FORENSIC SURVEYING FORENSIC SURVEYING Part 2

Transcription

1 FORENSIC SURVEYING FORENSIC SURVEYING Part 2 BERNARD M. TELATOVICH, P.E., ESQ. PART 2 BERNARD M. TELATOVICH, P.E., ESQ. CONSULTING SERVICES & INVESTIGATIONS, LLC New York January 2017 What is Evidence? Evidence any species of proof, or probative matter, legally presented at a trial of an issue, by the act of the parties and through the median of witnesses, records, documents, exhibits, concrete objects etc. for the purpose of inducing belief in the minds of the court or jury as to their contention. (TAYLOR V. HOWEARD, 111 R.I. 527, 304 a.2d 891,893) ( BLACKS LAW DICTIONARY) Types of Evidence? Primary - Original Evidence Secondary - Second Hand Prima facia - assumed correct unless Extrinsic - extraneous Parol - verbal/testimonial Direct - Circumstantial Expert Etc. What is Evidence- to the Surveyor? Evidence the state of being evident, plain, apparent, or notorious (WILSON) Evidence something used to prove, ascertain, or lend support to a fact, circumstance, or situation. Anything accepted in court that will aid in retracing and fixing a boundary. Reliable data, objects, or documents that can be applied by the surveyor to locate the record boundary. (HERMANSEN) What is a Fact? Fact a circumstance, event, or occurrence as it actually takes or took place, a physical object of appearance as it actually exists or existed. An actual and absolute reality. (WILSON) Fact a thing done, an action performed or an incident transpired; an event or circumstance, an actual happening which has taken place.(blacks LAW) Fact something you can prove. (Mr. TELATOVICH) 1

2 The Jury: Trier of Fact? Who assists the trier or fact to understand evidence that requires specialized knowledge or training? Court Hearing Officer Administrative Judge Who is the trier of the Law? Why the EXPERT of course!! Trier of the Law? The Judge: Forensic Experts Recognize pertinent evidence at the site Appropriate collection of evidence Photographs Preservation of Evidence Understanding Methodology Wood and Tree Evidence? Tree references in property descriptions may be treated as monumentation in the ground. Terminus of the line is typically at the center of the tree, unless the description indicates otherwise. Line of trees planted as boundary line is admissible in evidence. If the tree is lost or destroyed, it should be treated similar to any missing. (or stake?) Stake Evidence Stakes designated in a legal description typically designate an imaginary point e.g. stake along the side of the cartway designating the r/w. A placed stake fixes the corner similar to monumentation The issue relative to stakes is they are no of a permanent nature. 2

3 Scribe marks in trees and on other features Using Forensics Survey - Who would use the information? - How is the information used? Marking are typical evidence that is used to establish fact. Restated, it tells a story about the survey. - Can I be involved? - ACCIDENT RECONSTRUCTION what is it? INTRODUCTION TO ACCIDENT RECONSTRUCTION PRINCIPLES PRESENTED BY: BERNARD M. TELATOVICH, P.E., J.D. CONSULTING SERVICES & INVESTIGATIONS, LLC 758 REDFERN LANE, BETHLEHEM, PA ACCIDENT CAUSATION Driver Tactics Perceive Decide Perform Driver Strategies Human Factor an action which increases the probability of successful evasive tactics. The motor vehicle code regulations are designed to increase beneficial driving strategy. Abbreviations: Equations: 3

4 Conditional Factors Contributing to Traffic Accident Causes 1. Human Factors 2. Vehicle Factors 3. Environmental Factors This is the Black Box for a Flight recorder Basic Mathematical Concepts Acceleration Acceleration is the change in velocity over a period of time. a= dv/dt e i a= (v - v ) / t SEE HANDOUT MATERIALS Velocity Velocity, a vector, is the rate of change of distance with respect to time v= dd/dt or d/t v e² = v i ² + 2 a t SEE HANDOUT MATERIALS Distance Distance is a linear measurement from some point. d=velocity x time i d = v t + ½ a t² SEE HANDOUT MATERIALS Examples using equations Practical Application Vehicle Speed - A Vehicle traveling 40 miles per hour will travel how many feet per second (fps)? 1 MPH = 1.47 fps 40 miles x fps = 58.8 fps A vehicle traveling 40 MPH covers 58.8 feet every second A vehicle traveling at 100 fps will travel how many miles in one hour. 100 fps / 1.47 = 68 MPH In one hour this vehicle will drive 68 miles. The biggest mistake is made with this conversion. Time Distance analysis A driver is approaching a light which has a protected left signal that stays green for 8 seconds. He alleges he saw the arrow when he went through the previous green light 600 feet away. Do you believe this driver that alleges he still had the left green arrow as he went through the intersection? Solution If the speed limit is 35 MPH, this vehicle is traveling at 51.5 fps (35 x 1.47). It would take him approximately 11 2/3 sec. (600/51.5) to travel that distance. To travel the 600 feet in 8 seconds, the vehicle would be traveling at 75 fps (600 feet/8 seconds) or 51 MPH (75/1.47). Note this does not account for deceleration -- Sight Distance Problem Acceleration - Deceleration Intersection Accident A vehicle at an intersection (using PENNDOT and AASHTO standards) has available sight distance of 540 feet. The driver alleges he had only 100 feet available and saw the approaching vehicle only as it hit him. Do you believe the statement? For Discussion At a given speed a vehicle travels 540 feet in a given time. For example. At 30 MPH it takes t= 540/((30)(1.47)) = 12 sec. to travel 540 feet t=100/((30)(1.47)) = 2 ¼ sec. to travel 100 feet Acceleration F = ma a=f x g g=gravity 32.2 ft/sec/sec f=drag factor Normal f=0.15 High range f=0.30 Motorcycle f=? Deceleration Engine braking f= Max comfortable braking f=0.3 Coefficient of Friction Static v. Dynamic f= Other factors rain, ice etc. SEE HANDOUT MATERIALS 4

5 Acceleration Deceleration- Problem A vehicle accelerates from a stop to 20.4 mph in 6.5 seconds. How fast is this vehicle accelerating? e i (v - v ) / t (30-0)/6 = 4.6 ft/sec/sec Why 30? (hint - units) What is the drag factor for this accelerating vehicle? Restated How many g-s is this vehicle driver feeling? 1 g = 32.2 ft/sec/sec So a= (f ) (g) f= a/g = 4.6/32.2 f= 0.14 (compare with prior slide) Kinetic Energy V =MPH (miles/hour) FPS (ft/sec) KE = ½ m v ² = ½(W/g)(1.47 v)² (A) Work = F x d (B) =(fw) *d Work = KE (Kinetic Energy) 30 f d =V² therefore-- d= V²/30f V= (30fd) f=v²/30d Problem: You are told by the expert that the vehicle was skidding on asphalt a distance of 300 feet and he calculated the Speed of the vehicle at 80 MPH. Is this plausable? (hint solve for f (0.71) is that reasonable?) YES Skid Marks - Wikipedia A skid mark is the mark a tire makes when a vehicle wheel stops rolling and slides or spins on the surface of the road. In car accidents, skid marks are caused by rubber being deposited on the road, much like that of an eraser leaving pieces of rubber on a paper. Skid mark (per the Traffic Accident Investigation Manual) is usually bitumen softened by friction generated heat and Speed required to slow to a stop! SEE HANDOUT! Sample Calculation Using Nomograph SEE HANDOUT Vehicle Collisions Point of First Contact Point of Maximum Engagement Last Contact Point Full Impact some part of colliding surfaces reach the same speed during impact. Partial Impact aka swipe Thrust force between a vehicle and another object which results in collapse of vehicle parts (damage) 5

6 Skidding Vehicles Examples of Skid Marks Often the speed of a vehicle can be determined based upon skid marks. Skidmarks are tire friction marks made by a tire that is sliding without rotation on a surface. The mark may be made as a result of braking or post collision damage. SEE HANDOUT There are a variety of skidmarks! Yaw Marks Example of Yaw Marks A Yaw mark is a scuffmark made on a surface by a rotating tire which is slipping more or less parallel to its axis. Yaw marks are often referred to as centrifugal skidmarks, critical speed scuffmarks, or sideslip marks. The equation : V = 15 R (e + f) where R=radius e=superelevation (cross slope) and f = side friction Example Problem What is the maximum comfortable turning speed for a car turning at a radius of 50 feet. V = 15 R (e + f) e= cross slope or super-elevation assume 0 f= comfortable = 0.30 max is approximately 0.70 Are we talking sideslip? What is the maximum comfortable turning speed for a car turning at a radius of 50 feet. V = 15 MPH (See handout) Yaw Marks indicate side slip provide R (radius) Thus, solve for the speed assuming an f So V = 15 x 50 ( 0+0.3) = 15 MPH Use the 1 st one third of the yaw to determine the critical R 6

7 Linear Momentum Momentum is conserved in collisions Newton s Laws F = ma a= V/ t F= m V/ t F t = m V So Impulse = the change in Momentum Conservation of Linear Momentum F₁ t = m₁ V₁ F₂ t = m₂ V₂ F₁ = -F₂ Substitute the above into the top two and add together m₁ V + m₂ V₂ = 0 M₁+ M₂ = M₃ + M₄ W₁V₁ + W₂V₂ = W₃V₃ + W₄V₄ Momentum Key Points Momentum can only be used to determine the pre and post-impact Velocity The result is Delta V (for each vehicle injury factor) V 1 Vehicle Collisions V2 After Collision Point of V1 Contact x y V2 o x Angle of Departure is critical Velocity is a vector with magnitude and direction (Speed is the resultant - magnitude) Vehicle Collision-Momentum Before Collision V 1 y o V2 Point of Contact x After Collision y o V1 V2 x Momentum Points to Ponder 1. Momentum (P) = mass (in slugs) times velocity (V) - it s a vector quantity meaning it has magnitude and direction> 2. Momentum is always conserved In any group of objects that act upon each other, the total momentum before the action equals the total momentum after the action. 3. In this analysis the approach and departure angles are critical. How one determines this is very critical to the calculation. The best evidence if this is typically marks on the road and vehicle damage. 4. A reasonable representative range of approach and departure angles makes the calculation more reliable (a reliable range/sensitivity.) 5. Momentum analysis is less sensitive the closer the impact angle is to 90 degrees, the closer the vehicles are in weight, and when the vehicles move a reasonable distance after impact. 6. Momentum is very sensitive when the weight of the vehicles differ significantly, i.e. a large truck impacting a small vehicle. 7

8 Accident Reconstruction Sketch ACCIDENT RECONSTRUCTON SKETCH This is a typical 90 degree collision where the vehicles do not remain together. The angles of approach are not very sensitive (90 degrees 80 degrees), however the angles of departure are always critical in evaluating an accident. Weight shifts can create a parabolic departure. This is a typical 9o degree accident where the two vehicles remain together. You can imagine the result to the drive in an accident like this!!!!!! What do the vehicles look like? ENERGY Work is a measure of what effect the force has on changing the object Work is also defined at the product of the Force and the distance through which the force acts. The work equation: W= F times d = Fd F= force (lb, N) d= distance (feet,meters) W= work (ft-lb, N-m) Barrier Equivalent Velocity Equivalent Barrier Speed Equivalent Barrier Speed (Barrier Equivalent Velocity) Campbell vehicle damage and dynamic force deflection characteristics (stiffness) of the vehicle structure could be used to estimate the energy absorbed in permanent (plastic) defamation of a vehicle. The force deflection characteristics (crush) of the vehicle structure could be estimated from frontal The Energy is now equated to the Kinetic Energy a vehicle would have to possess in a barrier impact test. This velocity is called EQUIVALENT BARRIER SPEED - EBS We obtain the value in the following units (in-lbs) convert to (ftlbs) EBS = v = (2gE/w) The result is the EBS for each vehicle at 8

9 RELATIONSHIP BETWEEN WORK AND ENERGY Energy is transferred between different objects by doing work. The greater energy an object possesses, the more work it can perform. Example a Vehicle accelerating gains velocity and thus has an increase in energy. This is called Kinetic Energy. Also, when a Vehicle slows, it loses velocity, and thus loses energy. 1. REST ENERGY- ENERGY POSSESSED DUE TO AN OBJECT S MASS (Remember E=mc²) 2. KINETIC ENGERY ENERGY POSSESSED DUE TO AN OBJECT S MOTION (KE=wv²/2g) and (W=wfd) 2. POTENTIAL ENERGY - ENERGY POSSESSED DUE TO POSITION (PE=wh) ENERGY is transferred between different objects by doing WORK THE LAW OF CONSERVATIO N OF ENGERY ENERGY MAY BE NEITHER CREATED OR DESTROYED The most commonly used example is the pendulum: Determining Speed of Vehicles from the Damage received in Traffic Accidents We are now talking about the concept of WORK and ENERGY This concept is totally different than MOMENTUM. MOMENTUM can be used to determine pre-and post impact velocity it has speed and direction vector WORK or ENERGY is a scaler quantity- the product of the magnitudes of force and direction. WORK applied? SKID MARKS W=Fd and F=ma so W = mad v e = v I + ½ a t but d= v I t + ½ a t (V I = 0) so t = V e / a and d = ½ a V e /a(squared) DRUM ROLL PLEASE V = 2 a d or in MPH V = 30 f d SKID MARKS - WORK W=Fd and F=ma so W = mad v e = v I + ½ a t but d= v I t + ½ a t (V I = 0) so t = V e / a and d = ½ a V e /a(squared) Drum Roll Please: V = 2 a d or in MPH V = 30 f d 9

10 DAMAGED SUV Damage Profiles DAMAGED SUV LASER SURVEY DAMAGED SUV LASER SCAN TOP VIEW VEHICLE DAMAGE PROFILES DAMAGE PROFILE - SUV DAMAGE PROFILE - AUTOMOBILE DAMAGED AUTOMOBILE -1 ST SCAN DAMAGED AUTOMOBILE LASER SCAN TOP VIEW 10

11 What information is needed for an analysis using Crush? The Equation : C=a+bv where Mason 1972 Campbell s Equation : v= bo + b1c - which rearranged looks something like this C= Crush (in.) a = constant b = constant v= impact speed (MPH) ₂ ₂ E = ₂ W/5[5G + A/2(C1 + 2 C2 + 2C3 + 2C4 + 2C5 + C6) + B/6 (C1 ₂ ₂ ₂ ₂ +2C2 + 2C3 + 2C4 + 2C5 + C6 +C1C2 + C2C3+C3C4 + C4C5 + C5C6)] (1+ tan Ѳ) What do the variables mean? E = Energy dissipated G= A /2B 2 W= Width of the Crush Region A= The maximum force per inch of width which will not cause permanent damage (lb/in.) B= The spring stiffness per inch of damage width (lb/in ) 2 Ѳ = Angle between the principle direction of force and perpendicular. C1 through C6 Measurements of crush across the crush region! VEHICLE COLLISION-FULL IMPACT Postcollision vehicle positions! What direction was Vehicle 2 going? Occupant Dynamics A vehicle decelerates from 30 MPH to 0 MPH. The crush damages is 24 inches. How many g s will the vehicle develop. f= V² / (30(d)) = 900/30(2) = 15 g s The unbelted drivers head hits the windshield and puts a 4 indentation into the windshield. How many g s is the drivers head exposed to. f= V²/(30(d)) = (900)/(30 x.33) = 90 g s Would you believe the expert that opined that Vehicle 2 was turning left at the time? Note the time over which a collision occurs is important in determining the susceptibility to injury. 11

12 REACTION TIME Think in terms of perception and reaction Perception of a hazard. Initiation of avoidance maneuver. Olsen studies Human Factors Pedestrian Accidents Pedestrian Vehicle Impacts At collisions below 12 MPH Pedestrians sustain only minor injuries. Simple reaction time - RT = 1 sec to 1.5 sec AASHTO Complex reaction time RT > 1.5 sec, 2.5 sec?? Total Stopping distance = d (RT) + d (Braking) At speeds above 27 MPH Pedestrian collisions often end in a fatality (Wood, Otte) Why? KE = f (V²) Skippy the dummy- hit by car! Pedestrian Kinematics Wrap Projections (pedestrian and car at same speed, the a disassociation) Fender Vault Forward Projections (e.g. hit by a bus or van) Roof Vault (e.g. car goes under the pedestrian) Searle s The Trajectories of Pedestrians, Motorcycles, Motorcyclists, etc., following a Road Accident. Vmin = (2 µ g s )/(1 + µ²) V max = (2 µ g s ) Pedestrian Trajectory Equations Fall Equation : vi = df (g) / (2(dfG h)) where vi =initial velocity (ft/sec) g = acceleration due to gravity 32.2ft/sec² df = horizontal distance body traveled while falling (ft) G = percent grade (often use 0) h = height the center of mass falls (note negative if below take off positions Slide Equation ; vi = (ve)² - 2a ds where ve =end velocity (ft/sec) df = horizontal distance body traveled while sliding (ft) Other Equations : Rau et al, Toor and Arasewski, Simms et.al., Wood, PC Crash, Madymo V6.0 12

13 Pedestrian Accident Facts Leg Fractures first occur in healthy young adults at a speed of approximately 14 MPH. Multiple Severe fractures occur at speeds of approximately 25 MPH or greater. Leg fractures most likely occur from colliding with the bumper of a striking vehicle. The secondary impact of a pedestrian with the roadway can cause more severe injuries than the vehicle. Pedestrian Drag Factors See Searle Study 0.66? Sliding body 0.6 to 0.8 (Type of clothing has an effect) Tumbling body 1.0 Why are they different? How did this happen? Thank you! QUESTIONS? 13