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THE
ROYAL SOCIETY FOR THE PREVENTION OF ACCIDENTS
MOTORCYCLING SAFETY POLICY PAPER
JUNE 2006
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MOTORCYCLE
DESIGN
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Improvements to the design and construction of cars over the
last 10 or 20 years have resulted in very substantial reductions
in deaths and injuries on the road. This has not been the
case with changes to the design of motorcycles.
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Engine
Size
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The
term motorcycle encompasses a wide variety of vehicles, from
small low-powered mopeds and scooters to large, high powered
motorcycles capable of reaching speeds of 200 mph and more.
The In-depth study of motorcycle accidents59 showed that riders
100 – 250 cc motorcycles tended to be younger and riders of
500 cc and over machines tended to be older riders. Riders
of motorcycles of 600 cc and above were more likely to be
involved in crashes on bends, and riders of motorcycles with
900 cc and above were more likely to be involved in overtaking
or filtering accidents.
The TRL study of motorcyclists deaths between 1994 and 200260
found that large motorcycles were more likely to have travelling
excessively fast than smaller motorcycles, and their riders
were more likely to have been riding poorly, before their
fatal crash. Riders of smaller machines were more likely to
have judged their own path poorly.
A 1988 TRL report61 recorded the engine size of accident-involved
motorcycles between 1984 and 1986, along with National Travel
Survey data and data on the number of registered motorcycles
to explore the relationship between engine size and casualty
rates. There were marked differences in the use of motorcycles
of different engine sizes. Larger machines did more of their
mileage on non built-up roads, tended to be ridden by older
riders, were more likely to carry pillion passengers and were
used more in the Summer than the Winter months.
The study found that accident rates per kilometre travelled
fell with increasing engine capacity, possibly because larger
machines tended to be used by more experienced riders. However,
riders of larger machines were more likely to be killed or
injured than riders of small machines. In particular, increased
engine size was associated with a higher proportion of accidents
and casualties on non-built up roads. Riders of more powerful
motorcycles also tended to have a higher proportion of accidents
at night, and while going ahead on a bend or while overtaking.
New Zealand law restricts motorcyclists with a learner or
restricted licence to riding motorcycles with an engine capacity
of 250cc or less. A study62 of its effects found no consistent
pattern of risk increasing with the cubic capacity of the
motorcycle, and suggested that cubic capacity is a poor measure
of engine power. The findings suggested that if cubic capacity
was to remain the sole basis for restricting learner and restricted
licence holders, consideration should be given to having a
substantially lower capacity than 250cc.
In the 1960s and 1970s, most sports motorcycles were capable
of producing 40 - 50 bhp with top speeds of 115 -120 mph.
Today, outputs of 75 - 90 (even 130) bhp, with top speeds
not far short of 200 mph, are quite common. It is inevitable
that many riders will want to use the machine’s maximum capability
and to test their vehicle’s limits. Even within legal speed
limits, such powerful machines require exceptional levels
of skill.
In the early 1990’s a proposed European Commission limit of
100 bhp on motorcycles failed, partly because it was not possible
to demonstrate a link between bhp and accident risk. Therefore,
it was not possible to show that imposing a limit would reduce
the number of motorcycle accidents.
Having said that, there is little justification for manufacturer’s
producing such powerful motorcycles (or cars, of course) that
are capable of speeds of more than twice the maximum speed
limit for road use.
There is on-going research and development of intelligent
speed adaptation for cars that would limit their top speed
to the speed limit of the road on which it was driving. This
development process could also be applied to motorcycles,
although any such devices will need to be specifically designed
for two-wheelers and not simply transferred from four wheel
vehicles.
Braking
Braking, especially in an emergency, is one of the most
difficult tasks encountered when riding a motorcycle. Errors
in braking can easily lead to skidding, capsizing or the vehicle
becoming unstable. Front and rear motorcycle brakes are usually
operated separately (unlike a car’s which are linked) and
so the rider has to decide which brake to apply, when and
what proportion of front and rear braking to use according
to the situation and road surface (some motorcycles do have
coupled brakes). Some manufacturers are now fitting Combined
Braking Systems (CBS) that operate both brakes and distribute
the braking force to the front and rear wheels to improve
stability when braking
TRL research12 shows that the incorrect use of motorcycle
brakes is considered to be a factor in many motorcycle accidents.
Over a third of riders used only the rear brake and 11% used
only the front brake. Even in an emergency, 19% of riders
only used their rear brakes and 3% only used their front one.
One study estimated that correct braking, using the full braking
capability of the motorcycle, could prevent 30% of motorcycle
accidents, although this study was conducted before ABS was
available for motorcycles.
ABS
ABS brakes for motorcycles have been commercially available
since 1988, and are now being fitted to a wide range of machines.
It should be noted that the characteristics of braking systems
for motorcycles are different from those of cars; and in particular,
it is not possible to steer when applying ABS brakes on a
motorcycle.
It is important to ensure that riders understand how advanced
braking systems work and receive training in their use. Training
courses to help riders to become accustomed to ABS technology
and its advantages should be encouraged. For example, a scheme
similar to the Bosch ESP-erience could help in raising the
awareness.
Publicity needs to encourage riders to invest in machines
with ABS to help the spread of this technology. A high level
of fitment of ABS should be seen as an important step forward
in motorcycle safety in future. The government would like
to see wider implementation of these systems on all motorcycles.
Daytime Running Lights
Drivers involved in a collision with a motorcycle often
claim that they did not see the motorcycle. It has been suggested
that motorcyclists should be required to use their headlights
during the day as this may help to reduce accidents. The Road
Vehicles Lighting Regulations permit, but do not require,
the use of daytime running lights by any vehicle, not just
motorcycles. However, research into daytime running lights
on motorcycles (and on all motor vehicles) is somewhat contradictory
at present.
In tests of motorcyclists’ daytime conspicuity64 the best
results were from motorcycles using a 40W large headlamp (dipped)
or a pair of daytime running lights.
A review of literature on the effectiveness of daytime running
lights for motorcycles is contained in the European Experimental
Vehicles Committee report on motorcycle safety.11 It states
that a study in four US states showed a reduction of 41% in
accidents during daytime following a law requiring daytime
use of motorcycle headlights.
A study in Singapore65 found that the introduction of daytime
running lights for motorcycles in 1995 has reduced the number
of fatal and serious injury accidents, although had no significant
effect on slight accidents
A report by the SWOV Institute in the Netherlands66 indicates
that the introduction of daytime running lights in Austria
reduced motorcyclist casualties during the day by 16%, and
estimates that the Europe-wide introduction of a similar law
would reduce motorcyclist casualties in the EU by around 7%.
However, road trials by TRL in the early 1990s found that
over 70% of motorcycles in Great Britain were fitted with
headlamps that were ineffective as a conspicuity aid either
by day or night.12 This suggests that there would be little
benefit in motorcycles using their normal headlights during
the day. Specifically designed daytime running lights (separate
from the normal headlights) may be more effective.
Some motorcycle manufacturers are now fitting automatic headlamp
on systems so that the motorcycle’s lights are always on,
a move which RoSPA supports.
Some countries are considering the mandatory introduction
of the use of daytime running lights for all vehicles. However,
there is concern that this may adversely affect motorcyclists,
in that if all vehicles use headlamps during the day, the
relative conspicuity of two-wheelers will be reduced.
The Government has no plans to introduce mandatory daytime
running lights for motorcyclists or for all vehicles, and
would only consider this option if it was supported by evidence
of its likely effectiveness, and after considering any increased
environmental costs (in CO2 terms) due to the energy to power
the lights. However, the Highway Code does advise motorcyclists
that using dipped headlights in daylight may increase their
conspicuity.
Leg Protectors
Leg injuries account for approximately 60% of serious injuries
to motorcyclists, and frequently lead to permanent disability.
Leg protectors have been suggested as a way of reducing such
injuries. Leg protecting fairings have been shown to reduce
injuries but may also alter the motion of the motorcycle during
and after an impact and it is, therefore, important to ensure
that any changes proposed do not increase the risk of injury.
Research has resulted in contradictory claims for the efficacy
of leg protectors, with some studies suggesting that they
would reduce leg injuries, but others suggesting that they
might even increase the risk of other injuries.
TRL research12, 67 over a number of years has investigated
whether leg protectors would significantly reduce the incidence
and severity of leg injuries to motorcyclists. Crash tests
of different types of motorcycles, with and without leg protectors,
were designed and conducted by TRL. They concluded that leg
injuries would have occurred in 55% of the crash tests on
motorcycles without leg protectors, but in only 12% of those
with leg protectors. They also concluded that the leg protectors
used would not have increased the risk of head injuries, and
in some cases actually showed potential for reducing them.
However, crash tests conducted by the International Motorcycle
Manufacturers Association11 produced different results, in
which leg protection was found to be beneficial in three out
of eight pairs of tests, but detrimental in five pairs of
the eight tests. Overall, this study concluded that leg protectors
increased the net risk of head and leg injuries. A later series
of tests by the same organisation found that leg protectors
were beneficial in 2 out of 7 tests, detrimental in 4 out
of 7 test and made no difference in one test. Further tests
by TRL reached the opposite conclusion, finding ‘substantial
benefits’, and recommended further development and research.
Airbags
Airbags are well-established for cars, but not so for motorcycles.
Some research estimates that 25% of serious leg injuries,
and up to 40% of serious and fatal head injuries, might be
prevented by airbags.
There are many problems with applying airbag technology to
motorcycles. The riders and vehicles vary widely in mass,
the seating position of the rider, and the diversity in motion
of both the rider and motorcycle, will all affect the outcome
of the collision. There can also be compatibility problems
between the airbag and the rider’s helmet, due to helmet shapes
also having wide design variations, which can result in a
severe neck injury.
Airbags in cars are designed to absorb impact, whereas motorcycle
airbags need to absorb (or partially absorb) impact and influence
the trajectory of the rider (in order to raise the rider’s
head above the edge of the car roof and to direct the rider’s
body upwards to reduce the impact against the side of the
car).
Motorcycle airbags need to be deployed more quickly (within
the first 20ms of an impact) than car airbags and the impact
detection systems that trigger a car airbag cannot be used
on motorcycles for various reasons11.
Motorcycle accidents involve a wide range of impact configurations,
including frontal impacts where the motorcycle strikes an
object head-on and side impacts where a vehicle strikes the
motorcycle. Motorcycle airbags are likely to be useful in
collisions of a motorcycle into the side or rear of another
vehicle, and in oblique angle impacts.
The European Experimental Vehicles Committee report69 reviewed
a range of impact tests in which medium sized motorcycles
were run into cars. Where airbags were not used the head of
the dummy impacted against the edge of the roof. In tests
with airbags the change in trajectory meant that head contact
with the car was avoided completely, and the motorcyclist’s
body deflected into a higher movement path.
Not all research has been so positive. Some has suggested
that airbags may increase injuries, particularly to the neck.
However, technical solutions will be developed. Eventually,
sensors will record the rider’s position and weight and the
impact speed, so that an adaptive airbag would deploy to protect
the rider if the circumstances warranted it, having taken
these variables into account. Airbags have the potential to
reduce the severity of head, neck and torso injuries, which
are the areas of a motorcyclist’s body that are most at risk
from suffering a fatal injury. When the technology is ready,
manufacturers should be encouraged to fit airbags as standard
through the range of bikes.
Tyres
The tyres are the only part of the motorcycle in contact with
the road. The type and condition of tyres on a motorcycle
have a significant effect on the vehicle’s handling, steering,
cornering, braking and stability. It is essential that the
correct type of tyres is used and they are kept in a good
condition at the correct pressure all the time and replaced
as soon as necessary.
Many manufacturers recommend specific tyres for their motorcycle.
This ensures that the most suitable type of tyre for that
particular machine is used, and riders should always use tyres
recommended by the manufacturer when replacing them. It is
also important that the tyres are suitable for the speed capability
of the motorcycle and its load capacity.
Tyres need to be kept at the correct pressure (which may vary
depending on whether a pillion passenger and/or fully loaded
panniers are being carried). Over-inflated or under-inflated
tyres will affect the safe handling of a motorcycle and may
contribute to an accident. Tyre pressures should be checked
at least once a week. Good tread depth is also crucial, especially
in the wet. In the UK, the minimum tread depth for motorcycles
over 50 cc is 1mm across ¾ of the width of the tread pattern
and visible tread on the remaining ¼. For motorcycles up to
50 cc, all groves of the original tread pattern must be visible.72
However, it is also important to replace tyres before they
reach the minimum tread depth, and many have tread wear indicators
in the tyres to show when the tyre should be replaced. Tyre
manufacturers recommend a minimum tread depth of 2 mm
A concern increasingly expressed is that there appears to
be a thriving after-market of products and services to help
motorcycle owners adapt their motorcycles after they have
purchased them. These adaptations often significantly change
the capabilities and handling of the machines, which the rider
may not fully understand or e able to cope with in all situations
Motorcycle Design - Conclusion
Motorcycles are complex, powerful vehicles that have improved
immensely over recent years. However, some of these improvements
require further development and there remain a number of areas
where the safety performance of motorcycles could be further
improved.
In its Motorcycling Strategy, the Government has said that
it will consider the potential for a consumer information
assessment programme for motorcycles to assess whether it
might lead to improvements in motorcycle safety in the way
that the EURONCAP programme has led to significant improvements
in car design.
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