Glancing Off: The Science of Head Protection

Sep 14, 2021 View Comments by

Protecting your noggin is more than a fashion statement.

Written by: Jeff Buchanan.
Photos by: Arai & Brian J. Nelson


In motorcycling, there is no piece of safety equipment as critical as the helmet. Helmets protect the essential gray matter of the human brain, the stuff that makes up our character, preserves our memories, grants us speech, motor actions, vision, hearing, and virtually all thought processes. Essentially, helmets protect who we are.

The key to a helmet’s protective qualities is its ability to stand up to “impact energy.” This is the inherent energy created upon impact, which the helmet absorbs in a variety of ways—primarily with the shell deforming against the impact forces and the inner liner cushioning against the pressure of the wearer’s head as it moves inside. Ultimately, the effectiveness of a helmet is in its ability to disperse the energy generated by an impact, keeping it away from the head inside. This destructive process can be interpreted as the helmet doing its job.

Delving deeper into the science of energy absorption, there’s the helmet’s ability to slide past or glance off of objects, which can dramatically reduce the amount of energy being sent directly into the helmet. This effect disperses as much of the energy sent into the helmet as possible without stopping and is unsurprisingly known as “glancing-off.”

The most common motorcycle accidents result in the helmet receiving an impact from an oblique angle (as opposed to a 90˚ angle). In this regard, when the head strikes the ground off-center, the helmet moves past the impact point, sliding across the crash surface. Provided the energy isn’t directed at the center of the helmet, and the liner provides a decent amount of energy absorption, this sliding action minimizes the impact energy being transferred to the rider’s head. Glancing off works in concert with energy absorption as the two halves of energy management that define head protection.


Helmet certification involves various direct impact and penetration tests, yet doesn’t set any criteria for glancing-off capabilities. Trying to establish what angles to test for and the degree of impact force make it especially difficult to create a truly standardized test. By the simple laws of physics governing movement, all helmets will respond to glancing off to some degree. However, how well they respond to controlling that energy varies greatly depending on construction, materials, design, and finish.

In the carefully-worded arena of marketing, where it is paramount to never introduce anything remotely negative, we have to give kudos to Arai Helmets for openly acknowledging the dangers that exist with riding motorcycles. Arai chooses to openly address the reality of risks, choosing to promote how best to guard yourself against them. This approach stems from Arai’s advanced research and development in helmet design. The company is focused on discovering innovative ways to further the science of head protection.

Arai’s approach to creating helmets that excel in their capabilities to manage energy impact is to prepare for situations that “far exceed their imagination.” Glancing off is a focal point for the company, with Arai developing strong helmet shells that feature smooth, round surfaces that enhance the helmet’s ability to prevent energy from entering the helmet and getting to the rider’s head.

Because there is no general guideline to comparatively test glancing off, Arai engineers rely on their own experience and expertise in studying the aftermath of impacts, setting their own standard. Through experimentation and research, they have come to understand that smoothness is a critical aspect of glancing off, as it prevents the helmet from snagging on the crash surface. The round, egg-shape properties of Arai helmets, inspired by nature’s strong design—which exhibits unusually high resilience to impacts—are free of any exaggerated shapes or hard edges. They combine a strong shell with smooth paint finish, which contributes to their glancing off capabilities.

Additionally, any ventilation parts are designed to break off in the event of a fall to prevent snagging, avoiding a disruption to the shell’s ability to slide. Even the face shields used on Arai helmets are designed to maintain the continuous, smooth shape of the helmet shell for uniform strength, improving the helmet’s ability to glance off.

The helmet shell’s strength is another aspect of providing good glancing-off properties. The less a shell deforms, the better its ability to slide. Arai is dedicated to creating the sturdiest helmet shells by utilizing their complex laminate construction (CLC), which provides incredibly lightweight strength. Arai helmets employ Super Fiber Belts to reinforce critical edges, which operate like barrel rings to prevent cracks from spreading in an impact. Even the resins used on the shell add to the helmets’ glancing-off properties.

Arai’s commitment to creating the world’s best helmets stems from their understanding of the dangers of motorcycling. They’ve risen to the challenge of moderating the risks by crafting helmets that take advantage of ever-evolving technologies and materials. The bottom line is that it’s all about saving your precious head, and ultimately, the things in your head that make you, you.


Tags: Categories: News