The Royal Society for the Prevention of Accidents
(RoSPA)
Motorcycling Safety Position Paper - February 2001
7 THE DESIGN OF MOTORCYCLES
7.1 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
approaching 200 mph. Learner riders are restricted to motorcycles
of 11kw power output and recently qualified riders to 25kW for
the first two years.
7.2 The design and construction of motorcycles
can affect both primary and secondary rider safety. The main
primary safety features are the motorcycle’s handling characteristics:
engine power, speed, lighting and braking capabilities. (Other
crucial safety areas are the stability, handling and tyres of
the vehicles. However, there does not appear to be any significant
safety concerns in these areas on modern motorcycles). The main
secondary safety features are leg protectors and airbags.
7.3 Engine Size
7.3.1 A 1988 TRL report used a special STATS19
monitoring project that 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.
7.3.2 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.
7.3.3 New Zealand law restricts motorcyclists
with a learner or restricted licence to riding motorcycles with
an engine capacity of 250cc or less. A recently published study
assessed compliance with the law; whether the risk of an injury
crash was increased for learner/restricted licence holders who
do not comply with the regulations; and whether the risk of
an injury crash increases with increasing capacity of the motorcycle.
A population-based case-control study was conducted over a three
year period from February 1993. It found no consistent pattern
of risk increasing with cubic capacity, and suggested that cubic
capacity is a poor measure of engine power. The findings suggest
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.
7.3.4 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.
7.3.5 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.
7.3.6 Having said that, there is little justification
for manufacturer’s producing such powerful motorcycles (or cars,
of course) which are capable of speeds of more than twice the
maximum speed limit for road use. Recent reports suggest that
manufacturers are considering setting a voluntary maximum limit
of 186 mph on motorcycles. But setting a limit at this excessive
speed does not seem to be a serious attempt to improve rider
safety.
7.3.7 There is on-going research and development
of intelligent speed adaption devices 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.
7.4 ABS (anti-lock braking systems)
7.4.1 Braking, especially in an emergency,
is one of the most difficult tasks encountered when riding a
motorcycle. Errors in braking a motorcycle 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).
7.4.2 TRL research shows that the incorrect
use of motorcycle brakes is considered to be a factor in many
TWMV 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.
7.4.3 ABS brakes for motorcycles have been
commercially available since 1988, and have been fitted to a
limited range of large, powerful and expensive motorcycles.
The cost of these systems means that it is uneconomic to fit
them on smaller, less expensive machines. However, a TRL project
to develop an ABS system for lightweight motorcycles suggests
that it is feasible to produce a cost-effective system for smaller
machines, and three manufacturers have offered small motorcycles
with optional ABS. 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. The DETR believe that ABS
should eventually become standard fitment on all motorcycles.
7.5 Daytime Running Lights
7.5.1 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 1989 (as amended)
currently permit, but do not require, the use of daytime running
lights by any vehicle, not just motorcycles. However, the conclusions
of research into the benefits or dis-benefits of daytime running
lights on motorcycles (and on all motor vehicles) is somewhat
contradictory at present.
7.5.2 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. 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.
7.5.3 A study in Singapore 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.
7.5.4 A report by the SWOV Institute in the
Netherlands 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%.
7.5.5 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. 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.
7.5.6 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.
7.5.7 The UK government currently 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.
7.6 Leg Protectors
7.6.1 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.
7.6.2 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.
7.6.3 TRL research 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.
7.6.4 However, crash tests conducted by the
International Motorcycle Manufacturers Association produced
very 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.
7.6.5 The European Experimental Vehicles Committee
Report on Motorcycle Safety noted that the design and construction
of leg protectors has evolved and improved in recent years.
The DETR believes that research has shown that leg protectors
and airbags (either individually or as a combination) will reduce
accident severity. However, independently tested and appropriate
designs for particular models of motorcycles need to be produced.
7.7 Airbags
7.7.1 Airbags are now well-established for
cars, but research into motorcycle airbags is still at an early
stage. Some research estimates that 25% of serious leg injuries,
and up to 40% of serious and fatal head injuries, might be prevented
by airbags.
7.7.2 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).
7.7.3 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 reasons.
7.7.4 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.
7.7.5 The European Experimental Vehicles Committee
report reviews 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.
7.7.6 Not all research has been so positive.
Some has suggested that airbags may increase injuries, particularly
to the neck.
7.7.7 Motorcycle airbags are likely to be most
beneficial in lower speed impacts, up to 30 mph. As with any
safety system, there will be impacts that exceed the ability
of the airbag to protect the rider. Overall, initial research
suggests that appropriately designed motorcycle airbags may
be beneficial in reducing injuries to motorcyclists, but further
research and development is required to produce effective, practical
and affordable systems. Such research is being undertaken by
both Honda and Yamaha as part of the Japanese Government’s Advanced
Safety Vehicle initiative.
7.8 The Design of Motorcycles - Conclusion
Motorcycles are complex, powerful vehicles that have improved
immensely over recent years. However, some of these improvements
have created new hazards, and there remain a number of areas
where the safety performance of motorcycles could be further
improved.
Forward to "The
environment"
Back to RoSPA Index
Back to "More Stuff"
Index
