Documentation:FIB book/Airbag Mechanisms in Motorcycles
Importance of Motorcycle Safety Mechanisms
Background
Motorcycle accidents are a significant public health and safety concern due to the high risk of severe and fatal injuries. Despite advancements in protective gear, including helmets and reinforced clothing, motorcyclists continue to experience disproportionately high rates of life-threatening trauma. Moreover, 50% of all possible motorcycle injuries can be prevented if effective clothing is worn[1].
A comprehensive study analyzing 464 motorcycle accidents in Hanover and Dresden, Germany, between 2010 and 2015 revealed that despite helmet use, 22% of motorcyclists still suffered head injuries, with 3.0% classified as severe (AIS 3+)[2].
While prior data shows that the number of minor injuries among motorcyclists has decreased since 1991, the incidence of severe and fatal injuries has not followed the same downward trend[2]. In comparison to the effort and results of reducing severe and fatal car crash injuries through proper crash testing, safety designs, and regulations, motorcycles have not undergone such improvement, and remain very dangerous. This reinforces the need for additional safety measures beyond traditional protective equipment.
Collision Types & Injury Severity[2]
Motorcycles most frequently collide with cars and fixed objects, with a significantly smaller portion involving trucks. When crashes are categorized by injury severity, truck collisions are the most dangerous, resulting in the highest proportion of severely injured riders (MAIS 3+). This information is visually summarized in Figure(s) 1(a) and 1(b).
Common Injury Regions[2]
These different kinds of motorcycle crashes frequently lead to injuries, with soft tissue damage being the most common, followed by fractures. These injuries are most prevalent in the arms and legs. Thorax injuries are also notable, with some cases leading to lung injuries. While head injuries occur less frequently, they are often more severe, involving concussions, and occasional facial or skull fractures. A detailed statistical breakdown of these and other common injuries is provided in the table below.
n-number | percentage | n-number | percentage | |||
---|---|---|---|---|---|---|
soft tissue injury head | 98 | 3.6% | fx hand/wrist | 87 | 3.2% | |
fx face | 44 | 1.6% | arms (other) | 20 | 0.7% | |
fx skull | 18 | 0.7% | soft tissure injury abdomen | 46 | 1.7% | |
fx skullbase | 10 | 0.4% | lumbar spine | 39 | 1.4% | |
commotio | 69 | 2.5% | liver/gall | 9 | 0.3% | |
cerebral/eye | 40 | 1.5% | spleen | 10 | 0.4% | |
soft tissue injury neck | 17 | 0.6% | stomach | 1 | 0.0% | |
whiplash injury | 60 | 2.2% | intestine | 1 | 0.0% | |
fracture cervical spine | 23 | 0.8% | kidney | 7 | 0.3% | |
neck (other) | 9 | 0.3% | abdomen n.f.s. | 2 | 0.1% | |
soft tissue injury thorax | 183 | 6.7% | soft tissue injury pelvis | 92 | 3.4% | |
fx rips | 76 | 2.8% | fx pelvis | 34 | 1.2% | |
fx sternum | 8 | 0.3% | pelvic organs | 6 | 0.2% | |
fx shoulder | 105 | 3.9% | pelvic vessels | 1 | 0.0% | |
thoracic spine | 53 | 1.9% | soft tissue injury legs | 694 | 25.5% | |
heart | 6 | 0.2% | fx hip | 1 | 0.0% | |
lungs | 52 | 1.9% | fx upper leg | 27 | 1.0% | |
thorax vessels | 10 | 0.4% | fx knee | 11 | 0.4% | |
thorax n.f.s. | 16 | 0.6% | fx lower leg | 68 | 2.5% | |
soft tissue injury arms | 408 | 15.0% | fx feet, ankle joint | 91 | 3.3% | |
fx upper arm | 19 | 0.7% | legs (other) | 24 | 0.9% | |
fx elbow | 5 | 0.2% | other | 15 | 0.6% | |
fx lower arm | 110 | 4.0% | overall | 2725 | 100.0% |
Unlike occupants of other motor vehicles, who benefit from built-in protective features such as seatbelts, airbags, and enclosed frames, motorcyclists are far more exposed and vulnerable in the event of a crash. Considering the high likelihood of MAIS 1 and 2 level injuries—such as soft tissue damage and fractures—along with the notable (~20%) risk of more serious MAIS 3+ injuries like concussions, the importance of safety mechanisms for motorcyclists becomes clear.
Motorcycle Airbag Principle
A potential solution draws inspiration from standard automotive safety features—specifically, airbags—and applies them to motorcycle systems. Companies like Honda have pioneered efforts to reduce the severity of injuries in frontal crashes, with studies showing that motorcycle airbag systems can significantly lower the risk of serious injury in head-on collisions[1][3]. Another major advancement in rider safety is the development of wearable airbag systems. These provide broader protection by responding to a wider range of accident scenarios, including low-side, high-side, and angular collisions[1].
Similar to car airbags, motorcycle airbags focus on the following maxims for restraint performance:
- Maximize the distance over which the restraint forces act
- Distribute forces over a greatest possible area
- Apply restraint forces as soon as possible
Based on current research, airbag mechanisms implemented in the following systems will be explored:
- Touring Bikes (By: Honda, IMMA, YAMAHA)
- Non-touring Motorcycles
- Wearable Airbags
Current Airbag Mechanisms for Touring Bikes
Honda Airbag 1990 Prototype
Since the early 1960s, many motorcycle manufacturers have investigated alternative safety mechanisms to decrease fatality during collisions[3]. Honda, a Japanese automotive manufacturer, pioneered the motorcycle airbag system. In the late-1990s, a prototype airbag system including a sensor system was fabricated and mounted on a Honda GL1500 large touring motorcycle[3][4]. A touring motorcycle was chosen due to its potential for airbag integration given its technical features, such as the fuel tank's location beneath the seat, its large size, and upright riding position. The airbag was designed to deploy from the front of the motorcycle, typically from behind or around the handlebar area. This setup positions the airbag directly in front of the rider, allowing it to effectively intercept and cushion the rider before they make contact with any opposing objects or vehicles during a frontal collision. The initial prototype airbag system was evaluated with six impact configurations, involving 12 full-scale crash tests, 200 impact configurations, and 400 computer simulated crash tests in accordance with ISO13232. Two examples of their six impact configurations were impacted with a stationary car and a moving car.
- Stationary Car Impact: A moving motorcycle at 50 km/h hits the side of a stationary car at a 30° angle, like hitting a car pulling out into traffic.
- Moving Car Impact: A moving car and motorcycle collide at a 30° angle, both in motion. This simulates more complex, real-world crashes where both vehicles contribute to the impact force.
The results from this initial study showed decreased injuries in four test pairs (comparing with and without airbags), increased injury in two test pairs, and little to no injury change in nine test pairs. MATDs (Motorcyclist anthropometric test dummies) measure injuries to head, neck, chest, legs, by looking at peak accelerations[4]. For the computer simulations, LS-DYNA software was used to assess injuries with and without airbags[4]. From this it was decided that more research would be needed to study impacts in which airbags were found to be harmful in order to identify possible solutions. To identify airbag benefits and potential risks, further understanding was needed in other crash and non-crash situations.
Honda Airbag 2006 Version
The 1990s prototype had a few major limitations, including a lack of standardized injury evaluation, especially for neck injuries, delayed airbag deployment, and unreliable crash detection logic. Honda continued to iterate the system, addressing the failures of the previous prototype. This new system featured a larger airbag and more powerful inflator, designed to better manage the dynamics of the dummy during crashes, focused on mitigating movements that led to increased head and neck injuries. The modified airbag system underwent multiple stages of testing including static inflation tests, sled tests, and full scale crash tests[4]. Additionally, it's worth noting that in 2003, the MATD was significantly revised, particularly in the neck structure, to improve biofidelity across a wide range of motorcycle crash scenarios. Thus, the 2006 airbag was tested using a more accurate ATD[5]. Along with physical iterations, the airbag detection system underwent many programming changes to detect crashes with increased accuracy and speed. A faster, fork-mounted sensor system enabled deployment within ~45 milliseconds, ensuring the airbag inflated before the rider made contact. Because this specific system is only meant to deploy during severe frontal-impact crashes, the detection system must be sensitive enough to discriminate between different crash types and general noise felt during normal motorcycle activity. Two pairs of accelerometers were installed on either leg of the front suspension fork leg[3]. These four accelerometers work together to more accurately detect crashes. The values of each fork are averaged to filter noise such as bumpy roads, sharp turns and quick accelerations, hallmarks of motorcyclist activity. This would soon become the airbag system integrated into the 2006 Honda Gold wing, a motorcycle still being sold today. It remains the only production motorcycle with a factory-installed airbag system.
IMMA Airbag Research
Around the same time as Honda's research, several groups, including the International Motorcycle Manufacturers Association (IMMA), began investigating the feasibility of motorcycle airbags[6]. During Phase 1 of the IMMA trials, 19 forward-impact sled tests were conducted, highlighting the significance of neck-airbag interaction. It was found that neck-airbag interaction is a particularly notable factor for riders in a forward-leaning position. Additionally, 750 computer simulations using an 84-liter airbag revealed an increased risk of neck injuries, along with heightened head and chest injuries in certain impact scenarios.
YAMAHA Airbag
As motorcycle airbags began to gain more traction, in partnership with the Ministry of Land, Infrastructure and Transport, Yamaha participated in the Advanced Safety Vehicle (ASV) project[7]. The ASV-2 airbag was developed and tested from 1996-2000. The development of the ASV-2 airbag focuses on making it more applicable to a variety of collision scenarios by prioritizing rider deceleration rather than preventing impact altogether. In the initial testing process, sled tests and full scale motorcycle frontal collisions into a stationary barrier confirmed its preliminary effectiveness. In order to investigate a wide variety of collision scenarios further, two computer simulation models were used. The first was MADYMO, a multi-body dynamic analysis software that models rigid bodies, joints, and surfaces to approximate object shapes[7]. The second was PAM-SAFE, a finite element-based collision analysis software that improves MADYMO’s accuracy. MADYMO uses a simplified airbag model that does not accurately capture the initial deployment phase or gas flow, leading to inaccuracies in airbag geometry. PAM-SAFE addresses these limitations by accounting for nonlinear deformations of the front tires and forks during collisions. For simple yet precise simulation of motorcycle crashworthiness and to test airbag systems, MADYMO was used as the base simulation method, with parts of PAM-SAFE results integrated into the MADYMO model for higher computational accuracy[7]. The airbag system itself consists of three separate chambers and a backplate stored within the motorcycle body. During deployment, the center chamber inflates first, pulling the backplate into position. Gas then flows into the left and right chambers through holes in the dividers, allowing them to fully inflate. The backplate plays a crucial role by absorbing the majority of the airbag’s force and ensuring proper inflation, particularly for oblique impacts. By keeping the airbag as close to the rider as possible, in conjunction with the backplate’s support, the system enhances overall protection and effectiveness in various crash configurations. Despite extensive testing, this airbag system was never implemented in any motorcycles due to its high variability in various testing scenarios.
Airbags for Non-Touring Motorcycles
Generally, an airbag system requires supporting structures to receive the reaction force in order to position the airbag during a crash and absorb the kinetic energy of the occupant or rider. Previously developed systems employed a configuration in which the airbag was supported by the structures of a touring motorcycle, such as the instrument panel and the surrounding structures[8]. However, Aikyo et al. discuss how sufficient reaction structures are not present in all motorcycle models, specifically those not equipped with an instrument panel and surrounding structures large enough to receive the reaction force. Therefore, this study proposes an airbag design that is applicable to motorcycles that do not have a sufficient reaction structure. The concept behind this airbag system is that, during a collision, the structures of the opposing vehicle will serve as the reaction structures, rather than relying on the motorcycle's own frame.
In terms of testing, this study involved full-scale motorcycle-to-car crash tests using 125 cm³ scooter-type models, with and without the new airbag system. These tests were conducted in accordance with the seven impact configurations specified by ISO13232, focusing on the airbag’s effectiveness in different collision scenarios[8]. Figure 5 shows the different configurations.
For this design, the airbag is divided into three primary sections, each designed to fulfill a specific function during a collision:
- Top Section (Area A): This part is designed to contact the upper structures of an opposing vehicle, such as the roof or higher body panels. Its main function is to support the airbag during deployment by using the opposing vehicle as a reaction structure
- Middle Section (Area B): This is the thickest part of the airbag and serves as the primary protective barrier for the rider’s head. It is crucial for absorbing the kinetic energy resulting from the rider's forward motion during a crash, reducing the impact forces transmitted to the rider.
- Bottom Section (Area C): This section helps to stabilize and maintain the positioning of the airbag relative to both the motorcycle and the rider. It ensures that the middle section remains properly aligned to maximize protection during the impact.
The results from the various crash tests confirmed the protective benefits of the airbag system in specific impact configurations, showing a reduction in rider injuries. Importantly, no significant risks or adverse effects were associated with the airbag during the tests. The results supported the feasibility of using the opposing vehicle’s structures as reaction structures, particularly in collisions where the motorcycle itself lacks sufficient built-in support for an airbag[8].
Wearable Airbags
Wearable airbags are an alternative safety device to built-in airbag systems. Similar to regular airbags, these wearables inflate during frontal and oblique crashes to protect the rider against serious injuries to the chest, abdomen, and back[1].
Based on current research, there are two main ways wearable airbags can be deployed:
Mechanical Method
The "Mechanical Method" uses a cable or tether that connects the rider to the motorcycle. In the event of a collision or fall, the cable is physically disconnected. This action triggers the airbag deployment: as the rider separates from the motorbike, a coil wire pulls a key from the gas release mechanism, releasing gas to inflate the wearable vest[9]. This method is considered more reliable than the "Sensor Method" discussed below; however, it requires the rider to ‘fall’ enough to trigger the mechanism, and does not guarantee safety during roll out or slippage[1][9].
Sensor Method
Building upon research established in the "Mechanical Method", a 2021 research initiative was taken to design an “Automatic Air Inflated Tubeless Safety Jacket”[9]. The design has a deployment mechanism within the jacket itself, unlike existing tethered or mounted systems. Utilizing sensor data, a shorter reaction time for inflation is achieved, as well as more protection for “roll out” crashes compared to the "Mechanical Method" designs.
The jacket's crash testing mechanism includes two key tested scenarios: collisions with barriers, and falling due to slippage or imbalance while riding. In both cases, the system's sensors detect the accident, sending a signal to the Electronic Control Unit (ECU) that triggers a chemical reaction to produce nitrogen gas. This gas then inflates the jacket, providing immediate protection.
The design faced challenges such as balancing comfort, aesthetics, and technical performance. The need for cost-effectiveness also led to some sacrifices in features like UV and flame resistance[9].
Effectiveness of Wearable Airbags[10]
In 2019, a study was performed by Serre et al. with the goal of evaluating the effectiveness of wearable airbags. This study used a double approach to combine real accident data and experimental lab data. The real accident data was collected from a survey in France concerning motorcyclists equipped with wearable airbags. Data such as motorcycle damage, airbag damage, crash configuration, and injuries were used to create a kinematic reconstruction with MADYMO to determine the impact speeds experienced.
The experimental testing involved the use of four PMHS with wearable airbags (2 cable triggered/"Mechanical Method", 2 sensor triggered/"Sensor Method") impacting a vehicle’s B-pillar at 40 km/h. Each PMHS was instrumented with five three-axis accelerometers which can be seen in Figure 7. Airbag inflation time, airbag pressure, PMHS accelerations, and injuries on the PMHS were collected.
The study determined that the level of protection provided by the device is strongly dependent on impact speed and impact configuration. Generally, these airbags can protect against severe injuries at speeds of 30-40 km/h. However, in direct impacts above 40 km/h and falls at 60 km/h, the device was unable to prevent serious trunk injuries (AIS3+). It is also worth noting that motorcyclists stated that they felt better protected while equipped with a wearable airbag.
Problems & Controversies
Motorcycle Airbags
Motorcycle airbag development presents several challenges. Unlike airbag systems in cars, motorcycle airbags must account for environmental exposure, greater variability in rider positioning, and the risk of improper deployment[4][8]. Some studies have shown that airbag deployment in certain crash scenarios can alter a driver's trajectory in ways that may increase risk of injury[4][5]. Additionally, there are concerns over how airbags interact with riders' necks in forward-leaning riding positions[5].
The main challenges in developing motorcycle airbags include the variability in rider size, helmet-airbag interaction, crash dynamics, and environmental exposure. Firstly, unlike cars, which have ample dashboard space to install airbags, many motorcycle models physically do not have the space to add an airbag system. Moreover, traditional airbags in vehicles rely on the vehicle structure as a reaction structure for deployment[8]. Consequently, the wide range of variables involved in motorcycle crashes- including crash direction, crash speed, rider positioning, motorcycle size, and frame rigidity- limits the universal effectiveness of airbags, particularly in non-frontal collisions or in motorcycles with less rigid frames[8]. There is also limited research on the effects of airbag systems on tandem motorcycle riders[7]. Additionally, the variability in motorcycle shape and size makes it difficult to create a universally effective airbag system[4]. Notably, many riders also do not want the extra weight of added airbags to their motorcycles. Motorcycle helmets are also an additional variable to be considered, as most helmet to airbag interactions are extremely specific to the type of helmet being worn. Finally, unlike car airbag systems, which are housed within the vehicle’s interior, motorcycle airbag systems are exposed to the elements with only a single layer of plastic protecting the bag. As a result, they must endure rain, extreme temperatures, and continuous wear while maintaining reliability and performance[5]. Thus, these concerns have limited built-in motorcycle airbag development.
Wearable Airbags
Wearable airbags face issues dependent on deployment methods. "Mechanical Method" systems fail to guarantee rider safety during roll out or slippage, due to its reliance on the rider ‘falling’ enough to trigger deployment[9]. Moreover, the "Sensor Method" design of the “Automatic Air Inflated Tubeless Safety Jacket” faced challenges such as balancing comfort, aesthetics, and technical performance. The need for cost-effectiveness also led to some sacrifices in features such as UV and flame resistance[9]. Delays in reaction time is also a concern around current wearable airbag systems.
Crash Testing & Simulations
Studies have undergone motorcycle crash testing with airbags using the Hybrid III as an ATD[6]. However, the Hybrid III neck only moves sagittally. The human neck experiences movement in the 3D plane, rendering the ATD used non-biofidelic in this context. Biofidelic neck movement in airbag crash tests are especially relevant given the concerns over airbag-neck interaction as outlined above. Additionally, the airbag simulation model[7] was simplified and did not include gas flow, resulting in inaccurate deployment geometry.
Future Work
Researchers have identified advancements to motorcycle airbags and rider-specific safety enhancements as avenues to improve motorcycle safety[9]. Further crash testing with biofidelic ATDs, specifically 3D neck movement, could lead to design changes and advancements that quell safety concerns surrounding airbags in motorcycles. In the case of wearables, developing airbags with quicker reaction times could improve rider safety. The development of motorcycle airbag simulation models with current computational technology could prove to be more effective than the software used in past models[7]. Lastly, further consumer research and adoption studies on airbag systems in motorcycles would serve to help identify factors that would influence the implementation of airbags amongst motorcyclists widely.
Copyright Statement
All content in this WikiPage complies with copyright regulations. All content was either created by student contributors, used under an appropriate Creative Commons (CC) license with proper attribution, or embedded or linked from original sources without modification. No copyrighted materials have been reproduced without permission.
References
- ↑ Jump up to: 1.0 1.1 1.2 1.3 1.4 E. Marconi, F. Gatto, and M. Massaro, “Numerical and Experimental Assessment of the Performance of Wearable Airbags for Motorcycle Riders,” in Proc. World Congr. on Eng. Jul. 2018. [Online]. Available: https://www.researchgate.net/publication/326439988_Numerical_and_Experimental_Assessment_of_the_Performance_of_Wearable_Airbags_for_Motorcycle_Riders
- ↑ Jump up to: 2.0 2.1 2.2 2.3 2.4 D. Otte, “Residual Injury Situation and Accident Characteristics of Severe Motorcycle Accidents,” SAE Tech. Paper, Apr. 2019, doi: 10.4271/2019-01-0638.
- ↑ Jump up to: 3.0 3.1 3.2 3.3 Y. Kobayashi and T. Makabe, “Crash Detection Method for Motorcycle Airbag System with Sensors on the Front Fork,” in 23rd Int. Tech. Conf. on the ESV, Jun. 2013. [Online]. Available: https://www-nrd.nhtsa.dot.gov/departments/esv/23rd/files/23ESV-000113.PDF
- ↑ Jump up to: 4.0 4.1 4.2 4.3 4.4 4.5 4.6 T. Kuroe, H. Namiki, and S. Iijima, “Exploratory Study of an Airbag Concept for a Large Touring Motorcycle: Further Research Second Report,” Honda R&D, Jan. 1, 2005. [Online]. Available: https://www.researchgate.net/publication/242159424_EXPLORATORY_STUDY_OF_AN_AIRBAG_CONCEPT_FOR_A_LARGE_TOURING_MOTORCYCLE_FURTHER_RESEARCH_SECOND_REPORT
- ↑ Jump up to: 5.0 5.1 5.2 5.3 C. Withnall, N. Shewchenko, K. D. Wiley, and N. Rogers, "An Improved Dummy Neck for the ISO 13232 Motorcycle Antropometric Test Dummy," in Proc. of 18th Int. Tech. Conf. on the ESV, 2003. [Online]. Available: https://biokinetics.com/wp-content/uploads/2024/04/WIthnall-et-al-2003-An-Improved-Dummy-for-ISO-13232-MATD-ESV.pdf
- ↑ Jump up to: 6.0 6.1 N. M. Rogers and J. W. Zellner, “Factors and status of motorcycle airbag feasibility research,” in Int. Tech. Conf. on ESV, Jun. 2001. [Online]. Available: https://www.sae.org/publications/technical-papers/content/2001-06-0102/
- ↑ Jump up to: 7.0 7.1 7.2 7.3 7.4 7.5 M. Deguchi, S. Kanbe, and Y. Hannya, “Basic Research for Motorcycle Crashworthiness and a New Airbag System,” SAE Tech. Paper, Oct. 2007, doi: 10.4271/2007-32-0106.
- ↑ Jump up to: 8.0 8.1 8.2 8.3 8.4 8.5 Y. Aikyo, Y. Kobayashi, T. Sato, T. Akashi, and M. Ishiwatari, “Study on Airbag Concept for Motorcycles Using Opposing Vehicle as Reaction Structure,” SAE Int. J. of Engines, vol. 9, no. 1, pp. 473–482, Nov. 2015, doi: 10.4271/2015-32-0813.
- ↑ Jump up to: 9.0 9.1 9.2 9.3 9.4 9.5 9.6 R. L. Bulathsinghala, S. Fernando, T. S. Jayawardana, N. Heenkenda, and D. Wijesena, "An automatic air inflated tubeless safety jacket for motorbike riders,” Res. J. of Textile and Apparel., Jun. 2021, doi: 10.1108/RJTA-01-2021-0002.
- ↑ T. Serre, C. Masson, M. Llari, B. Canu., M. Py, and C. Perrin, “Airbag Jacket for Motorcyclists: Evaluation of Real Effectiveness,” in IRCOBI Conf., 2019, pp. 533-537. [Online]. Available: https://www.ircobi.org/wordpress/downloads/irc19/pdf-files/76.pdf