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Bicycle helmets offer good protection in impact test

Nov 2020

Vehicle Technology

The potential benefits of bicycle helmets in protecting a cyclist’s head in case of an accident are indisputable. At the same time, figures for helmet usage around the globe are extremely varied, as illustrated strikingly by the data collected from different European countries in the DEKRA Accident Research study presented in the section of this report on the human factor.

DEKRA conducted special impact tests with a variety of helmets.
DEKRA conducted special impact tests with a variety of helmets.

The reasons why a cyclist chooses to wear a helmet – or not – vary, and are influenced by many different factors. The fear of ruining one’s hair or appearance carries just as much weight as factors such as personal experience, the numbers of cyclists on the roads in the area, the type of bicycle, the purpose of the journey and, last but not least, the legal requirements.

Generally speaking, there is a wide variety of helmet models and designs available on the market. The number of products available is as large as the price range. The fundamental requirements are defined in a number of standards, such as EN 1078, CPSC, JIS T 8134, and CAN/CSA-D113.2-M89 (R2014). These standards must be complied with in their respective regions. Providing they meet these basic requirements, however, manufacturers have a large degree of creative freedom in terms of the design. In order to gather information on cushioning behavior, DEKRA subjected a number of different helmets to impact testing in a non-standardized series of tests.

In order to generate added value, the team deliberately chose to use a test that is not included in the same form in the European standard EN 1078. For the purposes of this test, each helmet was fitted onto a steel test head equipped with measurement technology, positioned at an angle of 30 degrees from the vertical, and hit with a round test specimen weighing five kilograms. The test specimen was dropped onto the helmet from heights of one and two meters. The resulting energy, which was transferred into the helmet, was thus 50 or 100 joules respectively. This load applied at a point occurs in a number of real-life accident situations, for example if the head of the cyclist strikes a solid part of a vehicle during the col-lision, such as the A-column or the edge of the roof above the windshield. Of course, the vehicle’s sur-face geometry would not usually match the hemi-spherical test specimen; despite this, it is still possible to draw conclusions with regard to a helmet’s cushioning behavior based on this type of impact.

For this series of tests, a number of different hel-mets were purchased from a large German online shop; two older, used helmets were also tested. All the conventional bicycle helmets demonstrated an excellent protective effect during the impact tests. The shell and structure of the helmets effective-ly distributed the force exerted by the test projectile at the specific point onto the inside section that touched the head. In addition to this, deformations and breaks in the rigid foam of the helmet shell absorbed energy, further reducing the load that acted on the head.

DURING A FALL, THE HEAD IS SUBJECTED TO HIGH FORCES.

dekra helmet test

The best result in the test was achieved by a modern, high-quality helmet with a built-in Multi-directional Impact Protection System (MIPS). The MIPS was developed to absorb the rotational forces that are generated in the head and brain in case of an impact. In most cases, the cyclist’s head hits the ground at an angle during an accident, rather than vertically. The resulting rotational forces can cause brain damage. The MIPS is designed to counteract this danger and reduce the rotational forces. This is achieved by attaching a moving layer of plastic to the inside of the helmet. This plastic layer can move back and forth by about one centimeter in every direction. The system is generally compatible with any type of helmet, and in theory can also be retrofitted onto conventional models by their respective manufacturers. In the test with the MIPS helmet, the force that acted on the head was measured at 3.8 kN. A model of the same design without the MIPS recorded slightly higher load values of 4.0 kN.

In order to determine how the age of a helmet affects its peformance, a seven-year-old helmet from a discount store was also tested. The force measured when test-ing this helmet was 4.2 kN. A very high-quality helmet that was almost 21 years old achieved a value of 4.5 kN. Two of the helmets for teenagers bought in fall 2019 had been manufactured in January 2018 and December 2016 respectively. The newer helmet achieved a value of 4.9 kN in the test; the older one only 5.4 kN. Another helmet designed for teenagers reduced the load to 4.3 kN.

Another helmet included in the test, which complies with the requirements for speed pedelecs with an electrically assisted maximum speed of 45 km/h, recorded similar results to the regular bicycle hel-mets in this test, with load values of 4.8 kN and 5.1 kN. However, due to differences in its shape it also covers additional impact scenarios and provides good head protection in situations that would push traditional bicycle helmets to their limits.

An airbag helmet included in the test had no effect in terms of reducing the impact. Due to the weight of the falling object, the material of the airbag tore open at a point on the side, causing it to lose the gas inside it, and thus its protective function. Within the frame-work of the tests carried out, it was not possible to ascertain to what extent such behavior would also occur in case of impact against a “sharp-edged” curb, if the wearer’s head went through a shattering wind-shield with the airbag inflated, or if the airbag came into contact with slender but hard vehicle compo-nents such as an A-column during a collision.

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