EN 1621-4 vs. AMC-013 // Technical comparison of airbag test methods

 

Motorcycle airbags are undoubtedly the greatest evolution in rider safety in the 21st century. However, the market is being flooded with products of unknown quality and performance. How do you know which airbag to choose for your safety?

 

 In 2013, the European Committee for Standardization (CEN) created the European standard EN-1621-4 to evaluate the quality and suitability of mechanically activated inflatable protectors (airbags) for motorcyclists. However, a market study conducted by the Spanish Two-Wheeler Industry Association (see: https://airbag.anesdor.com), shows that only the three oldest brands on the market (AIROBAG, HIT-AIR, and MOTOAIRBAG) comply with EN-1621-4, while new suppliers claim to comply with a protocol called CRITT AMC-013.

 

Why are these products not certified with the European standard?

Are these evaluation tests comparable?

Are products with CRITT certification reliable?

 

To resolve these doubts, we conducted a technical comparison of the energy absorption thresholds required by European Standard EN-1621-4 and Protocol CRITT AMC-013, and these are the results:

  

1.    Starting point: seemingly incommensurable metrics:

 The two standards express impact energy absorption performance in different units, but they are comparable by anyone knowledgeable in the field:

 

The key question is whether they are convertible. The answer is: yes, with precision that depends on the impact dynamics, using Newton's second law.

 

2.    Test apparatus parameters: what both documents specify:

 Both tests use the same impact mass and energy, but the measurement is performed differently:

 

AMC-013 (§5.4.2):

 

• Impact mass: 5 ± 0.05 kg
• Impactor surface: flat circular, Ø 130 ± 3 mm, edge radius 2 mm
• Impact energy: 50 ± 1.5 J (5 kg mass at 1.02 m)
• Impact velocity: v = √(2 × 9.81 × 1.02) = 4.47 m/s
• Anvil: polished steel, 30 × 30 cm, 1 cm thick, with 1.5–2.5 mm leather
• Filtering: CFC 1000 (ISO 6487) — automotive crash test standard
• Measurement: uniaxial accelerometer on the impactor, central vertical axis

 

EN 1621-4 (§5.4.8):

 

• Delegates the apparatus to EN 1621-2 (back) and prEN 1621-3 (chest)
• For back, EN 1621-2:2014 uses: mass of 5 kg, energy of 50 J (same order)
• Force is measured with a load cell under the anvil (force transmitted to the body)

 

3.    The core conversion: F = m × a

 

By Newton's third law, during contact, the force decelerating the impactor is equal and opposite to the force the impactor exerts on the protector and, by transmission, on the anvil:

 

F_anvil ≈ m_impactor × a_impactor

 

This equality is exact under static conditions and introduces a minor error in dynamic impacts on soft materials (the airbag), since the airbag's own mass is negligible compared to the 5 kg of the impactor. The approximation is valid for this case.

 

Conversion of AMC-013 limit:

 

F = 5 kg × 500 × 9.81 m/s² = 24,525 N ≈ 24.5 kN (equivalent peak)

 

4.    Direct comparison of thresholds:

 

We compare the residual force thresholds accepted by EN-1621 at its levels 1 and 2, versus AMC013:

 

Criterion	EN 1621-4 Level 2	EN 1621-4 Level 1	AMC-013
Peak (kN)	3 kN	6 kN	24.5 kN equivalent
Peak (equivalent g)	~61 g	~122 g	500 g (declared limit)
Average (kN)	2.5 kN	4.5 kN	Not specified

First-order conclusion: The peak threshold for AMC-013 is 24.5 kN equivalent / 500 g, which is ~4 times less demanding than Level 1 of EN 1621-4 (6 kN) and ~8 times less demanding than Level 2 (3 kN).

 

5.    The temporal criterion of AMC-013: does it compensate for the difference?

 

AMC-013 §4.8 adds two criteria regarding the shape of the acceleration curve:

 

• Criterion A: no individual peak can exceed 500g
• Criterion B: the cumulative duration of all segments where a > 80g must not exceed 3 ms (and no individual segment > 3.2 ms)

Criterion B is an indicator of prolonged impulse on the chest/back. It can be expressed as a limit on the partial impulse above the 80g threshold:

 

Max. partial impulse = m × ∫a(t)dt ≈ 5 kg × 80 × 9.81 × 0.003 = 11.8 N·s

 

This is equivalent to restricting the airbag from transmitting a sustained force >784 N for more than 3 ms above the 80g level. This criterion is derived from thoracic impact biomechanics (it is related to the Viscous Criterion and the HIC methodology adapted to the torso). It is more sophisticated than a simple peak force limit; however, this criterion does not compensate for the difference in peak demand: a punctual force of 24.5 kN would be biomechanically injurious to the chest regardless of its brevity.

  

6.    Structural differences that limit equivalence

 There are three factors that prevent perfect equivalence even with F = ma conversion:

a)    Impactor geometry: AMC-013 specifies a flat impactor of Ø 130 mm. EN 1621-4 uses an impactor of a much smaller, different geometry (simulating a kerb/platform). The pressure distribution on the airbag is different, which modifies the local inflation dynamics and the transmitted peak force. A flat impactor distributes energy over a larger surface → tends to register lower localized peak pressure but higher total force → not trivially comparable.

b)   Measurement point: AMC-013 measures on the impactor (acceleration); EN 1621-4 measures on the anvil (transmitted force). In highly efficient airbags, there may be a small temporal offset between both signals due to internal pressure propagation, although for motorcycle airbags at 50 J, this offset is usually < 1 ms and clinically irrelevant.

c)    Signal filtering: AMC-013 uses CFC 1000 (up to 1000 Hz). If EN 1621-2 uses different filtering (typically CFC 600 or similar for rigid protectors), the peak values obtained are not directly comparable numerically: a more aggressive filter reduces the recorded peaks.

 

 

7.    Executive summary of the comparison

 

Dimension	EN 1621-4	AMC-013	Equivalents?
Impact energy	50 J (via EN 1621-2)	50 J	✓ Yes
Impacting mass	5 kg	5 kg	✓ Yes
Peak limit	2.5–6 kN	24.5 kN	✗ No — AMC-013 is ~4–8× less demanding in peak
Impulse criterion	No	Yes	Partial — AMC-013 adds a criterion that EN 1621-4 does not have
Metric	Force on anvil (kN)	Acceleration on impactor (g)	Convertible via F=ma with error < 5% for airbags
Impactor geometry	EN 1621-2	Flat Ø 130 mm	⚠️ Potentially different
Filtering	Uncertain without EN 1621-2	CFC 1000 (ISO 6487)	⚠️ Potentially different

 

 Conclusion:

 The two standards are not equivalent or interchangeable. AMC-013 is an approval type protocol with operational criteria that are much less restrictive in terms of peak force.

 A product that passes AMC-013 does not necessarily comply with EN 1621-4 Level 2 — in fact, in percentage comparisons, the energy absorption requirement of EN-1621-4 is approximately one thousand percent (1,000%) higher than that of AMC-013.

Therefore, products claiming compliance with AMC-013 have an impact energy absorption capacity approximately one thousand percent (1,000%) lower than airbags certified under the EN-1621-4 standard. Considering that these technologies are designed to protect vital organs, the use of products not certified under EN-1621-4 and that do not certify protection for both chest and back is not recommended.