Bicycle Collision Investigation

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BICYCLE COLLISION INVESTIGATION Roman F. Beck

Transcript of Bicycle Collision Investigation

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BICYCLE

COLLISION

INVESTIGATION

Roman F. Beck

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Copyright 2005 Roman F. Beck

All rights reserved. No part of this book may bereproduced in any form by any electronic ormechanical means (including photocopying,recording, or information storage and retrieval)without permission in writing from the author.

ISBN 0-615-12794-0

Additional copies of this book can be obtainedfrom the author on the Internet at:

www.beckforensics.comor

[email protected]

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TABLE OF CONTENTS

Acknowledgments iii

Author Biography iv

1. Introduction 1

2. Documentation 9Scene Measurements 9

Station Line 11Coordinate 12Triangulation 14Sideshot 16

Vehicle Measurements 19Photography 20

3. Environmental Factors 27Roadway Surfaces and Geometry 27Weather, Lighting and Obstructions 38Potential Roadway Hazards 41Roadway Evidence 42

4. Vehicle Factors 49The Bicycle 49

Bicycle Size 53Bicycle Types 54Frame Materials 68

Components 73Handlebars and Stems 74Forks 77

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Hubs 82Rims 84Tires 84Brakes 89Crank Arms 92Chainrings and Chains 92Saddles and Seat Posts 95Pedals 99Reflectors and Lights 99

Physical Evidence 101The Other Party 103

5. Human Factors 113Rider Size and Bicycle Fit 113Clothing 115Helmets 116Alcohol and Drugs 118Mental and Physical Deficiencies 120Perception-Response Time 121Visibility of bicyclists 123Injuries 125

6. Rider Kinematics 133Velocity 133Acceleration 142Braking 143Lean Angle 145End-Over 147

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7. Case Study 155At-scene Investigation 155Follow-up Investigation 165Investigation Results 166

8. Conclusions 177

9. References 181

10. Index 185

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1 – INTRODUCTION

With proper training and good technique, cyclingis one of the safest modes of transportation andone of the most rewarding forms of exercise.When recklessness and inattentiveness occur,death and serious injury are common for cyclists.Between 700 and 800 cyclists are killed each yearin traffic collisions throughout the United States.Although fatalities of pedestrians and motoristsoutnumber those of cyclists each year, they occuroften enough to warrant greater attention. Thistext is the only book solely about bicycle collisioninvestigation and is geared specifically to lawenforcement officers, risk managers, attorneys,and collision reconstructionists.

If the investigator has the right tools, the process ofinvestigation a bicycle collision can be simplifiedand the results can be more thorough. One of themost important analytical tools is an organizedframework. Perhaps one of the best frameworksavailable is the nine-cell matrix (Figure 1). Thenine-cell matrix is an analytical tool to help theinvestigator quickly classify a large amount ofinformation. This book is organized with the nine-cell matrix in mind, with the next three chapters ofthe book organized by environmental, vehicle,and human factors. These factors comprise oneaxis of the nine-cell matrix. The other axis of thisthree-by-three table is the time component, which

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Unlike with the station line and coordinate tech-niques, the investigator does not have to contendwith making perpendicular measurements (Figure4). As long as obtuse angles generally are avoided,the investigator can take accurate measurementswith a steel tape. This technique is recommendedfor serious injury and fatal collisions.

Sideshot This technique requires the use of sophisticatedinstruments such as a total station or a transit witha stadia rod or an electronic distance measuringdevice (EDM). By setting up the instrument andbacksight in known locations, evidence points canbe collected by taking sideshots (or foresight). Theinstrument determines the horizontal and verticalangles, and the rod-person provides the locationfor the instrument to measure the distance. Giventhese three sources of data (two angles and onedistance), the instrument or data collector thencan calculate the three-dimensional coordinatesfor the evidence points (Figure 5).

This equipment is fairly simple to use once theoperator has had sufficient formal training andexperience in set-up and operation techniques.With the notable exception of high-end robotictotal stations, two people are usually necessary foroperating the device. As long as the deviceremains level throughout the evidence collectionprocess, and the rod-person keeps vertical control,

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Figure 4. Documenting physical evidence with the triangula-tion technique and reference points (scale 1:1150).

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2 - Documentation

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Figure 12. Slurry-seal asphaltic cement concrete.

“chip-seal”, which has a layer of asphaltic con-crete underneath a rolled-in mixture of rock chipsand a viscous asphaltic emulsion (Figure 13).Portland cement concrete roadways also vary inthe size of the aggregate and the roughness of thefinished surface (Figures 14 to 16). Until trafficremoves them, the “fines” visible in Figure 15 mayinitially reduce the potential drag factor.

Although many bicycle collisions occur onPortland cement concrete sidewalks, the maintype of roadway surface where bicycle-vehiclecollisions occur is asphaltic cement concrete .Because roadway surfaces wear unevenly, theinvestigator should photograph the actual surface

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3 - Environmental Factors

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Figure 25. A nine-cell matrix accounting for some of theenvironmental factors identified in a nighttime collisionbetween a bicycle and a motor vehicle (see Chapter 7).

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Pre-collisionEnvironmental

Factors:Dry sand-and-

seal asphalt cement concrete

roadway in good condition,cloudy visibility,possible viewobstructions,

dark-no street-lights, roadway

striping

CollisionEnvironmental

Factors:No bicycle tirescrub marks,

no motor vehicle skidmarks, no

bicycle rim andaxle scrapes, nomotor vehicle

headlamp debris, but some

cyclist’s belongings

Post-collisionEnvironmental

Factors:No motor

vehicle skidmarks,

cyclist’s clothingand food

debris, scrapeson bicycle from tumbling and

sliding on roadway

Pre-collisionVehicleFactors

CollisionVehicleFactors

Post-collisionVehicleFactors

Pre-collisionHumanFactors

CollisionHumanFactors

Post-collisionHumanFactors

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Figure 28. The Cyclo-cross usually is equipped with slightly-knobby and narrow 700mm wheels, multiple-speed gears,and drop handlebars. Cantilever brakes (lower right) are themost common, but some have disc brakes (lower left).Although similar in appearance to a Road/Race bicycle, theCyclo-cross differs in that the fork is usually straight, ratherthan curved, and the frame is a size or two smaller to easedismounting. The fork, brakes, and stays are usuallydesigned for optimum mud clearance. The titanium modelabove was designed with 73-degree seat and head tubes,which are common angles for this bicycle type.

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Figure 40. The fracture in this steel alloy tube is about 1/8”(3 mm) to the right of the weld, and is an acceptable fractureas a result of excessive force.

(see Figures 41 and 42). These weld and tubebreaks can have catastrophic consequences to therider, who is sometimes unaware of pre-existingstress fractures. If any type of weld or tube failureis suspected, the frame should be inspected by areputable framebuilder.

Sometimes frame and component cracks are notimmediately obvious, and are only discoveredduring regular maintenance or part replacement.Figure 43 depicts a crack in the chain stay of analuminum road bicycle frame. Because high-end

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Figure 54. Cracked rim as a result of excessive spoke tension.Although not impossible to occur at the front wheel, thisevent is most common on the right (drive) side spokes of therear wheel, because of the rear hub’s rotational force trans-mitting from the spokes to the rim.

Figure 55. Blown out aluminum rim as a result of carelessoverinflation, and could have been catastrophic.

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Figure 74. The upper image depicts a bicycle pedal imprinton the front bumper cover of a minivan involved in a right-angle collision, while the lower image depicts anhead/shoulder imprint at the top of the windshield and lead-ing edge of the roof. From the driver’s view, the bicycle wastraveling from left to right. The location of the damage in thelower image is further inboard from the driver’s side than thelocation of the damage in the upper photo, indicating thatthe bicycle was moving at the time of impact.

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especially to narrow ones. Because many colli-sions between cyclists and motorists occur at theright side of the vehicle, the right “A” pillar mayobstruct the motorist’s view of the cyclist. If theinvestigator suspects that such an obstruction, thenhe or she should position a camera at themotorist’s eye height and take photographs of the“A” pillar from within the vehicle. Note the posi-tion of the driver’s seat in the track. Also note anypotential obstructions within the vehicle, such as adirty windshield or fuzzy dice. This is also anappropriate time to inspect potential distractionsas cell phones, food, maps or paperwork.

InjuriesCyclist injury patterns are often similar to those ofpedestrians. Because the cyclist has little or nocrash protection from the bicycle, the type andseverity of injuries is usually a function of momen-tum. This positive correlation simply suggests thatthe greater the momentum, the more severe theinjury. Perhaps the most serious injuries to cyclistsoccur at the head, usually a result of direct contactwith the windshield, hood, or roadway. A headand shoulder strike to the windshield of a motorvehicle traveling with a closing velocity in excessof 40 miles per hour (64 kilometers per hour)often results in fatal injury, even if the rider waswearing a helmet. However, even in low speedcollisions a helmet-wearing cyclist can sustain fatalinjury from ground contact.

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Figure 82. Side mirror view of bicyclist. Distances from rightmirror: 100 feet (30.5 meters), 75 feet (22.9 meters), 50 feet(15.2 meters), and 25 feet (7.6 meters). Images courtesy ofHarris Visibility Studies.

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When the lateral acceleration factor and pathradius are known, the formula for determiningvelocity is:

(where “a” is acceleration in feet per sec-ond per second, “fL” is lateral accelerationfactor, “R” is radius of the path in feet, and“V” is velocity in miles per hour).

For example, a cyclist turns right at an intersectionthat has a raised Portland cement concrete side-walk with a radius of 25 feet (7.6 meters). At thiscurve the minimum turning radius is about 27 feet(8.2 meters). Using the above equations, the bicy-cle’s speed is 10.4 miles per hour (16.7 kilometersper hour) at a lean angle of 15 degrees. At a leanangle of 20 degrees, the speed is 12.1 miles perhour (19.5 miles per hour) (Figure 89).

End-OverBecause of the potential severity of the end-overor pitch-over collision, and because it can occur inboth solo and motor vehicle collisions, further dis-cussion is warranted. The end-over is usually theresult of one of more of the following four reasons:(1) hard front braking, (2) a frontal impact with anobject that is more rigid than the front wheel, (3)a fallen front wheel (often from not securing the

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Figure 90. A mountain bicyclist traveling at about 22.5 milesper hour (36.2 kilometers per hour) applies only the frontbrake. Once the front wheel is nearly locked, the rear wheelstarts to lift up. At about 0.20 seconds the rider really has nochance to recover. At about 0.33 seconds he releases thebrake and prepares his right hand, and then his left hand forthe landing. The cones are spaced in 25-foot (7.6-meter)intervals, the grade is about -2%, and the test surface isdepicted in Figure 17 on page 32.

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Figure 102. Impact alignment for the Brian Young collision.

the right of the license plate. This evidence givesthe necessary information for alignment at maxi-mum engagement. Initial contact may haveoccurred with the bicycle about one foot (30 cm)closer to the driver’s side of the vehicle.

In reviewing the role of view obstructions, BrianYoung should have been able to see oncomingheadlights, even though his brother was on hisright. Although the vehicle in lane number twomay have been easier to see than the car in lanenumber one, both cyclists were probably aware ofoncoming traffic. The “A” pillar obstruction for thedriver is a less complicated matter. Given that thecyclists were stopped as the Pontiac approached,the motorist would have seen them through thewindshield (not through the left door window) asthe headlights illuminated the bicycles’ reflectors.Oncoming headlights may have also backlit hisview of the cyclists.

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9 – REFERENCES

AASHTO Guide for the Development of BicycleFacilities. American Association of State Highwayand Transportation Officials, Washington, DC,1999.

Baker, J. S. and Fricke, L. B. The Traffic-AccidentInvestigation Manual, Ninth Edition. NorthwesternUniversity Traffic Institute, Evanston, IL, 1986.

Barnett, J. Barnett’s Manual: Analysis andProcedures for Bicycle Mechanics, Fifth Edition.VeloPress, Boulder, CO, 2003.

Beck, R. F. Mountain Bicycle Acceleration andBraking Factors. Proceedings of the FourteenthCanadian Multidisciplinary Road SafetyConference, Ottawa, Canada, 2004.

Burns, M. Medical-Legal Aspects of Drugs.Lawyers and Judges Press, Tucson, AZ, 2003.

Casteel, D. A. and Moss, S. D. Basic CollisionAnalysis and Scene Documentation, SecondEdition. Lawyers and Judges Press, Tucson, AZ,1999.

Eubanks, J. J. and Hill, P. F. Pedestrian AccidentReconstruction and Litigation, Second Edition.Lawyers and Judges Press, Tucson, AZ, 1999.

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Dreyfuss, H. The Measure of Man. WhitneyLibrary of Design, New York, 1967.

Faria, I. E. and Cavanagh, P. R. The Physiology andBiomechanics of Cycling. John Wiley & Sons, NY,1978.

Forester, J. Bicycle Transportation, Second Edition.MIT Press, Cambridge, MA, 1994.

Forester, J. Effective Cycling, Sixth Edition. MITPress, Cambridge, MA, 1993.

Fricke, L. B. and Baker, J. S. Drag Factor andCoefficient of Friction in Traffic AccidentReconstruction. In Traffic AccidentReconstruction: Volume 2 of the Traffic AccidentInvestigation Manual, First Edition. NorthwesternUniversity Traffic Institute, Evanston, IL, 1990.

Garriott, J. C. Pharmacology and Toxicology ofEthyl Alcohol. In Medicolegal Aspects of Alcohol,Third Edition, edited by J. C. Garriott, pp. 35-63.Lawyers and Judges Press, Tucson, AZ, 1996.

Harris, J. L., Harris, J. L. Jr., Beck, R.F. BicycleVisibility in Right-Side Mirrors. Unpublished man-uscript, 2005.

Hayduk, D. Bicycle Metallurgy for the Cyclist.Johnson Publishing, Boulder, Colorado, 1987.

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Institute of Transportation and Traffic EngineeringBikeway Planning Criteria and Guidelines.University of California, Los Angeles, 1972.

Li, G. and Baker, S. P. Alcohol in Fatally InjuredBicyclists. Proceedings of the Thirty-SeventhAnnual Association for the Advancement ofAutomotive Medicine, pp. 129-141, San Antonio,TX, 1993.

Martin, J. C., Milliken, D. L., Cobb, J. E.,McFadden, K. L., and Coggan, A. R. Validation ofa Mathematical Model for Road Cycling Power.Journal of Applied Biomechanics 14:276-291.Human Kinetics Publishers, Inc., 1998.

Olson, P. Driver Perception-Response Time. InHuman Factors in Traffic Safety, edited by R. E.Dewar and P. L. Olson, pp. 43-76. Lawyers andJudges Press, Tucson, AZ, 2002.

Skorcz, J. L. Fundamentals of Cycling Posture.Bicycle Size and Positioning. Barnett BicycleInstitute, Colorado Springs, CO, No date.

Virkler M. R. and Balasubramanian, R. FlowCharacteristics on Shared Hiking/Biking/JoggingTrails. Transportation Research Record 1636:43-46, 1998.

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Watson, W. A. and Garriott, J. C. Alcohol andMotorcycle Riders: A Comparison of Motorcycleand Car/Truck DWI’s. Journal of Veterinary andHuman Toxicology 34:213-215, 1992.

Wilson, D. G. Bicycling Science, Third Edition.MIT Press, Cambridge, MA, 2004.

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10 – INDEX

A“A” pillar 125, 162, 177AASHTO 149abrasion 23, 89, 95, 101, 102, 106, 128, 155, 162, 167acceleration 56, 111, 120, 137, 146, 149, 151, 157, 176,179Adobe Photoshop 24aerodynamic drag 39, 114, 137-139, 143, 176alcohol 113, 118-121, 131, 161ambient light 40angular size 124. see Harrisanxiety 119Archer, Jeff. See firstflightbikes.comArizona 117arm length 54. see fitasphaltic cement concrete 27-30, 38, 86, 89, 99, 147,159, 164

chip-seal 29, 30sand-and-seal 28, 46slurry seal 27

Australia 116, 138axle 51, 77, 101

BBaker 4, 24, 36, 119. see Frickebalance 119, 120Balasubramanian 138Barnett 3barometric pressure 143Beachcomber 62, 64Beck 32, 146, 148beckforensics.com 6, 7, 157bicycle lane 40bicycle maintenance 3. see Barnett

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bicycle messengers 120bicycle size 53, 54bicycle types 54, 55, 71biological material 44blood 9, 42BMX 32, 54, 55, 63, 67body armor 61bottom bracket 9, 52, 54, 59, 71, 92, 112brakes 52, 56, 57, 61, 64, 84, 89, 91, 112

cantilever 57coaster 91disc 38, 52, 57, 61, 91failure 103lever 122, 152, 153V brake 52

braking 137, 143, 147-149, 151-153, 155, 157efficiency 38, 84, 91power 38, 39

brightness 115bumper 105, 106, 111, 161, 162, 170, 176, 179bunny hop 41Burns. See alcohol

Ccable tension 91cadence 52, 92, 139, 143, 176California 113, 116

Davis 138California Vehicle Code 4, 178Casteel 3. see MossCavanagh 138. see Fariacenter of gravity 66chain 51, 67, 70, 71, 73, 92, 94, 96, 102, 170

outer plate 96, 97chain stay 56, 70, 71, 73, 170chainring 95, 51, 52, 54, 66, 92, 94, 102, 139, 140, 142,144, 157, 170, 174, 175

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Chicago 52children 54, 55, 67, 146chord 36. see middle ordinateChristini 139cleat 99clipless 52, 62, 99clothing 113, 115, 116, 124, 131, 162, 179collision scrub mark 43component failure 5compound curve 35computer 52, 139construction level 36Consumer Product Safety Commission 5contrast 115, 124contusion 128coordinate 3, 10-12, 15, 16, 166crack 70, 72, 73, 80, 84, 92, 93, 97crank arm 51, 92, 93, 139crown 34, 36, 159cyclo-cross 44, 57, 81

Ddebris pattern 9demagnification 124depressants 118derailleur 51, 58, 92, 102, 103, 170detection 119, 122-124down tube 9, 51, 52, 71, 74drag factor 29, 34, 36-38, 147, 149, 159Dreyfuss 122drive-wheel size 139, 140, 142-144drug 16. see alcoholdrug recognition expert. See alcohol

Eedge of roadway stripe 11elderly 146

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electronic distance measuring device 16end-over 58, 66, 77, 83, 151, 153, 157Eubanks 4. see Hillevidence match 99eye height 40, 125

FFaria 138. see Cavanaghfatigue 72, 93, 119fender 109final rest positions 108, 109firstflightbikes.com 55fit 19, 53, 54, 62, 67, 113-115, 117, 131flexibility 54, 62Forester 145fork 57, 59, 61, 67, 77-82, 101fracture 68-72, 93fracture overload 68framebuilder 70, 72Freeride 59, 60, 61Fricke 4, 24, 36. see Bakerfront axle 77front overhang 170Full-suspension Mountain 59-61

GG-Analyst 38Garriott. See alcoholgear lever 77Gear Matrix 140, 142, 143, 174gear ratio 140, 143, 144, 176glare 39gloves 116gouge 9, 23, 99, 101grade 34-36, 143, 145, 154, 157, 159grate 41

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Hhallucinogens 118halogen 99, 107handlebar 51-53, 56-64, 74-77, 92, 101, 114, 115, 139Hard-tail Mountain 59, 60Harris 124, 126. see visibilityHayduk 68, 112head tube 9, 51, 54, 63, 64, 71, 76, 107headlight 40, 161, 178

filament 40headset 51, 77, 107

race 79heart rate 52helmet 43, 53, 61, 116, 117, 125, 156, 161high-wheeler 49Hill 4. see Eubankshood 104, 109, 125, 170hub 51, 77, 81, 82, 83, 85, 92, 152Hybrid 62

IIllinois 117inhalants 118injury pattern 128, 131inseam 53, 54, 113, 114, 170

Kkinematic analysis 137Klunker 59, 64. see Ritcheyknee 114, 116

LLeague of American Bicyclists 5, 177lean angle 137, 149-151lever play 89Li 119

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lighting 27, 38, 39, 47lights 38, 40, 46, 47luminance 101

Mmaximum coasting speed 143, 145, 157maximum engagement 177mechanical failure 49mental deficiencies 113, 120, 121, 131, 161metal clips 99middle ordinate 36. see chordMiller, Don Show 5mirror 124-126. see visibilityMongoose 169, 174, 175Moss 3. see Casteelmotocross 63, 116motorcycle 3, 55, 65, 74, 89, 119

Nnarcotics 118. see GarriottNew Zealand 116nighttime 24, 39, 40, 46, 115, 116, 130nine-cell matrix 1, 2, 9, 45, 46, 103, 111, 129, 130, 149,179, 180Niterider 101. see HalogenNorthwestern University Traffic Institute 36. see Baker

Oobtuse angle 16Olson 121. see perception-response timeoversized bicycle 67, 115oxidation 72, 75

Ppad alignment 89. see brakespad wear 89, 90

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paint 43transfer 21, 23, 106

PCP 118pedal 51, 52, 59, 62, 92, 93, 99-101, 104, 105, 114, 115,122, 123, 161, 170, 176pedestrian 103, 123-125pedicab operators 120perception-response time 120-123, 130, 131, 152, 176,179photogrammetric 19photography 4, 24, 25, 29Photomodeler 25physical deficiencies 113, 120, 121physical evidence 4, 7, 9, 13, 15, 17, 18, 20-23, 25, 27,42-44, 84, 101, 103, 104, 108, 137, 141, 146, 149, 157,162, 165, 169, 180pin 96, 97pitch-over. see end-overPortland cement concrete 27, 29-31, 38, 147, 151power 49, 52, 82, 92, 139Presta Valve 87prosthetic limb 121

Qquick-release 77, 81, 82, 151

Rrailroad tracks 41, 42rain 27, 31, 38Razor™ scooter 3, 55rear suspension 60, 61, 71, 169recumbent 66reference line 12, 14reflector 38, 40, 99, 160, 161, 171, 177, 178reflex reaction 152rider dynamics 3, 7rider kinematics 2, 137, 139, 141, 143, 145, 147, 149,

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151, 153, 155, 157rider visibility 99rigid mountain 50, 59, 60rim 51, 52, 56, 64, 84-86, 90, 91, 102, 109, 110, 171,179Ritchey 59road/race 56-58, 66, 78rollmeter 10

Ssaddle 51, 95, 98, 102, 114, 170, 173

height 19Schrade valve 87Schwinn 55, 59, 64, 65

Excelsior 59, 64Stingray 55, 65

scrape 23, 84, 99, 101, 110scratch 77, 99, 101seat post 51, 54, 62, 95, 98, 99, 114seat stay 170, 172, 176seat tube 51, 54, 56, 58, 71, 114seat. see saddleserial number 52, 112Serotta 114shadows 39sideshot 10, 11, 16, 18signage 27, 40, 47skid mark 44, 87, 89, 108, 137, 147, 179Skorcz 115snow 27, 38solo collision 38Southern California 63Speed Matrix 143, 144, 175spoke 82, 84, 85, 102, 152, 153sprocket 52, 94, 102, 139, 140, 142, 144, 157, 170, 174,175Stalker ATS 38

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stanchion clamp 80stand-over height 54, 114station line 3, 10-13, 16, 166steel tape 10-12, 14, 16, 166stem 51, 62, 63, 74, 76, 77, 114, 170, 173stepping 10, 11stimulants 118, 120Stingray 55, 65stopping distance 38, 120straps 99super-elevation 34-36, 159SwXng 64

Ttaillamps 40tandem 55, 66tensiometer 82tension 82, 84, 85, 91, 102time trial 58time-distance analysis 137tire 51, 52, 58, 84, 87-89, 101, 102, 108, 143, 146, 149,152, 153titanium 57, 59, 60, 67-69, 78, 81top tube 19, 51, 53, 54, 58, 65, 106, 107, 114, 170total station 3, 10, 16, 19touring 55, 56track 55, 64triangulation 3, 10-12, 14, 17triathlete 58twilight 27, 39, 40

UU-brake 63UCLA 138undercarriage 23United States 138utility vault 41

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Vvanadium 69V-Box 38velocity 137-140, 143, 150-152, 170, 176vertical curve 3, 35view obstruction 40, 46, 103, 104, 177

transitory 40transitory-fixed 40

Virkler 138visibility 36, 39, 40, 46, 113, 115, 116, 121, 123, 124,126, 131visual estimation 10-12

Wwarning signs 35, 40watt 146weather 27, 38, 47website 55weld 59, 68, 69, 70, 72, 73

contamination 68, 72TIG-welding 68

wheelbase 56, 170Wilson 3, 38, 149wind 27, 39, 47

crosswind 39headwind 39tailwind 39

windscreen 66, 139windshield 104, 105, 109, 111, 125, 130, 153, 156, 161,162, 170, 177, 179WNNX. see Miller, Don Show

Yyaw mark 9

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