National Agenda for Motorcycle Safety | Motorcycle Factors

  • P0024709Motorcycle Design
  • Braking
  • Vehicle Modifications
  • Conspicuity
  • Lane Use
  • Glossary

Motorcycle Design

The design of motorcycles has made them increasingly more capable and specialized, and generally reflects a greater emphasis on safety.

In general, motorcycle design has yielded steady safety improvements. The motorcycles of today are better in virtually every significant safety area than those of just two decades ago.

Current motorcycles have better brakes, greater stability, more responsive steering, more effective controls, improved ergonomics for better control and reduced fatigue, and improved reliability in all systems than those of even a decade ago.

The acceleration and top speed of the most powerful models (mostly sportbikes) have increased continually. The effect of these performance increases on safety is currently unknown.

Tires, which are particularly crucial components on a two-wheeled vehicle, have advanced significantly and have contributed much to vehicle performance, reliability, and safety. Modern tires are more durable, offer better traction for turning and stopping, and have contributed to significantly improving stability compared with their counterparts of the 1970s.

Some motorcycles have hand and foot controls that can be adjusted to accommodate various riders with larger or smaller than average hands and feet, thereby increasing the riders’ control of these motorcycles.

Brakes are often significantly more powerful and can have an antilock braking system and/or linked front and rear application.

Lack of rider protection is a characteristic of all motorcycles. Research into devices to reduce rider injuries in crashes is ongoing. Because of the lack of coupling between motorcycle and rider (which would create an additional hazard), motorcycle-mounted rider protection systems have significant limitations

  • Leg protectors have been devised and studied in the United States and internationally, but the results have been mixed thus far. There is no widespread agreement that they provide additional protection, and they may pose safety drawbacks.
  • Motorcycle airbags have been under study for 30 years both as vehicle equipment and as a part of the rider’s apparel. At this time, the benefits and risks, such as undesired deployment, are still under investigation

The evolution and specialization of street motorcycles to meet specific requirements of the market have created some design features that raise safety issues and suggest further research.

  • Studies of earlier types of machines have shown that fuel tanks that rise abruptly from the saddle immediately in front of the rider contribute to severe pelvic injuries in frontal impacts. Most current sportbike tanks have a similar style and are likely to present a similar injury mechanism.
  • Some cruiser and touring motorcycles place components, such as instruments and controls, atop the fuel tank. These designs may increase uro-genital injuries during crashes.
  • Motorcyclists complain that windshields that extend through a rider’s line of sight impede vision under certain conditions, including rain and nighttime.
  • Although tubeless tires significantly reduce the likelihood of a blowout and resulting loss of control, tube-type tires are still fitted to many cruiser models in order to use wire-spoke wheels for appearance reasons. However, alter-native wire-spoke wheel designs exist that may be used with tubeless tires. Wire wheels may also be sealed for use with tubeless tires. The Hurt Report listed puncture flats as the primary motorcycle vehicle failure leading to crashes.
  • Emphasis on styling simplicity, the search for weight reduction, and lack of space often dictates a single-bulb taillight. The failure of either the taillight or brake-light filament can leave the motorcyclist without rear lighting.

To understand the effects of current motorcycle design on safety. Specific issues that must be addressed include:

  • The effects of rapid acceleration and high top speeds
  • The run-flat performance of motorcycle tires
  • Injury mechanisms of current designs

As with other vehicles, fashion is a significant factor in motorcycle design. However, there may be some safety consequences that are not desirable. Safety should not be sacrificed for the sake of fashion.

More motorcycles should offer control adjustments to accommodate riders who are larger or smaller than average.

Research is needed to learn about the effects of current motorcycle design and performance on safety.

Although some issues raised here concerning motorcycle design await research and technology for solutions, others—such as vision restrictions and tube-type tires—can be addressed with current technology as research results dictate.

  • U.S. Department of Transportation Recommendations
    • Conduct research to determine how current motorcycle designs affect crash and injury causation.
    • Implement the use of available tire and wheel technology and explore technology, such as run-flat tires, to reduce frequency of loss-of-control crashes caused by puncture flats.

 

Braking

Although motorcycles have sufficient braking power and traction to enable them to stop in as short a distance as a typical car, panic-braking a motorcycle poses unique hazards and requires greater operator skill than stopping a car in panic situations or in a skid.

The vast majority of motorcycles use an independent system for the front and rear wheels, with a lever on the right handlebar controlling the front brake and foot pedal controlling the rear brake. A small number of motorcycles link the controls and an even smaller number have a handlebar lever to control the rear brake. We know of no current research that indicates which if any of these is more effective.

Braking seems to be one of the most difficult skills for a motorcyclist to master. It is also one of the most critical. It is difficult because most motorcycles have two separate brake-control systems, one for the front wheel and one for the rear wheel. As the front brake is applied, weight transfers to the front tire, which causes available traction to vary as weight shifts, requiring the rider to adjust pressure on each brake control in a maximum-performance stop. As found in the Hurt Report, in a situation the motorcyclist typically overbrakes the rear and underbrakes the front, even though weight transfer means the front brake must do the majority of the braking. Overbraking can either cause loss of steering control or total loss of control. If the rear wheel is locked, the rider typically loses directional control. If the front wheel locks, the rider is likely to crash due to loss of stability.

Rider training courses, available for the last two decades, have sought to develop improved motorcyclist braking skills. Greater emphasis has been focused on proper braking technique and the importance of the front brake. There seems to be a greater recognition of the importance of front brake use than there was 20 years ago when the Hurt Report was conducted. Failure to brake effectively and loss of control during panic-braking continue to play a role in motorcycle crashes.

Continued rider training and practice are key elements in assuring maximum rider performance in a panic situation. This allows riders to learn brake control during a maximum-braking stop, internalize the process of a hard stop so they react automatically in a panic situation, and deal with events such as rear-wheel lock-up. However, even panic-braking practice involves risk, because locking the front wheel can cause an immediate loss of control and a fall. This makes it difficult for rider training organizations to train riders to use the front brake to its full capability.

Motorcycle braking systems have steadily improved in terms of power, control, and reliability and continue to do so. Virtually all street motorcycles now have hydraulically actuated disc brakes, at least on the front wheel. Most motorcycles use this type of brake—which is self-adjusting for wear and more resistant to fade and wet conditions than drum-type brakes—on the rear wheel as well.

Many street motorcycles also have powerful dual disc brakes on the front wheel, which provide more stopping power where it is needed most. This is particularly true for sportbikes and touring motorcycles. Cruisers, despite weights that are normally heavier than other styles except touring motorcycles, often have just a single disc brake in front, although this seems to be changing.

Two technical developments have sought to simplify braking control and provide more effective braking. Linked braking slows both wheels with a single control. Antilock braking systems (ABS) allow the rider to apply maximum braking force without fear of wheel lock-up and the resulting loss of control, providing the bike is not leaned over. Under many pavement conditions, antilock brake systems allow the rider to stop a motorcycle more rapidly while maintaining steering control even during situations of extreme, panic braking.

Although incidental and first-hand experience indicates either of these systems can be effective in countering the problems faced by a motor-cyclist in a panic stop, we know of no research that shows how they perform in the field compared with similar bikes fitted with standard brake systems. The added costs (particularly for ABS) and reluctance to accept them by some experienced motorcyclists have limited the adoption of these potentially effective systems.

Motorcyclists to possess the skills to use their brakes fully while maintaining control under all riding conditions, thus avoiding some crashes.

We would like developments in brake systems, which offer better, safer panic-stopping capability for motorcyclists, to continue and be more widely adapted to all classes of motorcycles.

Assuring that motorcyclists get maximum braking performance requires training, research, and deployment of equipment that can provide maximum-performance braking while minimizing the danger of a braking-induced crash. To obtain the level of braking that is available even on current machines, both experienced and inexperienced motorcyclists need recurrent training

Several braking issues invite further study:

  • The new technologies seem to promise shorter stopping distances and overall safer stopping for motorcyclists. ABS in particular can do much to eliminate the dangers of overbraking in a straight line.
  • Studies of how effectively linked-braking systems perform in the field would tell whether they should be employed more widely.
  • The effectiveness of braking systems that combine ABS with a linked control should be explored.
  • U.S. Department of Transportation Recommendations
    • Study the effectiveness of linked and antilock braking in the field. If these technologies prove valuable, deploy them more widely.
    • Use information from research to implement other braking-related countermeasures.
    • Provide additional training and education on proper braking and panic-braking techniques.

 

Vehicle Modifications

A motorcycle’s relatively simple design and availability of replacement or accessory components make it easy, inexpensive and popular to modify with unknown safety consequences.

Virtually every part of a motorcycle can be modified, and many modifications can affect the safety of the vehicle. Modifications aimed at improving or changing the way the machine works include those directed at engine performance, comfort, handling, braking, or cargo capacity. Some changes are made to personalize and customize the appearance. Even seemingly simple, routine changes—such as fitting new tires—can change a motorcycle’s handling.

Some changes (such as upgrading suspension components, tires, or brake components) can be purely beneficial, while others can be mostly detrimental from a functional standpoint. Many involve trade-offs. For example, a motorcycle that is lowered to give the rider a more surefooted stance at a stop gives up some cornering ground clearance and suspension travel. Some changes, such as major frame modifications or use of an aftermarket frame, can change the entire character of the motorcycle. Installation of a sidecar or a three-wheeled “trike” kit creates an entirely different class of vehicle that no longer handles or responds like a two-wheeled motorcycle.

Although trailers towed behind motorcycles have become more popular, we know of no data that indicate their effect on motorcycle behavior. Most motorcycle manufacturers warn against their use, however.

Users may install aftermarket components or make modifications that their motorcycles were not designed for or tested with. They may combine modifications that were not designed to be together and when combined have unforeseen effects on the performance of the vehicle. Riders may also fail to understand all the consequences of a change. Some changes also lend themselves to misuse. Adding a cargo compartment or a luggage rack at the rear of the motorcycle, for example, may allow the user to place too much weight there despite labels warning against it. A change in weight distribution can significantly alter how a motorcycle handles.

The Hurt Report showed that modified vehicles were over-represented in crashes. However, the types of vehicles created by the modifi-cations specified in that study—known then as semi-choppers—now constitute the two largest subcategories of original equipment street motorcycle: sportbikes and cruisers.

Because a motorcycle created by an aftermarket or user-created modification is much different than one built by a manufacturer, the current situation has changed too much for that aspect of the study to be relevant. The Hurt Report also found street motorcycles with modified exhaust systems were over-represented in crashes.

As with original equipment, the quality and safety of most aftermarket components have steadily improved, although seemingly they haven’t reached the levels of original equipment components yet. Users have access to more information of such products from manufacturers than in the past, and the user is likely to be better informed of the possible drawbacks to the modification. The liability climate has also made suppliers and installers more cautious about modifying motorcycles.

Some of the most questionable modifications that were popular during the era the Hurt Report was conducted, such as removing the front brake, have fallen out of style. It is not clear, therefore, if modifications are still a significant factor in motorcycle crashes.

The modifications favored by motorcyclists change with technology, fashion, and other factors, which makes most specific regulations unfeasible. Some countries, such as Germany, require that prior to any sale of a motorcycle, any of its modifications must be tested and certified. Although this may prevent some crashes, it may also cause some by limiting the riders’ access to superior tires, brakes, suspension, and other components.

The current role of vehicle modifications in motorcycle crashes should be better understood.

All aftermarket vendors should make safety a priority in the development of motorcycle accessories.

Any future studies of crash causation should certainly examine the role of modifications to motorcycles, particularly major changes such as chassis modifications, sidecars, and trailers. Since some alterations may be under-represented in motorcycle crashes, that issue should also be addressed. Education of riders may be a better approach to dealing with modification-related problems than regulations.

  • U.S. Department of Transportation Recommendations
    • Study the role of modifications in current motorcycle crashes.
    • Educate users about how modifications and loads can change the operating characteristics of their motorcycles.

 

Conspicuity

Motorcyclists who are conspicuous are under-represented in crashes.

A common complaint of street riders is that other motorists fail to observe them. Motorists who violate motorcyclists’ right-of-way frequently state, “I didn’t see him,” or “He came out of nowhere”.

The problem of other motorists failing to observe motorcyclists apparently exists on several levels. An important Hurt Report finding was that conspicuous motorcycles and riders were less likely to have their right-of-way violated by other vehicles.

A variety of recognized tactics exists to make motorcycles and their riders more conspicuous: lighting, surface color and size, and rider traffic strategy.

Lighting factors include:

  • Since 1979, most motorcycles sold in the United States have been equipped with automatic-on headlamps to meet some state requirements. This seems to have been an effective method of making them more conspicuous and reducing right-of-way violations. Currently, 86 percent of motorcycles on the road have their headlights on during daytime.
  • Using the high beam of a motorcycle’s headlight during the day also helps to prevent violations of the motorcyclist’s right-of-way ).
  • In the cruising and touring categories, auxiliary headlights, usually of reduced wattage, are gaining popularity. Many sportbikes are equipped with dual headlights.
  • Recently, some automobiles have started using daytime running lamps (DRL), which may reduce the effectiveness of motorcycle automatic-on headlamps.
  • Headlight modulators, which cause the light to alternate between a higher and a lower intensity during the day, also increase conspicuity. Headlight modulators are federally regulated lighting devices and as such, all state laws governing them are preempted. Motorcycle headlight modulators have not been studied to determine their effects on other motorists.
  • Many modern street bikes are equipped with position lamps in their front turn signals. This may help other motorists to identify the vehicle as a motorcycle and to better judge its distance and speed.
  • Few motorcycles have more than single-point rear lighting, though multiple lights at the rear would seem to offer similar benefits and also provide redundancy for the single taillight.

The color of and equipment on a motorcycle can play a significant conspicuity role.

  • Motorcycles equipped with additional frontal bodywork (fairings which protect the rider from wind and weather) were found to be under-represented in crashes where motorists violated the motorcyclist’s right-of-way. The larger the fairing and the brighter the color, the more effective it seemed to be in preventing other vehicles’ right-of-way violations
  • During the period of study for the Hurt Report, most fairings were aftermarket accessories added to motorcycles for touring comfort. By the late 1980s, most manufacturers offered some motorcycles with fairings as original equipment. In addition, most sportbikes have smaller, more aerodynamic fairings, that tend to be more brightly colored and often have elaborate graphic designs. Whether the newer sport-style fairings have a significant effect on conspicuity is not known.
  • One of the easiest and most effective ways for a motorcyclist to be seen by other motorists is by wearing brightly colored, upper-torso cloth-ing and/or retro-reflective material. However, only a minority of motorcyclists choose such brightly colored apparel, whether for fashion or other reasons.
  • Social and fashion pressures are apparently a powerful reason for not wearing brightly colored clothing. Although sportbike riders, who imitate racers, have largely accepted bright colors, the larger cruiser category chooses apparel in almost nothing but inconspicuous black. Other categories often choose other hard-to-see colors such as gray, beige, and other neutral colors. The olive-drab and camouflage apparel that the Hurt Report found over-represented in the typical right-of-way-violation crash is still worn.
  • Manufacturers and distributors of helmets confirm that more than half of the motorcycle helmets sold for street use in the United States are black, which seems to be chosen primarily for fashion.

Rider traffic strategy strongly affects visibility

Motorcyclists to be aware of how conspicuity issues affect their safety and prepare accordingly.

We would like states to reconsider regulations that prohibit proven and safe conspicuity-enhancing modifications to lighting systems.

Education of motorcyclists to overcome their resistance to employing conspicuity strategies is needed. Protective apparel manufacturers can help by promoting conspicuity in their advertising and in their apparel designs. Efforts that focus on peer acceptance of conspicuous colors are also suggested.

Research is needed into the matters of conspicuity and why motorcyclists are overlooked by other motorists. Programs should be implemented based on the findings to correct this.

  • Research that explores the reasons why drivers fail to observe motorcyclists despite attempts to be more visible should be a high priority.
  • Information about specific high-conspicuity colors and the uniqueness of applying them to specific locations on the bike or rider would be useful to riders seeking greater conspicuity.
  • DRL usage on cars may influences the environment and effectiveness of motorcycle automatic-on headlamps and warrants investigation.
  • Motorcycle lighting should be studied to find safe ways to increase conspicuity and enhance recognition during the day and at night.
  • U.S. Department of Transportation Recommendations
    • Conduct research to determine why other motorists fail to see and identify motorcyclists and implement countermeasures.
    • Encourage motorcyclists to enhance their conspicuity.
    • Encourage manufacturers to make motorcycle apparel and parts conspicuous.
    • • Reconsider state requirements that prohibit safe conspicuity-enhancing modifications, including safe modification to lighting systems.
    • Conduct research on the effect of automobile DRL on motorcycle safety.

 

Lane Use

Motorcyclists, who have significant room to maneuver while riding within a traffic lane, can use this margin to position themselves for maximum visibility to other motorists while maintaining safety and control of the traffic situation.
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The relatively narrow width of a motorcycle on the road allows its rider to employ many strategies not available to drivers of other vehicles.

  • Motorcyclists can choose their position within their lane to avoid road surface hazards, other vehicles, pedestrians or other mobile hazards, intrusions, or potential intrusions into their right-of-way.
  • Motorcyclists may seek positions where they are in view of other drivers and pedestrians.
  • Motorcyclists may select a position that maximizes their view of the road and traffic ahead.

All states permit motorcycles to use high occupancy vehicle (HOV) lanes with a single rider on the motorcycle. Limited studies evaluating this practice have shown no traffic or safety problems.

A motorcycle’s narrow width can allow it to pass between lanes of stopped or slow-moving cars on roadways where the lanes are wide enough to offer an adequate gap. This option can provide an escape route for motorcyclists who would otherwise be trapped or struck from behind. There is evidence that traveling between lanes of stopped or slow-moving cars (i.e., lane splitting) on multiple-lane roads (such as interstate highways) slightly reduces crash frequency compared with staying within the lane and moving with other traffic.

Although lane splitting is allowed in just a few areas of the United States, notably California, it appears to be worthy of further study because it offers a means of reducing congestion in addition to possible safety benefits. It is widely used in many other countries.

All motorcyclists should be aware of the value of lane positioning to maximize their visibility to other motorists and better manage traffic situations.

We would like to have additional research to provide information about the safety or dangers of lane splitting.

A well conceived lane-position strategy can greatly increase the safety of a motorcyclist, particularly in traffic. More motorcyclists and other motorists need to be apprised of such strategies through rider training and safety messages in the media and methods such as registration renewal flyers.

More research is needed to verify the benefits or hazards of lane splitting.

  • U.S. Department of Transportation Recommendations
    • Study the safety implications of lane splitting.
    • Educate motorcyclists about lane-use strategies, including HOV lane usage.

 

Glossary

Antilock braking system (ABS): A braking system that prevents wheels from locking during braking.

Armor: Padding, hard-shelled material or other impact-absorbing material fitted to a motorcyclist’s apparel. Performance standards exist in Europe for such materials.

Asphalt sealer: Material used to fill and repair cracks in asphalt paving. Materials currently used often create a slick surface that can cause a motorcycle to lose traction.

Automatic-on headlamp: A motorcycle headlamp that is automatically illuminated when the engine is started—also known as daytime running lamp. Required by regulation in many states since 1973 and consequently installed on virtually all street bikes sold in the U.S.

Brake: To stop or slow a motorcycle using the brakes. See also Panic-brake.

Café-racer: Customized motorcycle built in the style currently categorized as a sportbike; popular in the 1970s and early 1980s.

Corner (or cornering): To negotiate a turn in the road. A motorcycle must lean to do so.

Daytime running lamps (DRL): Frontal lighting used to enhance daytime conspicuity of motor vehicles including motorcycles.

DOT: U.S. Department of Transportation

Fairing: Frontal bodywork on a motorcycle intended to make the vehicle more aerodynamic and/or reduce wind pressure on the rider.

FMVSS 218: U.S. Department of Transportation Federal Motor Vehicle Safety Standard No. 218 Motorcycle Helmets.

FMVSS 218 compliant helmet: A motorcycle helmet that complies with U.S. Department of Transportation Federal Motor Vehicle Safety Standard No. 218 (FMVSS 218) for motorcycle helmets.

Front suspension: Often called the “fork” or “forks” because most motorcycles use designs with two parallel legs.

Hurt Report: A study of 900 motorcycle crashes titled Motorcycle Accident Cause Factors and Identification of Countermeasures, authored by H.H. Hurt et al., in 1981. Conducted in the late 1970s, it is considered the most comprehensive study of motorcycle crash causation to date.

Lane splitting: Passing between lanes of stopped or slower-moving vehicles on a motorcycle. Not permitted in most of the U.S., it is allowed in many other countries and may provide a safety benefit. Also called “lane sharing.”

Linked braking: Motorcycle braking systems that use a single control to operate both front and rear brakes.

Manual on Uniform Traffic Control Devices (MUTCD): Contains all national design, application, and placement standards for traffic control devices, including signs, signals, and pavement markings. The MUTCD is published by the Federal Highway Administration (FHWA) under 23 Code of Federal Regulations (CFR), Part 655, Subpart F.

Motorcycle safety: Reducing motorcycling crashes, injuries and fatalities through risk management and countermeasures.

Overbrake: Applying too much force to a brake during a stop, which causes a wheel to stop turning. This can result in loss of directional control (particularly if the rear wheel stops rolling) or upset the motorcycle and cause a crash (a common result of overbraking the front wheel).

Panic-brake: An emergency stop, requiring hard, effective controlled brake application, so called because it is often conducted during a moment of panic.

Position lamps: Additional filaments in a motorcycle’s front turn-signal assemblies that act as full-time running lights to increase conspicuity, distance perception by other drivers, and awareness.

Risk management: The practice of planning for and reducing risk.

Semi-chopper: A motorcycle customized in the style currently categorized as cruiser. In the 1970s, such machines frequently included lengthened front suspension.

Swerve (or swerving): To rapidly change direction, normally employed to avoid an obstacle.

Tiered licensing: A licensing system that provides for operating restrictions based upon motorcycle engine displacement.

Tubeless tire: A tire that retains air without an inner tube. An inner tube (used on a tube-type tire) is necessary to retain air pressure when the wheel design or the tire cannot do so. However, an inner tube typically deflates rapidly when punctured, and this sudden deflation can cause a quick reduction of control on a motorcycle. A tubeless tire typically deflates much more slowly, providing a motorcyclist with warning before control is reduced significantly. Whether a tube-type or tubeless tire is chosen normally depends on the kind of wheel to which it is fitted.

Tube-type tire: See Tubeless tire.

Underbrake: Failure to apply the brakes to their full capability, resulting in a longer than needed stopping distance. This is usually caused by fear of the results of overbraking.

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