat they did and note that. Before the vehicles are moved, note the light switch, wiperblade and wiper switch positions, gear selection, speedometer and tachometer needleplacements, radio volume, seat belt positions and conditions, etc.

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If there are injured or deceased occupants still in the vehicles while you are on scene,make notes about their seating positions or rest locations.Observe and note damage patterns. Make careful note of contact damage areas andinduced damage areas (areas of damage with no direct contact), as well as forcedirection and other dynamic factors that could possibly correlate with damage.

CRASH DATADOWNLOADS FROM AIR BAG CONTROL MODULESIf you have the capability to conduct crash data downloads with the Vetronix system, orhave a colleague who does, this should be done while a vehicle is in its rest position, ifpossible. If it is necessary to move the vehicle for public safety and trafficmanagement reasons, make sure that the vehicle's systems are not "powered up"when the vehicle is moved. If they are powered up, this could alter the condition of anynon-deployment crash data records that may exist in the vehicle's airbag control module(ACM).A vehicle's crash data record cannot be affected unless the ACM is powered up. Adeployment record is locked and cannot be affected anyway, but non-deploymentrecords can potentially be overwritten by substantial jarring and jerking. Any downloadthat is conducted should be done, if possible, by the Data Link Connector (DLC) underthe dash. If it is not possible, the next preferred method is to connect directly to the ACMwhile it is still firmly in place in the vehicle. If connecting directly is also not possible,remove the ACM and preserve it as evidence for a bench-top download. Remember, if theACM is removed DO NOT POWER THE VEHICLE UP TO DO SO. Again,when themodule is not powered up, the data is not at risk.

(Information about the equipment and training availability for removing anddown-loading the Airbag Control Module is provided at the back of this text.)

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10. HANDLING THE SCENEThis chapter will deal with the observation, notation, marking and measuring of crashscene evidence. The "first responder" activities with regard to rendering the scene safe,taking care of the injured, dealing with drivers and witnesses, and other preliminarycontrol and management tasks were covered in earlier chapterS. For purposes of thischapter, we will assume that the scene has now been secured, leaving documentation ofscene evidence as the next task to perform.First, walk around the entire scene and view it carefully. Make a mental note of anydebris patterns, fluid spray or drainage patterns, tire marks, gouges and scrapes,blood or tissue stains or deposits, victim locations, and so forth. Attempt to identifyany scene attributes that may have factored into the crash situation.

Documenting the SceneTake a set of photographs before any paint is applied, if possible. It's always good tophotograph a "clean" crash scene, before any alterations have been made.Mark the accident scene carefully with paint. Identify the wheel placement of thevehicles, the beginning and terminal ends of any tire marks, any change in tire markdirection, any debris items or patterns, any fluid spray areas or patterns, any bodylocations, and any scrapes or gouges. In addition to allowing for additional scene work tobe done days or weeks after a crash, a well marked accident scene often makes evidencepatterns more apparent in photographs. Be thorough, but don't put so much paint downthat evidence is actually obscured.After a walk-through has been done, prepare a rough scene diagram in the notebook.Be careful to identify the bearing of the sketch; normally a "North" indicator will takecare of this. It's not a bad idea to indicate whether your "north" is compass north orrouted north. Locate all items of evidence, including the vehicles' final rest positions onthe diagram, making sure that the diagram is sufficiently large to allow for measurementvalues to be inserted legibly.Identify any tire marks observed as skid marks, scuff marks, yaw marks, or rollingtrack marks. Each type of mark requires a particular measurement protocol (method),and possibly a particular speed calculation protocol later in the investigation.


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Skid marks: Tire marks produced by hard braking, locking the wheels. Scuff marks: Tire marks made by a vehicle that is under some lateral force stress.This stress could be a function of a collision, or steering and/or braking input either

before or after a crash event. Wheels are usually rotating to some degree, and thedynamic mayor may not involve braking. Yaw marks: Curved tire marks created by a side-slipping vehicle. These are created

when a vehicle's speed is in excess of that which will allow a driver to steer in the arcthat he has asked the vehicle to negotiate. The wheels are rotating and they areexperiencing side force.

Rolling tracks: These usually occur when a vehicle has tracked through a fluid orsubstance that marks the vehicle's path. This could be radiator fluid, motor oil, blood,mud, or any number of things. The wheels of the vehicle are usually rolling in thenormal way. These marks may be continuous or broken "stamping" type marks, thelatter being from a tire that has picked up material on only a portion of its tread.

We will go into the measurement protocol for each type of dynamic tire mark (oneresulting from application of a force) in the next section. Rolling track marks need nospecial handling. The track, distance and terminal point, as well as the tracked substance,should be determined by observation.

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VVhoo! res t positions ---- .......

"'---- Scuffs

(~Googe

.- _"-~. ',\V\ lhoo ! rest pos it ions -------:1--- ........ ,' -. . . . . . . . . . . ~\

- . . . . .\, .. 'iilllili. ..

"--- Tire scuff

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SIC ENE RKING

Wleel rest positions ----i------...

Vllheel rest positions ----~

----------

"'---- lire scuff

ESCENEA R RKiNG20


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Wleel rest positions ---1---,. . . . .

."'---- Tire scuff

THE SCENE AFTER H iCLES RE D

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BASIC SCENE ING

THE SCENE A RTI RKS EDEvidence patterns and placerrentas welles vehicle rest positionscan still be identified weeks after the initial scene irwestcation,

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23

Measuring the SceneThere are two basic methods for measuring traffic crash scenes for making diagrams.

Grid Coordinate (90 degree) method Triangulation methodThe triangulation method is the most universally applicable. Virtually any point in anyaccident scene can be documented by triangulation. However, the grid coordinate methodusually is the easier and quicker to use if the scene configuration permits its use. Bothmethods are basic and simple to apply. Each method is explained below.Grid Coordinate: Every point in the accident scene is located with two measurementsthat are at 90 degrees to each other. The measurements are recorded relative to areference point and a reference line, or baseline. For example, a straight curb line of astreet makes a handy baseline, and a utility pole makes a nice reference point. Thereference point anchors the scene elements either east/west or north/south, and thebaseline provides the delineator for the second measurement to each point to be located.Every point will have two values, one theoretically east/west and the other theoreticallynorth/ south.Triangulation: For this method, two reference points are necessary, and the distancebetween them must be known or measurable. Every point in the scene to me measured isthen located relative to each reference point. In effect, the reference points provide two ofthe three points needed to construct a triangle. The third point could, for example, beprovided by a suitable point on an item of evidence. Two utility poles may be used as thereference points. The distance between them is measured and recorded in the notebook.The distance to a point on, say, an item to be located is then measured from eachreference point, and its distance from each reference point is recorded. Simply put, atriangle is created for the item of evidence so documented. The same procedure isfollowed in tum for any other items of evidence (or any other points) to be located. Thismethod is useful when there is no available straight line to serve as a base line.In documenting vehicle rest positions, it is necessary to document the locations of twopoints on the each vehicle. The wheels are customarily used because they are usuallyreasonably intact and available. By documenting the location of a point on each of twowheels on a vehicle, particularly the two wheels on one side, the vehicle's rest position(rest angle with respect to the roadway or to north) as well as its location can be recorded.


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REFERENCE L INEi0'S" 11'2"

11'2"./ "A ~ 3 _ 3 ' 1 _ 0 _ ' ~4_ .~~ . ~ ,p. ~.9'11"

GRID COORD INATE METHOD

24


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T R I A N G U L A T I O N

2 ~. .. . . J I I II I Ii II . . . " ", , . . .. J I I l II lI IL.

Measuring Roadway CurvesRoadway curves are measured by determining the radius of the curvature. This is doneby establishing a chord on one edge of the curve, either on the outside edge or the insideedge. Two points are selected some distance apart along the arc formed by the edge. Achord - a straight line - is then measured between the two points on the arc, and a middleordinate - also a straight line - is then measured at 90 degrees from the midpoint on thechord to the arc. The radius of the curve can be calculated from this information. Theexact methodology is described and illustrated in the following segment on measuringyaw marks.

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Documenting and Measuring Tire MarksSkid MarksAn officer can be so caught up in the length of skid marks as an indicator of vehiclespeed that he or she may neglect to document the exact location and characteristics of themarks. The location of skid onset is a critical piece of information for furtherinvestigation. It may be used to help determine whether that driver responded in anappropriate and timely manner to the situation, and the characteristics of the marks mayindicate whether or not there may have been a braking inequity or mechanical problem.Each end of each skid mark should be marked and documented, as should anyanomalies or changes of direction in the mark. Of particular interest is any suddendeflection, or angle change, of a skid mark, as this is usually a very clear indication of animpact at that location. It's common to mark each end of a skid mark with a painted "U"shaped mark, and to mark the skid path with dashed paint marks bordering the mark atintervals of the officer's choosing.Keep in mind that for purposes of calculating speed later in an investigation, the true netskid distance of a vehicle is needed, not simply the total skid mark distance. It should bepresumed that the rear wheels of a vehicle locked first in a braking skid, unless there isclear evidence that the front wheels locked first. Therefore, the following protocol shouldbe followed:

If a vehicle is stopped at the end of a set of skid marks, and the skid markpattern extends all the way to the vehicle's front wheels, the wheel base ofthe vehicle should be subtracted from the total skid mark pattern length toarrive at the skid distance to be used for any calculations.

If a vehicle is stopped at the end of a set of skids, and the skid mark patternextends only to the rear wheels, then the entire mark distance may be used.

If a vehicle is not at rest at the end of the marks, and it usually won't beunless it is a very minor collision or a pedestrian accident, then the markpattern should be measured and the wheel base subtracted. This is trueunless the skid distance of both front and rear wheels can be determined.

A driver should always be given the benefit of the doubt in the case of any calculation ormeasurement ambiguity.

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57~

M E A S U R IN G S K ID D IS T A N C E

Ev enthoug h the m a rk pa tte rn is 65 1 long ) true sk id d ista nce is only 5 7!.

Sk id d ista nce is 6 51! b ut. b ra king m a y b e lim i ted to re ar wheels,Y ou should a ssume tha t the roor w heels of a sk id d ing v ehicle lock ed first un le ss th e ma rk s a rec!e a rly front whee ! s kid s aUne beg innin g , If the veh icle is s topped a t the end of the skids) a nd thesk id m a rk s e xte nd to th e vehicle 's front whee l$ ~ the whee lb ase oUhs vehic!eshouid be subtractedfrom th e to ta l m a J 'k pattern to ob ta in the ne ts k id d is tance o f the veh icle . If the vehicle is s topped a tthe end o f tha m a rk s a rid the m a rk s stop a t th e re a r whee is t th e entire ma r k d ista nce ma y 0 0 used .Howe ve r, th e b ra k in g e fficie ncy ma y b e re duced a nd lim ite d to re ar w hee ~s,Ca re ful insp ectio n of them a rk pa ttern m a y a llow the officer to d a term ltisif front a nd rea r w hesls w ere b ra king .

Differentiating Front Wheel Skids from Rear Wheel SkidsIt's not always easy to determine where front wheels and rear wheels ended marking inrelation to the other. However, there are characteristic differences between front-wheelmarks and rear-wheel marks that help you make this determination. A front-wheel mark,due to weight shift and "nose dive", will normally have a darker outside border than arear- wheel mark will have. A rear-wheel mark, on the other hand, will normally show thetread pattern of the rear wheels more clearly.

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Offset Skid MarksOccasionally an officer will encounter a set of skid marks from a vehicle that are notreally overlapping, and perhaps not even straight. This can be caused by the terrain, byunbalanced or unequal braking force, or by some sudden steering input immediately priorto braking that offset the wheel track. When this non-overlapping effect is observed, thedocumentation and measurement protocol is as follows:

Locate and document each end of each mark. Measure each mark. Add the lengths of all marks together. Divide by the number of marks

The result is the average skid distance of the vehicle, and this is the distance to be usedfor any speed calculations.

M E A S U R IN G O F F S E T S K ID M A R K S

AD D AND AVERAG E TO D ETERM iNE VEHICLE SK ID D ISTANCE7 2 ' + 5 1 ! +821 + 7 3 ' =218 '278 ' + 4 = 69.Si

Yaw MarksFor a tire mark to be deemed a yaw mark, it MUST meet certain criteria:

It will be a curved tire mark in which longitudinal tread pattern is usually not28


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29

evident. Itwill be of decreasing radius, or an increasingly tighter spiral. Itwill show striations, or diagonal parallel friction lines, in the mark. Itwill exhibit "crossover", or out-tracking of the rear wheels.

If a tire mark doesn't meet these criteria, it should not be considered a yaw for purposesof speed calculation. However, it should be documented and marked as any other tiremark should. Beginning point, terminal point, and path should be documented andpreserved. The mark will be dealt with for analytical purposes as a scuff or a skid,depending on the situation.If a tire mark meets the criteria of a yaw mark, there is a very specific and sensitiveprotocol for measuring the mark for speed calculation purposes. The method is outlinedbelow:

At or just beyond the point where the rear wheels begin to track outside the frontwheels, a chord should be established and measured. A chord is a straight linebetween two points on the arc formed by the tire mark. A measuring tape can beused to represent the straight line.

The mid-point of the chord can then be located on the measuring tape and (unlessa second measuring tape is available) should be marked on the terrain or roadwaysurface over which the vehicle was moving. Then with the measuring tapepositioned at a 90-degree angle to the established chord, a middle ordinate ismeasured in a straight line to the outside edge of the tire mark left by the leadingwheel. The accuracy of this measurement is critical to the integrity of anycalculations to be made later.

The preceding steps will be repeated at a point further into the vehicle's yaw pathto ensure that the radius of the vehicle's path is decreasing.

The first of the following two diagrams shows the movements of a vehicle in a yaw andthe criteria required to identify a yaw. The second diagram shows the measurementmethod for a yaw.


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HICLEM ENTSIN,REQUIREMENTS F R CRITI D SICSPEED Y AW

r------ SHO ULD BED E CR EA SIN G R AD IU S

"CRO SSO VER", O R ~SEPAP. .AT ION PO INT

'------ STR IATIO NS IN TIRE M ARK

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C=CHORDM =MIDDLEORDINATER=RADIUS

____ --- SHO ULD BED E CR EA SIN G R AD IU S

"C RO SSO V ER ", O RS EP AA AT !O N PO IN T -----...._

F IRST ME .A .SUREMENTC=64'M=4.75'R= 11ft

C

SECOND ME AS UREMENTC=56'M= 5.981R=68'

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Photographing the SceneIt had already been stated that the scene should be photographed before it is marked, andafter it is marked. With that understood, we will look at a few more specifics with regardto photographing the scene, vehicles and items of evidence.Camera angles can be misleading. Items may appear to be closer or farther away to orfrom other objects or landmarks, or may be distorted in size because of cameraperspective. Given that fact the following should be considered a cardinal rule:Always photograph every piece of evidence and the vehicles, as well as theoverall scene, from a number of different angles.In that way, a true "picture" of the scene can be obtained form the collective images tosupport the measurements made and scene illustrations prepared.If it becomes necessary to use wide angle or tight angle (zoom or macro) settings to shootcertain items, always take some shots at a lens setting closest to that of the natural eye, ifpossible. That setting is somewhere around 49mm to SOmm, but opinions differ on that.You should be able to judge a pretty close setting.It is a good idea to use flash for supplemental shots, even during daylight, for contrastand clarity.As technology moves ahead very swiftly, digital photography is establishing itselfprominently in police evidence documentation and collection. A good quality digitalcamera allows an officer to leave an accident site knowing, not hoping, that he or she hascollected the necessary images.A good lightweight and versatile video camera is a good addition to the "wreck kit". Ifavideo camera is used, the same information should be documented as would be in stillphotography. The key in quality videography is to pan the camera s .. I .. 0 w .. I .. y.Image stability is also very important. Be slow and steady with camera movements.

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Securing and Retaining EvidenceThere will no doubt be times when you will want or need to physically collect items ofevidence for further examination, analysis, or to present during trial. The methods ofcollecting and retaining are varied, but those listed below are a few common applications.

Organic or fluid evidence should NEVER be placed in a sealed plastic bagor container. This type of evidence will mildew or mold quickly without air.Use paper sacks for this type of evidence. Swabs of blood, saliva, beveragesplatter, unknown liquids, body tissue, etc. should be collected in this way.

Small plastic zipper lock bags or film canisters will often hold small vehiclelamp bulbs very nicely. EVERYTHING collected should be carefully marked for identification and

chain of custody handling. Depending on the type of evidence, this mayinvolve "bagging and tagging", or even marking or etching the object itselfwith a permanent marker or other tool. When a film canister, zipper type bagor paper sack is used, the container should be sealed and initialed with eachopening of the container. Change of custody should be tracked either on thecontainer or on an accompanying form.

Vehicles should be locked down in serious crashes and retained for furtherexamination if necessary prior to being released. No one outside theinvestigation authority should be allowed access to the vehicle( s) untilprocessing has been completed. They belong to you until you are throughwith them!

Swabs of fluids may be done with Q-tip type implements or cotton or gauzeswabs. Swabs of different substances should NEVER be packagedtogether.

Large items, such as vehicle bumpers, tires or wheels, full lamp assemblies,etc. should be marked and packaged in an appropriate way to preventalteration. A size consistent ready made cardboard box, or a fabricatedcardboard container specially fashioned to size and shape, should suffice.

Scale evidence photo-reference cards with article identification numbersshould be employed when photographing items of evidence, and care shouldbe taken to reference them to a fixed location on the accident site or vehicle.


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11. SPECIAL CRASH SITUATIONSEvery officer will almost certainly be dispatched on traffic crash incidents that are not ofthe usual "car into car" or "car into tree" scenario. The possibilities are almost endless,but a few of the more common less-usual situations will be addressed here.Pedestrian CrashesThe key here includes scene control, protection from contamination and carefulexamination. Pedestrian crashes can be extremely severe in terms of injury, but mayproduce relatively little evidence that catches the eye. The most important considerationin handling a pedestrian crash scene is to perform a close examination for evidenceslowly and carefully. Bodily fluids on vehicle and roadway surfaces, clothing transfers onvehicle and roadway surfaces, and body tissue smears or transfers on vehicle androadway surfaces may be hard to identify at first blush. Small items of apparel or jewelrymay be thrown about and need to be located and mapped.If the incident occurs at night, auxiliary lighting sources may have to be employed.Persons walking about the scene need to be limited to those who absolutely need to bethere, and who understand the need for evidence integrity.Of great importance in pedestrian / vehicle incidents IS locating, documenting andcollecting information about the following:

Pedestrian's path into path of vehicle Pedestrian's location at time of impact Pedestrian's position at time of impact Vehicle's approach path to impact Any evidence of vehicle driver's evasive actions Pedestrian's clothing color and reflectivity Pedestrian's post impact ground or roadway strike point Pedestrian's post impact rest location Vehicle evidence that shows pedestrian's interaction with vehicle.

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Heavy Truck Crashes(Commercial Vehicles, including Buses)

There are three primary things that make heavy truck crashes different from traditionalpassenger vehicle crashes:

Their size makes any collision with passenger vehicles or other smaller vehiclesan extreme "mismatch".

Their mechanical complexity and articulated composition often result in a morecomplicated dynamic analysis of a crash.

The Code of Federal Regulations compliance issues in a heavy truck crash requirea thorough examination of the vehicle and paperwork in serious crashes.

In the case of a heavy truck that is braking efficiently, there should be a tire mark for eachtire on the rig. The only caveat here is that the front wheels (steer axle wheels) oftendon't fully lock, so that the front-axle marks won't always be as clear and evident as thedrive-axle and trailer-axle marks. Because their steer-axle wheels often don't fully lock,tractor trailers can usually be more effectively steered while braking than passengervehicles, but their resulting skid paths may be rather varied and require more time andeffort to document.Tractor trailer combination rigs have at least ten wheels and three axles. Most have fiveaxles and eighteen wheels. Each end of each axle is equipped with air-brake systemcomponents that must be within certain specifications to be roadworthy. From bumper tobumper, there are myriad compliance issues to be considered. Nevertheless, even when acertified inspector is not available, an officer who is not certified or even trained inheavy- truck examination for compliance, can effectively document the condition of aheavy vehicle for later consideration.Because the center of gravity of a heavy truck is much higher than that of a passenger car,there is almost always a severe "override" during a collision. The override creates a greatdeal of down-force, and usually produces gouging, scraping and scuffing by the carimmediately after impact.


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Heavy Truck Crash Task Checklist Call a certified DOT inspector to the scene, if one is available and the crash

severity warrants. Determine and document area of impact. Determine pre-impact skid distance, if any, and document. Determine post-impact skid or travel distance and document. Identify, mark, and measure each tire mark located for all vehicles. Record the DOT number from the truck tractor cab. Follow usual driver, witness and vehicle information methodology. Determine gross weight of the commercial vehicle Determine the axle weights of the vehicle, if possible. This may be available from

scale tickets if there are any with the truck. Locate and temporarily retain the driver's log book(s), particularly if there hasbeen a death and further investigation is forthcoming. Record the type of transmission, and number of gears. Determine what gear he was in on approach and at impact. Determine if the tractor had cruise control, and whether it was in use. Determine whether the tractor had "jake brakes", and whether they were being

used. Identify the setting. Identify any possible driver distractions in the truck cab. Observe and document damage patterns and force direction evidence as you

would with any vehicle. Examine tires and braking components for unusual wear or failure evidence.Photograph brake components and interior of wheels thoroughly. Determine the probable sight lines for each driver, and anything that may have

interfered with the drivers' perception of the other vehicle. In overturn accidents, determine whether a load shifted or broke free. Document

and photograph. Determine whether any load retention devices (straps, chains,etc.) failed. Document and photograph.

Place vehicle under a hold and retain it for further inspection if needed. Note: youare probably responsible for the spoliation of refrigerated goods. Make sure thatloads are cared for by towing entity.

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Motorcycle CrashesLike heavy trucks, motorcycles are articulated vehicles and crashes involving them mayrequire some special handling. Scenes should be carefully examined for path and impactarea evidence. Most of the documentation tasks are very similar to those for passengervehicle crashes, but there are a few obvious differences.There are two primary differences between passenger vehicle and motorcycle crashes:

The operator, and any passenger, are usually ej ected in some way from themotorcycle at some point in time during the accident sequence.

The motorcycle almost always overturns at some point in time during thesequence of events.

Motorcycle Crash Task Check List Usual driver, vehicle and witness documentation. Document vehicle places and positions of rest. Determine and document places of rest of any operators and passengers. Determine and document the gear that the motorcycle is in. Measure the damage wheelbase of the motorcycle. Identify and document area of impact. Identify and document any tire marks. If crash severity warrants, implement photography protocols. Pay particular attention to and document any unusual characteristics ofmotorcycle tire marks. Try to identify and document the ground strike points of any ejected motorcycle

occupants. Locate and document any motorcycle overturn locations. Locate and document

any resulting scrapes and gouges. Measure all tire marks and linear side-slide distances. If possible, measure seat height of the motorcycle (to possibly be used in

calculations of rider vault speed.) Follow all usual methodologies for documenting any evidence on, or produced byany involved larger vehicles.


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Rail Crossing CrashesThese are unique incidents, and require certain criteria to be met in order to be considered"traffic crashes". First, in most jurisdictions the incident must occur in a roadway-railroad track crossing, and must involve a non-train unit of some type before it ishandled as a traffic crash. If there is a mishap on the track anywhere other than at such acrossing, it will be regarded as an industrial accident and is investigated as such.As in the case of a heavy truck striking an automobile, any collision between a train and aroad vehicle is a "mismatch". Obviously, a train cannot approach an area of impact froman unpredictable path or angle, being pretty much destined to follow the track that it's on.However, the predictability of the train's path is no guarantee that the crossingenvironment will afford ready observation of an on-coming train to the driver of a truck,car, or motorcycle, or even to a bicyclist, who is approaching that crossing.A railroad engineer is not required to possess or produce a motorist's state driver'slicense. Although not a "driver" in the usual sense of the word, the engineer is the"driver" for incident reporting purposes and should be able to produce some kind ofpersonal identification and an authorization to operate the railroad engine.One of the most important documentation tasks for a crossing crash investigator is todetermine the "sight triangle" (see the following diagram) available to the approachingvehicle driver. Are there any limitations to the view? Is there a sufficient perception andresponse distance for a vehicle driver to stop short of impact with an approaching train?Rail Crossing Crash Task Checklist

Position your car carefully and strategically as with any scene, but take specialcare not to park on or very near tracks.

Be aware of multiple tracks. Non-involved tracks may still be in service. DO NOT crawl or climb under railroad cars or on car-coupling equipment.

Sudden train movements, even slight ones, can cause serious injury. Locate and interview the conductor, not the engineer (who is required to stay with

the engine) to obtain information about the train. Inquire of the conductor about any hazardous materials on board. Determine their

stability and status. Note the grade crossing DOT number. This should be found on a cross-buck post

or on other equipment at the crossing. Consult and document the inspection report which should be in the lead engine

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39

and will have information about the condition of the engine. Consider the locomotive number to be the VIN for reporting. Check with the conductor for a "consist" list, detailing the make-up of the train.

Bills of lading should also be available. Determine and document the post impact travel distance of the lead engine. If a rail car is stopped in the crossing, note its number and have the

conductor find it on the consist list. He can tell you how many carshave already gone through the crossing, and how far down track thelead engine is.

Determine if, when and where any emergency braking began, if possible. Thiscan sometimes be determined by locating where sand was blown onto the trackrails to improve friction.

Make sure that the on-board recording devices in the lead engine are secured andpreserved for download. Information about speed, braking and equipment use canoften be obtained from them.

Determine the track speed for the area. Determine if there are whistle boards posted, and record their locations. Identify the rest locations and positions of any other involved vehicles or persons. Process the scene; measure, document and photograph. Identify any crossing anomalies; rough areas, angles, steep grades, etc. Follow usual witness processing procedures. Determine if the lead locomotive's light was working. Determine whether the train's warning horn was heard on approach. Verify the presence of and identify the location of any and all warning devices:

Cross bucks Reflectorized devices Stop signs Rail crossing warning signs Rail crossing pavement markings Speed limit signs for roadway traffic

Determine and document the sight triangle if it is limited in any way.


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RAIL CROSSING APPROACH SIGHT TRIANGLE

';\"\\\\\"\?- r i@ \ ~'*:~. \

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Airborne Vehicle or Occupant CrashesIf a vehicle, vehicle component, or occupant, are airborne at any time during an accidentsequence, a very specific documentation protocol is needed.For purposes of speed calculation, an airborne situation permits the most accurateestimation possible. Everything that is airborne accelerates toward the center of the earthat the predictable rate of 32.2 feet per second per second, or 32.2 f t /sec/sec, as a functionof gravity. Therefore, as long as the following three data can be accurately determined,the speed at takeoff can be calculated:

The horizontal distance that the vehicle, person or object traveled while in the air. The vertical distance that the vehicle, person or object descended or ascended

while in the air. The angle of take-off, positive or negative, if takeoff was not from a level surface.

The usual scene, vehicle, involved persons and witness documentation tasks must, ofcourse, be performed. But, in addition, the above three data need to be determined anddocumented.The scene-processing task checklist is the same for a crash with an airborne componentas for any other crash except for the following two items:Bear in mind that the vehicle's change in vertical distance (height) as a result of beingairborne, is measured from the vehicle's center of mass (not from its tires or roofline) attakeoff to the vehicle's center of mass at its last point of touchdown (not necessarily itsfinal place of rest). A vehicle's center of mass is generally considered to be atapproximately one third the vehicle's standing height.The scene processing task checklist is the same for a crash with an airborne component asfor any other crash, except for the following two tasks:

Locate and document the location of the vehicle's last contact with the ground, orthe article's last contact with its "host".

Locate and document the location where the vehicle, person or article struck theground.


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H :::Ho rizon ta lV ::: Ve r tic a l

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MISCELLANEOUS INFORMATION

All CAD illustrations in this book were drafted by the author using Autosketch Version 9.Training in the use of the Autosketch program was provided by Institute of PoliceTechnology and Management instructor Mike Reade. The course is entitledComputerized Collision Diagramming, and information regarding the course, and othertraffic related courses, is available through the Institute of Police Technology andManagement and the institute's web site.

Vetronix Crash Data Retrieval (Airbag Control Module download) training is availablethrough the Institute of Police Technology and Management, as well as through theCollision Safety Institute. Information on both facilities is available on their respectiveinternet web sites.

ACKNOWLEDGEMENTSInformation for this book, as well as manuscript review and preparation assistance, wasprovided to the author by the individuals whose names appear below. My sinceregratitude is extended to them for their valuable time and efforts.Officer W. J. "Jim" Griffin, Fultondale, Alabama Police DepartmentCpl. David Steward, Alabama State TroopersMr. Hal Lockridge, Special Agent, Norfolk Southern CorporationMr. Al Ellis, Institute of Police Technology and Management


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INDEXA Air bag control module 16

Airborne crashes 41Articulation 35, 37Autosketch 43Average (skid distance) 28Axle weight 36

B Bearing (Compass) 17c

CAD 43Cameras 2,32Carpenter's level 2Center of mass 41, 42Chord 28,31Collision Safety Institute 43Compliance issues (DOT, commercial vehicles) 35, 36Computerized collision diagramming 43Conductor 38, 39Consist list 39Crash data downloads 16Cross bucks 38Crossover (out-tracking) 28,29, 30, 31Cruise control 36

DDamage patterns 16Data Link Connector 16Deceased (victims) 8Decreasing radius 28, 29, 30, 31Digital photography 32DLC 20DOT inspector 36DOT number 38DOT Crossing number 38Drag sled 3

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E Engineer 38Evidence, collecting and retaining 33

F Fluid stains 17Force direction 16Front wheel skids 27

G Gloves 2Gouges 43Grade gauge 2Gravity 41Grid coordinate 27Gross vehicle weight 36

H Hazardous materials 38Heavy truck crashes 35Hold (custody of vehicles) 15Horizontal (travel distance) 41, 42

I Inflation gauge 2Institute of Police Technology and Management 43J "Jake" brakes (Jacobs Engine Braking System) 36

Juveniles (witnesses) 13L Latex gloves 2

Lighting 8Line level 3Load retention devices 36Locomotive 39Locomotive number 39Log books 36Lumber crayons 3


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M Magnifying glasses 3Marking paint 2, 21, 23, 24, 25, 26Marking the scene 17,19,20,21,22Measuring tapes 2Measuring the scene 23Measuring skid marks 26Media 9Middle ordinate 29, 31Miranda rights 13Motorcycle crashes 37

N NCIC 14Notebook system 2

oOffset skid marks 28

pPatterns of evidence 10, 13Pedestrian crashes 34Photography 32Photo reference cards 32Positioning (vehicle) 6

QQuick tips, scene response guidelines 1

R Radio call 4Radius 28, 29Rail crossing crashes 38Rear wheel skids 27Recording devices 39Reflectorized devices 39Retaining evidence 33Rolling tracks 18

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SSafety cones 2Safety flares 2Safety glasses 3Safety vest 2Scrapes 43Scene diagram 17Scene management 8Scuffs 17Securing evidence 33Side slide (Motorcycle) 37Sight triangle 38, 40Skid marks 26, 27, 28Stop watch 3Striations 28, 30

T Time 4Tread depth gauge 2Triangulation 23, 25Tripod 2Twine (incremented for measurement) 3

U Unequal (braking) 27V

Vehicles; handling 15Vertical (travel distance) 41,42Video camera 2, 32YIN 15Vehicle Identification Number 15Vetronix 16

W Weather conditions 4Whistle boards 39Witnesses 11Work gloves 2


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Wreck kit 2Wreckers 9

yYard stick 2Yaw marks 28, 29, 30, 31

z Zip lock bags 3

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ABOUT THE AUTHORClifford A. Prosser, was honorably discharged in 1972 from the U. S. Army MilitaryPolice. From 1972 - 1986 he served with the Birmingham (Alabama) PoliceDepartment, where he was assigned to a wide variety of functions over the years,including traffic accident (crash) investigation. He has investigated more than 3000traffic crashes at the scene and has attended courses up through the level of traffic crashreconstruction at IPTM. As a legal traffic crash investigator/reconstructionist, he hasevaluated over 750 cases for individuals, private businesses, insurance companies andlaw firms. He has given expert testimony as a reconstructionist in courtroom anddeposition in over 200 cases. He is now owner of a traffic crash investigation andreconstruction company in Birmingham.


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Traffic Crash Scene Response

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Transcript of Traffic Crash Scene Response