Quad Bikes – Are they really that dangerous?
By Keith Simmons, Managing Director KND Consulting Pty Ltd
Background
According to the Centre for Agricultural Health:
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there were 22 fatalities involving quad bikes in 2015 of which 15 (68%)
occurred on farm. 10 of 20 known crash types were rollovers (50%).
there were 15 fatalities involving quad bikes in 2014 of which 12 (80%)
occurred on farm. 9 of 15 known crash types were rollovers (60%).
There were 21 quad bike fatalities in 2013, 19 in 2012 and 20 fatalities in
2011
In 2012, Safework NSW (formerly WorkCover NSW), on behalf of the Heads of
Workplace Safety Agencies in Australia, engaged the University of NSW’s Transport
and Road Safety (TARS) Research Centre, to undertake the Quad Bike
Performance Project (QBPP). The project aimed to improve the safety of Quad
Bikes and Side by Side vehicles (SSVs) by developing a 5 Star based, consumer
safety rating system for these vehicles when used in the farm environment. The
Australian Consumer and Competition Commission (ACCC) also supported the
project, funding testing of sports type Quad bikes as part of the program.
Over 1000 Static Stability andDynamic Handling tests were conducted in 2013 and
2014 at the NSW Roads and Maritime Services’ Crashlab. Testing was undertaken
on:
 eleven production Quad bikes (8 general purpose or agricultural type Quad
bikes and 3 sport type Quad bikes);
 five production SSVs; and
 one prototype quad bike that had many of the properties the research group
considered desirableof a safer vehicle.
In addition to physical vehicle testing, TARS researchers also conducted a detailed
study of 109 relevant fatalities (from a total of total of 141 Quad bike related deaths
for the period 2000 to 2012) from data obtained from the National Coroner’s
Information System. Approximately 75% of the 109 fatalities occurred on Farms,
making quad bikes the leading cause of injury and death on Australian farms, and
exceeding that of tractors. Injury data from various hospital and other injury
databases was also investigated.
Fatality data indicated overwhelmingly that rollover, pinned entrapment and
asphyxiation are the major casual factors involved in farm place deaths related to
Quad bikes.
So why does a machine, that appears to be stable, end up being involved in so many
serious crashes?
There are some crashes that occur where the rider simply does something really
stupid and places themselves (and others) in danger.
There are other crashes however, where a dangerous combination of poor rider
technique, (often little or no rider training), distraction or inattention and the
mechanical properties of the vehicle combine to cause an otherwise unlikely crash.
The aim of this article is to explain those mechanical properties and link them to the
necessary training and riding techniques, so you can reduce your risks of being
involved in a quad bikecrash.
Is there something wrong with Quad Bikes?
Figure 1Kymco MXU 300 with a Hybrid III Crash Test Dummy (ATD) rider at NSW’s Crashlab
There are a number of mechanical properties that can combine to make Quad Bikes
a dangerous machine in some circumstances.
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Quad Bikes typically have softer front suspension than rear suspension
These suspension settings produce an “oversteering characteristic” (in turns,
the rear end slips more than the front end)
Rear differential is fixed (both wheels rotate at same speed even when
cornering)
Rear suspension is either a rigid beam “swing arm” type or has a torsion bar
connecting independent rear suspension arms
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The softer front suspension and arrangement of rear suspension causes the
vehicle to want to roll over the outside front wheel in turns, with the beam axle
or torsion bar lifting the inside rear wheel up as it does. (without this action,
the rear wheels would want to make the Quad Bike plough straight ahead)
This body roll is actually the start of a rollover motion.
When load comes off the inside rear wheel (reducing tyre drag) the rate of
turn suddenly increases. Unless the rider reduces throttle or rate of turn, or
moves their body to oppose the lateral acceleration (the overturning forces)
the Quad Bike will likely roll over (sometimes even at low speeds).
To counter these effects of mechanical design, it is essential the rider uses an
“Active Riding” method and style. For riding on slopes and in turns, Active Riding
requires:
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Physically shifting your body weight around the vehicle, from side to side as
well as forward and rearwards (when going up and down hills);
Slide your buttocks across the saddle and shifting as much weight as is
necessary to keep the machine stable; and
Adding weight to the inside foot plate.
Figure 2: Quad bike riders performing “Active Riding” as they negotiate curves along a track.
As well as leaning into the turn, the riders must move their pelvis toward the inside of the turn
and shift weight onto the inside foot plate. (image source: www.cape-town-tourism.za.net)
Active Riding is not just leaning into a turn for your own comfort, it is an essential
part of Quad Bike safe operation. Your Owner’s Manual will provide more detail on
Active Riding. Most vehicle manufacturers provide training DVDs as well as some
on-line resources. The safest approach is to undertake an accredited course in
Quad bike riding.
Manufacturer’s Warnings – take heed!
Quad bike manufacturers also warn against riding on hard, paved or sealed
surfaces, to reduce the risk of crashing. Despite this manufacturer’s warning,
Australian farmers have little choice but to ride on relatively hard surfacesthat can
have friction coefficients near that of the conditions the manufacturer’s warn against.
Problem areas include areas like:
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Farm roads and tracks,
Hardstands,
Public roads that connect between paddocks; and
Dry paddock or even dry and matted short grass.
On firm surfaces, the plough effect mentioned above is worsened. The rider thus
has to increase steering inputand when the vehicle does respond and start its body
roll, the reduced drag on the inside wheel causes the vehicle to turn even more
sharply. Without close attention to the riding task and Active Riding, and
somesteering or throttle moderation, there is a higher risk the vehicle will roll over.
On firmer surfaces the rider often has to use “a sawing motion” with the handlebars,
constantly adjusting speed and direction as well as their body weight distribution, to
ensure they follow their desired path and keep the Quad Bike stable. This is also
one of the reasons why carrying passengers is very dangerous and must never be
allowed on Quad bikes that are not specifically designed to take pillion passengers.
Figure 3 Manufacturers warn against carrying pillion passengers for good reason. While
sometimes riders have the best intentions, the consequences are likely to be catastrophic.
The extra load across the rear axle not only increases the plough effect, but can
actually unload the front axle slightly (if the passenger is sitting over or behind the
rear axle), reducing friction at the steering tyres. The rider then has to provide even
more steering input to force the turn and then when the vehicle does respond, the
passenger is unable to shift their weight to counter the roll motion. The passenger
can also restrict the rider from being able to correctly perform Active Riding. The
result is often a rollover crash with tragic consequences.In addition to the dynamic
handling risks, there is no backrest, no proper hand holds and no safe place for the
passenger feet to rest (to avoid entanglement in the rear wheels). Do not carry
passengers on a Quad bike not designed for them.
So is Oversteer a good thing or a bad thing?
There has been heavy debate between vehicle manufacturers and the TARS
research team throughout the Quad Bike Performance Project about the suitability of
having an oversteer characteristic in a farming or workplace vehicle, especially
where the rider will often be distracted or inattentive to the riding task.
Competitive or “spirited” riders will often use throttle control to increase the oversteer
effect, breaking traction and drifting the rear end while cornering. Theythen bring the
vehicle to point toward where they want to go and power out of the corner. This type
of riding may produce the best times around a competition track, but it requires
constant and close attention to the riding task and a lot of physical (Active Riding)
effortby the rider. It is also inherently risky. In the workplace, and especially on
farms, keeping all wheels in contact with the ground is the safest way to ride,
especially when operating alone or out of contact with possible help. A slight
understeer characteristic is more forgiving of any distraction or inattention.
From a vehicle dynamics perspective, Oversteering vehicles:
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turn toward a disturbing force. This means on a side slope, they tend to turn
up-hill instead of downhill;
have a Critical Speed, above which the vehicle will become directionally
unstable; and
increasing rear load shifts the CoG rearward and increases the Oversteer
Gradient, which further reduces the Critical Speed.
Note: Critical Speed is a function of both the Oversteer Gradient (measure of how
much the vehicle oversteers) and the wheelbase1.
Dr Thomas Gillespie2, one of the world’s foremost experts on vehicle dynamic
handling, wrote in evidence to the US Consumer Product Safety Commission’s 3
inquiry into establishing handling standards for Recreational Off-highway Vehicles,
the following two key points:
1V
Crit = √(-K/Lg) (V Crit = Critical Speed (m/sec) K= Oversteer Gradient (Rad/g of lateral
acceleration), L = Wheelbase (m), g = Gravity (m/sec2))
2 Gillespie Thomas D.; Comments on CPSC Notice of Proposed Rulemaking for ROV’s; Advice to the
Recreational Off-Highway Vehicle Association of USA to support a technical submission to the US
CPSC. 8 June 2015.
3 CPSC has a similar role as the Australian Competition and Consumer Commission (ACCC) in
ensuring product safety for consumer goods.
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“Oversteer vehicles can be operated safely as long as they are below critical
speed”, and
“The appropriate engineering inquiry, therefore, is whether the vehicle is
capable of reaching critical speed (i.e., displaying instability) within the
intended or foreseeable use of the vehicle”.
The Quad Bike Performance Project undertaken by TARS made exactly those
engineering inquiries suggested by Dr Gillespie. The project found that even with a
rider less than 80 kg, most Quad bikes had a Critical Speed below 40 km/h and
some even below 30 km/h! Only one of eleven production Quad Bikes tested
displayed an Understeer characteristic and hence did not have a Critical Speed.
Bump Obstacles – another safety risk
The QBPP also designed a bump test, which identified a significant mechanism in
which Quad bike riders can (and apparently do) lose control and roll over. The test
involved going over moderate (150mm) bumps (representing logs, small mounds,
ruts, etc.) at the relatively low speed of 25 km/h. On some vehicles, the rider is
displaced excessively sidewaysafter the rear wheel impacts the ‘bump’. As their legs
are not supporting their weight at this time, the only way a rider can attempt to return
to the saddle is to pull on the far side handle bar, which further exacerbates the turn
of the Quad bike, leading to rollover. If the rider does not let the hand grips go in
time, it is likely they will pull the quad over on top of themselves.
Figure 4: Example of QBPP Bump obstacle test, showing the lateral displacement of the Quad
bike and rider (ATD) on the saddle. Note rear left wheel is airborne as the quad is turning to the
left. If not arrested by the bungy cord, the quad bike would have rolled over.
Once again, close attention to the riding task and an Active Riding style is required to
avoid bump related rollover crashes. The rider must constantly scan for bumps in
the path ahead and when anticipating a bump, as part of Active Riding, raise their
body weight up and balanced on their legs, with slightly bent knees. This allows the
knees to act as shock absorbers, instead of the pelvis being accelerated up and
across by the saddle.
The common theme here is that safe riding of a Quad bike requires constant
attention by the rider and a large amount of Active Riding (both of which are mentally
and physically demanding). Distractions, such as when working on the farm,
increase the risks for Quad bike riders significantly. Many recommendations were
made from the Quad Bike Performance Project, several of the key recommendations
(paraphrased) are:
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All Quad Bike riders must be properly trained before riding,
Children below the age of 16 must never ride an adult quad bike,
Never carry passengers on a quad bike that is not designed for them,
If you do not know how to, or cannot physically perform Active Riding, you
must not ride a Quad Bike, and
Compared to Quad bikes, Side by Side Vehicles (SSVs) are more stable in all
circumstances (i.e. higher resistance to rollover), are more forgiving of lapses
in attention or distraction, require little physical effort by the driverand are less
reliant on the operator’s vehicle handling skills. They also have a rollover
protective structure which, when used with seat belts, improves probability of
rollover crash survival considerably.
The Project recommended a “fit for purpose” assessment be undertaken in the
workplace and where appropriate, Side by Side vehicles should replace Quad bikes.
For further information on the Quad Bike Performance Project, or to access the
QBPP reports, go to: http://www.tars.unsw.edu.au/research/Current/QuadBike_Safety/Performance_Project.html
About the Author: Keith Simmons is an independent consultant in fleet
management, vehicle and road safety. He spent 20 years as an officer in the Royal
Australian Engineer Corps, 7 years as Fleet Manager for NSW Police Force and 5
years as the General Manager Safer Vehicles at the NSW Centre for Road Safety.
In this last role, Keith was responsible for vehicle safety standards, policy and safety
research for all vehicles that access roads in NSW. Since leaving NSW
Government, Keith has led the Dynamic Handling component of the Quad Bike
Performance Project and has undertaken major road and vehicle safety projects in
Qld and Chile for BHP Billiton, the Western Australian Police Force, Pan Aust
Mining in Laos and many more interesting and challenging safety projects. Keith is
currently researching light vehicle rollover safety at UNSW (in his spare time).