Crash Testing a GL1800 Airbag System

Honda introduced the first ever motorcycle airbag system in 2006 as an update, and arguably a considerable upgrade of the GL1800 GoldWing. The design and testing effort which went into this development must have been enormous; getting the balance right, so the Airbag goes off when it needs to but not otherwise, is quite an engineering feat.

Honda’s Airbag System is designed to save riders’ lives and it appears genuinely to have done so on at least one occasion already, but it is an expensive addition and it adds significant extra weight. And is there a risk that it could go off inappropriately while riding, in which a crash would almost certainly be caused.  Is it a vital safety aid, is it worthwhile if you can afford it – or would GoldWing riders be as well choosing (in North America at least, where they have a choice) the lighter, cheaper, non-airbag versions of the GL1800 anyway, regardless of budget?

How can an airbag system work safely and reliably on a motorcycle? Is a single airbag, providing frontal impact protection only, and only for the rider, enough to be worthwhile?  Modern cars are designed to provide very high standards of impact protection to occupants; they have a strong protective passenger “cage” which is protected from impact forces by crumple zones front and rear and by reinforcing bars at the sides.  Within the “cage” driver and passengers are protected from injury by multiple airbags, sometimes nine or more of them.

The airbag's size ensures it cannot push the ride backwards

With a motorcycles neither an enclosing cage nor multiple airbags are really possible.  The whole point of a motorcycle is that the rider sits out in the open, on rather than inside the vehicle’s frame and riders are often thrown off the bike during a crash, as racing circuits spills show only too clearly.

Because of this limitation, efforts have been made to design airbag-type protection systems which are attached to the rider rather than the bike and these systems, having been developed for racing applications, are also starting to be sold for use on the road. How can an airbag system based on a single airbag attached to the bike provide worthwhile protection?

The answer lies in the results of Honda’s research into motorcycle accident statistics.  This showed that a very high proportion of motorcycle injuries, especially serious injuries and fatalities, involve a frontal impact for the motorcycle – well over over 90% in fact.  Typical scenarios include a car pulling out across the path of a motorcycle or a bike leaving the road and hitting an obstacle such as a wall or a tree.

It didn't take long for someone to see the funny side of the airbag's inflated shape

So protecting the rider from frontal collisions would potentially be very worthwhile, even if it is not practicable to do the same for motorcycle passengers  or to protect riders against impacts from other directions.  Hence the design aim for Honda’s Airbag; to mitigate impact and reduce if not eliminate injury to the rider from a frontal collision.

The GL1800 Airbag is therefore designed to protect the rider in the event of a head-on or nearly head-on collision.  It does not set out to protect rider and passenger from all possible injuries.

It therefore makes no sense to judge it against expectations that a motorcycle airbag system should be as effective in providing all round impact protection to all on board as a car’s can be.  That’s blinkered and silly; the value of a motorcycle airbag system lies in whether it can reliably save riders’ lives in motorcycle accidents which would otherwise kill them.

The (basic) Science of Survival

Protection against injury from a collision while in or on a moving vehicle is all about reducing the rate of deceleration of the rider’s vulnerable organs, notably the brain and the heart and its major blood vessels.  Rapid deceleration, within reason and for short periods of time, is not harmful.  But high rates of the application of decelerative forces, i.e. the application of an abrupt jerking force,  even for very short periods of time, can cause fatal injury.

Inflation is almost instantaneous once the ECU decides a collision has occured

Imagine slowing a GoldWing from high speed using hard braking; the brakes, assuming they are serviceable, decelerate the bike smoothly and steadily as well as rapidly. The aim is to establish the highest possible rate of speed reduction (i.e. of deceleration) without high rates of deceleration, ie without violent jolting or jerkiness.  There is no jerkiness at all when braking a GL1800 hard from high speed on an ordinary, smooth road surface, especially if an ABS system is helping out.  The bike just sits down on its suspension a bit and and slows down very rapidly and smoothly.  Jolting and jerkiness when braking hard needs to be avoided; it will prevent optimal braking and it could cause loss of tyre grip and therefore of control.  (Incidentally cadence braking, if that’s what springs to your mind, is not jerky or jolting in the violent way that I’m implying here!)

So if you draw a graph of the rate of speed reduction it would be a relatively straight line; deceleration (the rate of speed reduction, measured as feet per second per second) is rapid but the rate of deceleration (measured as feet per second per second per second) is, once the brakes are full on,  steady.  There is no jolting in slowing down under hard braking; the rider is able to stay in his seat and hang on to the handlebars. Only if the bike hits an obstacle will any jolting occur.

On the other hand if the bike, whether or not already braking hard,  suddenly hits a massive obstacle, such as  a car which has driven into its path, the impact will very abruptly reduce speed and the rate of deceleration, the “jolt effect”, will suddenly become very high. The rider will be at risk of being throw forwards on the bike irresistibly and of injury.  When high rates of deceleration (i.e. severe jolts) occur a rider’s internal organs can be injured even if his outside stays in one piece.  A rider’s jelly-like brain will stay in shape and attached to its mountings inside the skull during controlled braking, even the extreme levels of braking achievable by racing bikes and cars, but violent jolting, such as on impact, can cause the brain to slop around violently inside the skull so that it can get seriously bruised or even come adrift from its mountings.

The critical importance of high rates of change of deceleration (and of acceleration, same effect the other way around) in avoiding injury was discovered when ejector seats were being introduced into new aircraft after WW2.  An ejector seat has to accelerate a pilot very rapidly over a short distance to gain the vertical speed necessary to clear the aircraft’s tailfin before it catches up with him, so it was necessary to incorporate the fastest possible build up of speed from a standing start.  Early seats used what was effectively a gun to achieve this; a five feet long tube attached to the chair was fitted downwards as a close fit inside another one, providing an effective gun barrel length, as the chair lifted off, of ten feet or so.  It was discovered that the size of charge was absolutely critical; too much bang gave too much jolt and compression fractures of the spine occurred.  Later ejector seats used rocket propulsion, which accelerates the pilot more smoothly.

During the same decade head protection was being developed for pilots too.  It was discovered that the outer shell of a helmet needs to resist penetration but it also needs to deform progressively (i.e. to collapse gradually, like a car’s front-end crush zone) on impact as a way of decelerating the head steadily, i.e. avoiding jerkiness.  On modern helmets this is achieved by using hard materials (such as glass fibre or polycarbonate) which will resist penetration but also deform without rebound on impact, together with either an air gap into which collapse of the shell can occur or better still a layer of progressively crushable material.  These days polystyrene is commonly used for this purpose.

The protective value of a helmet depends on the thickness of polystyrene lining, since it is the distance through which progressive crushing can occur which limits the helmet’s protective capability.  Helmets also have to provide adequate visibility and to avoid being so large as to be unwearably cumbersome otherwise, purely for purposes of impact protection,  helmets would be very much thicker.

Another design factor for protection systems is the avoidance of springing or recoil.  So providing a progressive collapsing zone for protection isn’t quite the same thing as cushioning the blow and it cannot be done with closed cell foam materials.  The last thing a rider’s vulnerable organs need, having been brought to a halt,  is to be bounced back in the opposite direction again.  So a springy cushion popping up in front of the rider on impact would be no good at all.  The device  which is used to protect the rider must work like the crumple zone at the front of a car or the pile of cardboard boxes on to which a stuntman falls, hence the use of a collapsing airbag.  These are all chosen because they collapse gradually, absorbing energy as they do so.

These principles, of using jolt-free deceleration over the maximum available distance and the avoidance of recoil are common to all systems of injury protection.  Hence the carefully chosen inflated size of an airbag and its explosive means of inflation (to maximise the distance available for deceleration) and its carefully sized holes, to allow progressive deflation at the optimum rate and thereby rapid but jolt-free and recoil-less  deceleration.

The really clever part

So much is well established safety engineering in cars and has been around for a long time.  Honda’s innovative – and really very clever – bits of the GL1800 airbag system are the combination of sensors (mounted on the front forks) and an electronic control unit which makes the airbag unit go off when it should but not otherwise.  Motorcycles bump into kerbs and suffer other jerky movements, especially a low speed and the last thing a GoldWing rider wants is an airbag going off inappropriately.  It would dropping you bike seem pretty tame in terms of feeling foolish.

The GL1800 Airbag System will not go off at low speed, only when there is a substantial impact at riding, rather than manoeuvring, speeds.  You can view Honda’s official video of the GoldWing Airbag System by clicking here.

As you will see Honda didn’t just test directly head-on collisions and the airbag is shaped to perform well in oblique contact too.

Has it really worked in practice?

As far as I have been able to discover there have been no reports of inappropriate inflation of the GoldWing Airbag System at all.  Only two cases of inflation in a collision have been reported so far on the internet.

Look closely to see there is substantial front end damage; the helmetless rider was uninjured

One inflation occurred in response to what might have been a relatively low speed impact (under 30 mph?) in the USA when a car pulled out in front of the rider.  The rider was reported to believe that the airbag inflation saved him from injury.  He wasn’t wearing a helmet at the time, so it probably did.  The bike can be seen in the photo as having suffered substantial front end damage; the front wheel has moved backwards and so the forks are bent and the front fairing is also displaced backwards too.  This may illustrate something towards the lower end of the impact range within which the system is designed to inflate.

The rider survived hitting a tree at 55mph

In contrast with this the silver bike in the next picture has suffered much more obvious and widespread damage.  Its German rider was reported to have been forced off the road at about 55mph and then hit a big tree full on – which would normally be likely to be an unsurviveable collision for a motorcyclist, even wearing a helmet and proper biking gear.  His bike was a write-off, as the picture shows, but he is said to have escaped with limb fractures and, most importantly, no head injury.

There no published statistics about how many potentially serious injury or fatal accidents have involved GoldWings so statistical evaluation of the value of the GoldWing Airbag System is not possible.  However based on these two inflation occurrences, especially the German one, the airbag seems to me to offer very effective protection.  When I first heard about the German accident I was dithering about whether to change my 2004 GL1800 for a new Airbag Model and it convinced me to make the change.

There is a downside

The Airbag Model is heavier and there is a lot less room for auxilliary wiring under the top shelter and gloveboxes, indeed the right hand side glovebox is lost altogether.

Changing the air filter is a much more complex job too and despite what it says in the Manual, really requires moving aside (rather than removal and disconnection) of the airbag unit.  And you do need to be very careful to disconnect the battery and wait 20 minutes before doing this, or indeed anything which involves connecting or disconnecting or in any way disturbing any yellow connectors!

Overall assessment

I am not concerned that the Airbag System is in any way over-sensitive and might go off inappropriately.  I hit another bike on my previous (non-airbag) GL1800, when he suddenly pulled out of a line of stationary bikes I was overtaking (at about 10 mph while marshalling) and it would be nice to be sure that it would not have gone off in response to that collision.  My GoldWing brushed the other bike (a 1960s Matchless) aside like a toy, throwing its rider off and it to the ground seemingly without even deviating from its line.  My bike stayed perfectly upright and allowed me to bring it to a safe halt, perhaps even while the other bike was still airborn.  The impact was on my lower cowling and engine bars rather than the front wheel or forks so airbag sensors would only have picked up the jolt of the collision indirectly.  I certainly didn’t need an airbag for protection and I’m reasonably confident that, if an airbag had been fitted, it wouldn’t have gone off.

And the test photos and video, and especially the survival of the German rider who hit a tree, give me confidence that my airbag would provide real and valuable protection if I am unlucky enough to suffer a serious frontal collision.  As a motorcyclist, however consistently and carefully you try to look out for cars which might pull out of a side road in your path.  If you miss the opportunity to anticipate that a car at or approaching a side junction might pull straight out and take avoiding action just in case, you will have no opportunity to take avoiding action once it does so.   A video of Spanish Police deliberately blocking a motorbike by driving a car into its path illustrates very clearly that a motorcyclist has no time to take avoiding action at all;  if you would like to view it click here.

In spite of what seems to me to be very good evidence of live-saving protective value, the Airbag Model GL1800 has not sold well in North America, where a range of GL1800 models of varying equipment are offered, and most riders go for the non-airbag models.  Is that wise?  Then again, is it wise to ride without a helmet, even if the Law in some States allows you to choose not to?

So, my GoldWing’s Airbag System could save my bacon one day and I’m very glad I’ve got it.  Would the absence of an airbag system stop me buying a bike which I otherwise I fancied, such as a Honda Deauville for my old age?  Probably not.  But if an airbag system is an option on a bike I like, I would certainly want to have it.

Indeed, I’m so convinced of its potential value that I toyed with the idea of getting an “I love my airbag” sticker.  But I then I realised it could be misinterpreted and she might think I was referring to her – and that really would lead to a fatal injury.