Bicycle Crash Investigation

By Kirby Beck, PCI #002T
Coon Rapids (MN) Police Department (retired)

If a bicycle crash results in a death or serious injury, assume that the incident will result in a lawsuit. Many people on both sides of the case will read your reports and examine the results of your investigation. They will have many opportunities to critique your work.

After reviewing a number of crash reports by officers and crash reconstruction experts, it is apparent that many important factors involved in bicycling are either unknown or unconsidered and quite often undocumented by crash investigation professionals.

The state of the art in specialized bicycle crash investigation and reconstruction is rudimentary at best. Focused training in bicycle crash investigation is rare, if it exists at all. In virtually every state, bicycles have most of the same rights and responsibilities as motor vehicle operators. Many officers don’t seem to know, or care, that they do. Training in bicycle traffic law is virtually non-existent in police academies and crash investigation courses.

Unfortunately, many serious road cyclists know and understand traffic laws regulating bicycles far better than most street cops. Officers who have received quality bike patrol training, such as the IPMBA Police Cyclist™ Course, have been trained in the legal status of bicycles in traffic, proper and legal lane use, and other pertinent provisions.

When investigating a bicycle-vehicle crash, it may be a good idea to involve a trained bike patrol officer to help get a comprehensive perspective as to the bicycle-related factors and conditions involved. Criminal charges may be warranted. An officer knowledgeable in bike law could be a victim cyclist’s best advocate, or a legal opponent, providing the details for fair prosecution.

Some states don’t require, or even allow, a police crash report unless the crash involves a motor vehicle. Yet, it is quite possible to have a serious or fatal crash involving a lone cyclist, two or more bikers, or even a cyclist and a pedestrian. Since these don’t involve a motor vehicle, none would be reported on an official state or FARS crash report form. These incidents would be classified as a public accident of some sort. The obligation for a thorough and detailed investigation is no less important.

The physics affecting bicycles and motorcycles are similar in most ways. When examining drag factors, braking efficiencies and percentages, as well as wheel tracking, those qualified to assess those dynamics can use the same general factors. Like a motorcycle, a bicycle is a single-track vehicle. Unlike a motorcycle, a bicycle is far more affected by weather and surface conditions. Both rely totally upon the balance of its rider to remain upright.

Despite the rider’s best efforts, more things can happen to cause a bicycle to fall or crash to the ground. Balance is easier to maintain when the bicycle is traveling faster, and is harder to maintain while going slowly. There exists somewhat of a gyroscopic effect with rapidly spinning wheels, and to a lesser extent, rapidly pedaling legs. When its pedals are powering a slow moving bicycle, the bike’s center of gravity drops from the top of the saddle to closer to the bike’s crank set and bottom bracket. The center of gravity moves up higher when it is not being pedaled.

Balance is primarily maintained through minute movements of the front wheel. Sudden and unexpected movement of the handlebar or the front wheel can cause the bike to rapidly lose balance and fall. If the front tire strikes an object laterally, such as a hole, the side of a curb, the gap or grade difference between asphalt and concrete curb, or the side of another bike tire, it diverts the balance, causing what is known as a diversion crash.

The diversion crash can also happen should the front tire get trapped in the gap between road surface and concrete gutter apron, or in the gaps of a diagonal railroad crossing. It results in a near instantaneous fall. It is only through great luck and skill that a cyclist can prevent such a result when their balance is diverted with lateral front tire contact. A diversion crash may explain a sudden and unexpected fall. There may not be evidence on the bike, but other evidence of a causation factor might be located nearby.

The process of balancing a bike also affects a bicyclist’s rear profile. The widest part of a bicycle is its handlebars. Few handlebars are wider than 24 inches. The widest part of the profile may indeed be the rider, especially across their shoulders. The process of balancing the bike, and making the necessary movements of the front wheel, causes it to move subtly from side to side.

This side-to-side movement is more obvious at lower speeds. This normal side-to-side motion widens the cyclist’s profile, or space used, to somewhat wider than his shoulders. In reality, the bike needs a “wobble lane” width that is approximately three-feet wide.

Weather is a factor that affects cyclists. Rain or snow can certainly influence tire traction. Wet rims will reduce the effectiveness of certain types of brakes. Rain can even hamper a cyclist’s ability to see and be seen. The most under-recognized effect of weather on cyclists might be that of wind. Riding into a headwind can be very distracting. It requires extra effort to pedal into a headwind. The extra effort increases both mental and physical fatigue.

Riding into a headwind also makes it difficult to hear all but the noisiest vehicles approaching from the rear. Unless a cyclist looks behind him when moving out into traffic, he might not realize a vehicle is bearing down on him.

While crashes involving cyclists being struck by motorists (overtaking) from the rear are statistically quite rare, they are often the most deadly. While they are the most feared bike crash, they generally make up less than 10% of all bike versus motor vehicle crashes.

When analyzing these “overtaking” crashes, it is important to try to determine if the cyclist was riding a straight line in a roadway location he legally belonged, or if he was swerving (unexpectedly) laterally to avoid something like a hole or obstruction. Perhaps he swerved recklessly for no apparent reason at all.

Most fatal overtaking crashes occur at night. This makes it crucial for investigators to determine if the cyclist was in the proper and legal lane position. It’s also essential to determine if the cyclist was using legally required lights and reflectors or any other devices or clothing to enhance his visibility.

In daytime, a headwind may prevent a cyclist from hearing vehicles approaching from the rear. At night, a cyclist would usually notice headlights overtaking him, even if a headwind prevents him from hearing it.

When investigating a serious bicycle crash, it is important to determine and document the wind speed and direction. That may prove or disprove a factor in the incident. A nearby fire station or school may have a local weather station that can provide that close-to-the-scene information.

A final weather factor that can be particularly dangerous is the glare from the sun. The blinding rays of the sun, especially when combined with a dirty or streaky windshield, can make seeing a bicyclist nearly impossible.

This problem is worsened by the fact that most motorists aren’t conditioned to expect or look for cyclists. Most drivers are conditioned to search for cars, trucks and buses that will endanger them or their car if they pull out in front of them. With a bicycle being a narrow single-track vehicle, operating in or near traffic, they are particularly vulnerable to the effects and hazards of glare. Documenting any glare as accurately as possible should be a goal if glare is suspected of being a factor.

Environmental Factors
When a bicycle and motorists are sharing the same space on a roadway, the width of the traffic lane, vehicles and shoulder becomes crucial to measure and document. Normally, bicyclists are expected to ride on the shoulder, in the same direction as adjacent traffic, if a shoulder exists and is in rideable condition.

Exceptions to shoulder riding exist both legally and in practice. Cyclists can leave the shoulder and even take the (traffic) lane, if the shoulder is blocked or unrideable, if the cyclist is making a left turn, if he is avoiding an obstruction or hazard, or when he passes a parked car or a slower moving vehicle.

In the event of a serious bike-related crash, the investigator needs to determine if the cyclist should have been on the shoulder and if the exceptions to shoulder riding were present. Inspect and document the width and condition of the shoulder, if one exists. Look back at least one block prior to the crash scene. Was there a reason why the cyclist may have had to leave the shoulder and use the traffic lane?

In incidents where the cyclist shared the traffic lane with motorists, determining the various widths becomes more important. How wide is the traffic lane? How wide is the motor vehicle involved? Remember that the cyclist needs a “wobble lane” at least three feet wide. Can the two operate in the traffic lane two abreast while allowing a safety cushion of roughly three feet?

Several states have even mandated that vehicle operators pass no closer than three feet from a cyclist. By law, if the lane is too narrow for both to operate safely side-by-side then the motorist has to slow and yield the lane to the cyclist. Check your own state’s statutes, but most states restrict their “impeding traffic” statute to the operators of motorized vehicles. In most cases, a bicyclist, operating legally otherwise, is exempt from an impeding traffic law!

Bike lanes are found in many cities. Bike lanes are part of the roadway and all related laws would apply. Cyclists in a bike lane, wishing to make a left turn, find themselves in a bit of a quandary. If they make it from the bike lane itself they are essentially making a left turn from the far right lane of the roadway. This maneuver results in one of the most frequent types of car/bike crashes.

If a motorist made this maneuver, it would be considered an illegal and unsafe lane change, of course! Many cyclists choose to leave the bike lane and use the traffic as any other vehicle would. Other, less confident cyclists stop at the intersection and make a pedestrian-style street crossing. Occasionally bike lanes are shared with parked cars, and conflicts are dangerously increased between cyclists, motorists and activity related to parked cars.

Sidewalks & Bike Paths
Another factor in the riding environment is cyclists riding on sidewalks or bike paths. In some states, cyclists are prohibited from riding on sidewalks, or may only be forbidden from riding in business districts, where conflicts with pedestrians are dangerous. In other states, where they are permitted on sidewalks, they are legally defined as pedestrians, and subject to the same rights and responsibilities as pedestrians.

Most police aren’t any more knowledgeable of pedestrian laws than they are of bicycle laws. Investigators should review their Traffic Code and ordinances for pertinent regulations on cyclists and pedestrians using sidewalks and bike paths.

A growing number of communities are building bike paths adjacent to roadways for cyclists and pedestrians to use. They often parallel streets much like sidewalks. Both bike paths and sidewalks provide a perception of safety to their users. Statistics, however, show that they are usually no safer where they intersect roadways and, in many cases, they prove to be more dangerous.

One of the reasons they are more dangerous is that sidewalk and path cyclists are often legally defined as pedestrians, exempt from the usual vehicular traffic rules and laws. Paths and sidewalks are likely not within the scope of the traffic code. Cyclists can ride both directions, not necessarily the same as adjacent traffic.
In most cases traffic controls, like stop signs and semaphores, don’t apply to path users. In many cases they intersect streets at a location set back from the main intersection. Having cleared the intersection, motorists aren’t conditioned to scan bike paths or sidewalks. They don’t expect anyone to approach from both directions and at speeds much faster than a person can walk.

This junction of two systems, one for motorists, one for pedestrians, results in many conflicts with associated collisions and casualties. In addition, many of the bicyclists who operate on sidewalks and paths are children who have little to no understanding of traffic rules and principles. Few can imagine that what they do on their bike can get them killed or seriously injured. Those factors combine to make the intersection of roadways with bike paths and sidewalks very dangerous and legally confusing places to be.

Specific Concerns Unique to Bicycles
No one would do a crash report without recording the make, model and license number of a motor vehicle, yet bikes are often listed as simply a “bike.” Record and photograph the make, model and serial number of the bicycle. Serial numbers are found in one of three locations: under the bottom bracket where the pedals are located, on the (rider’s) left side of the top tube below the handle bars, and on the left side “dropout” where the rear hub attaches to the frame. On some high-end BMX bikes, it may be on the inside of the dropout.  If there are more than two sets of numbers use the set on the left side or the forward most.

Frame Size
Bike size is often listed, incorrectly, by the diameter of its wheels. For example, BMX type bikes have 20-inch wheels, and mountain bikes have 26-inch wheels. Wheel size can be found by checking the side of the tires, but bikes are more accurately sized by measuring their frames. That measurement might be found on a sticker on the frame, but don’t expect it.  You will most likely have to measure it yourself.

A frame is measured from the center of the bottom bracket to the top of the seat tube. On mountain bikes, BMX and most other bikes, the measurement is listed in inches. Road bikes, or racing type bikes, have their frames and wheels measured in centimeters.

Knowing the frame size may help an investigator determine whether the bike was too large for the rider. Riding a bike that is too large is quite dangerous and may cause control problems. It may also be a violation of the law. A rider must be able to stand over the bike’s top tube while standing flatfooted. If the rider was killed or seriously injured, the stand-over test is obviously impossible. Knowing the frame size may make it possible to determine whether it was safe by using the rider’s measurements. Legally, the height of the frame is ultimately at issue, not the height of the saddle.

Bicycle tires have only a very small portion of rubber on the road at any one time. Even the best tires provide an actual surface area, on each tire, of approximately half the size of a dime. Most bike tires have even less area. That portion of the tire surface is the sole point of traction for acceleration, braking and turning. It is easily affected by wet or slippery surfaces.

Traction is particularly vulnerable when trying to brake hard and turn at the same time. The small surface area contacting the pavement cannot accommodate both actions simultaneously, and the loss of traction often results in a fall.  Lugged or knobby off-road tires are designed to increase traction and surface area on non-paved surfaces.  On pavement, however, the surface area of the tire is actually less and traction is poor, especially when the surface is wet.  Tires play a significant role in the cyclist’s ability to maintain traction and balance. Inspect and photograph the tires. Document their size, type and condition.

Accessories and Clothing
Any and all accessories mounted on the bike should be photographed. Any lights, reflectors or other safety devices should be documented. Some accessories or parts may have broken off and lay nearby. These, too, should be documented and photographed as part of the investigation. Virtually every state in the United States requires bicycles to be equipped with – and use – a headlight if operated on a roadway at night or in low-light conditions.

Several states also require that bikes use a taillight, not merely a reflector, when operated at night.  Check state statutes to see precisely what is required in your locale. If you are unfamiliar with the law, you may not know what needs to be verified and documented.

Some bikes are equipped with mirrors, and some cyclists use mirrors mounted to the side of their helmets. Bike mirrors in the U.S. need to be mounted on the left side of the bike to be effective in traffic. Bike mirrors are small. They allow the cyclist to see if a vehicle is approaching, but may not accurately depict distance, closing speeds and other important information. The cyclist should still look over his shoulder to get more precise information. Inexperienced cyclists may tend to swerve toward traffic when looking over their left shoulders. Statements from witnesses may indicate such movement if it is suspected.

Personal entertainment devices, such as MP3 players and iPods, are frequently used by cyclists, nearly all of whom use earplugs in both ears.  It is not uncommon for them to be quite loud. Just as a strong headwind can make it difficult to hear vehicles approaching from behind, these devices make it nearly impossible to hear oncoming traffic. In a few states, they are illegal to use on a roadway.  Because hearing is an important sense for surviving in traffic, use of these devices on a roadway is particularly dangerous. If the cyclist was using them at the time of the crash, it should be documented.  If possible, note and document the volume level.

Brakes & Other Components
Bicycles today have a variety of brake types. They run the gamut from pedal-activated coaster brakes to high-end hydraulic disc brakes. The function of brakes should be tested, if possible. Check and document the condition of all components of the brakes.  Are all of the cables and brake blocks intact and connected?  Is it possible to tell if they are adjusted correctly?  Keep in mind that statutes in every state require bikes operating in or near traffic to have functional brakes.

A factor that may affect children is the size and adjustment of brake levers.  Occasionally, kids ride bikes that are too big for them. Their hands may not be able to physically reach the brake levers in order to activate them. Investigators should question that possibility if a child and hand brakes are involved in a situation in which the bike didn’t stop when it should have.

Assess the overall mechanical soundness of the bike.  If the frame, wheels or components are broken, it may be possible to tell if the damage is fresh or not.  If there is any doubt, take the bike to a professional bike mechanic for an opinion about the bicycle in all mechanical aspects. A professional bike mechanic may be able to tell you if the damage was pre-existing, and if so, if it could have caused the cyclist to fall.

Bike mechanics can also examine brakes and other components to determine their functionality before the crash. They may have experience with that particular model and its idiosyncrasies. Occasionally bicycle companies or the Consumer Product Safety Commission issues recalls or warnings about particular bikes or components. A professional mechanic could share that info and bring another perspective to your investigation.

Pre-Crash Speed
Establishing the bike’s pre-event speed is important, but may be difficult to determine.  If the bicycle is a multi-speed model, photograph and document the chain position, both front and back.  By looking at the gear combination, the type and quality of the bike, together with other factors, a cycling expert may be able to make a reasonable estimate of the rider’s speed.

Statements from witnesses regarding the rider’s body position on the bike, pedaling cadence, and perceptions of speed are all important to document.  For example, a bike ridden slowly in a very high gear will be difficult to pedal and may be somewhat wobbly.

Skilled cyclists use their gears more efficiently and they regularly ride with a higher pedaling cadence. Less skilled cyclists tend to shift less and ride in gears that make them work too hard when pedaling. Each gear combination has a unique “stride length.” Each revolution of the pedals causes the bike to travel a certain, constant distance.

Higher gears travel a longer distance with each revolution of the crank than do lower gears. By counting the number of teeth on the rear cog and front chain ring that the chain is found in—and noting the tire size—it is possible to determine the stride length used by the rider. It then becomes important to ascertain from witnesses whether the cyclist was pedaling quickly or slowly.

It isn’t unusual for a crash to knock the chain completely off of the drivetrain.  It is more unusual for the chain to be bumped securely onto a different set of cogs.  While gear position is not a foolproof means of determining the cyclist’s speed, it is a very good piece of information to determine and document.

Secure the Bike
In fatality cases, and others that will likely end in criminal or civil court, it is always best to secure the bicycle in the condition it was found.  Despite the number and quality of photographs, it is always best to have the actual bike to refer to and bring into court.  Storage can be an issue, especially since a civil case may take years to go to trial.

Bike shops often have a number of the cardboard boxes in which new bikes are delivered. They would gladly share them with law enforcement instead of throwing them out! With little disassembly, it may be possible to secure the crashed bike in the box and store it as evidence. A lawsuit is normally filed within a year or two. The plaintiff’s attorney may wish to take possession of the bicycle and other physical evidence at that time. Your department policy can dictate whether or not to release it for civil action.

Clothing and Equipment
The cyclist’s clothing and equipment may significantly increase conspicuity, or visibility to other road users.  It is suggested the clothing the cyclist was wearing at the time of the crash is collected and photographed. It may be helpful to lay it out as it was being worn to best present it as it was on the street. This usually requires going to the hospital or morgue where the cyclist was taken. Clothing may have been removed at the scene by medical staff or by the impact itself.

Photograph any removed clothing or equipment at the scene and, if possible, bring it with you when you photograph the rest of the clothing. If the cyclist was wearing a helmet, it should be saved as evidence. The helmet may help determine the amount of force and the area of impact.  In some instances it may bear evidence as to whether it struck the vehicle, the road surface or multiple surfaces.

Road Surface
Where a bicyclist rides upon a roadway is often determined by the condition of the roadway and shoulder.  A shoulder that is narrow, or has a crumbling edge or potholed surface, is unsafe for riding. So is one that is littered with debris.  These conditions require a cyclist to ride on the right side of the traffic lane.

When a safe shoulder does exist, the portion of the shoulder that is closest to the roadway has less debris than the side nearest the gutter. To avoid debris, experienced cyclists often ride very near the fog line. Where a roadway has a concrete curb and gutter, it is unsafe to ride in the gutter as gutters collect debris and may also be a grade either higher or lower than the adjacent asphalt.

When assessing whether a cyclist was in a portion of the roadway where he “belonged,” investigators need to be aware of the hazards created by curbs and gutters. Nearly all state statutes have the language that a cyclist must ride as “far right” or “as close to the right side as practicable.” “Practicable” essentially means safe.

Since gutter riding is unsafe, the language does not require bicyclists to ride in the gutter.

On occasion a cyclist may choose to ride in the gutter. Inexperienced cyclists, intimidated by traffic, often move as far right as possible to get out of the way of an approaching vehicle, often a truck or other large behicle. This sets up another potential hazard.

If the cyclist moves too close to the curb, he may actually strike it with the bike’s closest pedal. Doing so can cause the cyclist to launch himself out into the traffic he was trying to avoid. If this is suspected, it may be possible to find evidence of the pedal strike by inspecting both the pedal and the top of the curb.

An recently popular engineering feature are shoulder rumble strips. These are most often installed on higher-speed highways with infrequent bicycle traffic. They are intended to awaken sleepy, distracted or intoxicated drivers to the fact they are leaving the traffic lane.  The rumble strips are unsafe and unrideable for most cyclists, but especially for road cyclists.

Road cyclists ride light bikes that have no suspension, use narrow tires and drop handlebars. Road cyclists avoid rumble strips and will use whatever part of the roadway is available to steer clear of them. If investigating a crash where they are installed, be conscious of their possible involvement. Measure the width of the shoulder and traffic lanes to help determine if there was sufficient space for the cyclist to ride.

The things to take from this series are fairly simple. First, you cannot take too many photos of the bicycle, accessories and damage to the car. Shoot every little detail, both distant and macro. Photograph the clothing worn by the cyclist. Interview witnesses who saw the incident. Examine and measure the roadway and shoulder at least one block prior to the crash scene, if in question.

Review the bicycle statutes in your state. If necessary, call a trained bike patrol officer to the scene to help with the investigation. Preserve the bicycle for later examination. Finally, prepare a detailed report that will make obvious your investigation was thorough and impartial when it is reviewed months and years down the road.

Kirby Beck is retired after 28 years with the Coon Rapids, MN Police. He is a certified IPMBA Police Cyclist Instructor Trainer. He is an expert witness in bicycle crash cases. He may be reached at Kirby@kbeckconsulting.com.

Part I of this article appeared in the May 2006 issue of Law and Order magazine; Part II appeared in the June 2006 issue of Law and Order magazine, http://www.lawandordermag.com. ; They also appeared in the Spring and Summer 2007 issues of IPMBA News.

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    If a bicycle crash results in a death or serious injury, assume that the incident will result in a lawsuit. Many officers don’t seem to know, or care, that they do. Training in bicycle traffic law is virtually non-existent in police academies and crash investigation courses.

    12:14pm, 05/15/2017

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