Page 576 - Automotive Engineering Powertrain Chassis System and Vehicle Body

Vehicle safety C HAPTER 17.1

and comfortable throughout his journey, and thus mini-
mising fatigue.
Also important is his view of the four corners of his
car. Radar devices to indicate the proximity of obstruc-
tions have been suggested. However, even if they could
be offered at acceptable costs, their effectiveness in
traffic moving at even relatively modest speeds would be
open to question. Drivers’ rear view mirrors in many
instances fail to cover a range of vision wide enough to
include cars overtaking from all possible angles. On the
Without VSC With VSC nearside, the view through the mirror should include the
nearside wheel, for ease parking, as well as the road
behind. In general, mirrors should not be so wide that
they are in danger of being struck by the mirrors of
passing cars or other items such as gate posts. Although
some of the points raised here are relatively unlikely
Fig. 17.1-19 Left, diagram showing the path typical of an
understeering car driven beyond the limit of adhesion of the themselves to cause accidents involving death or injury,
wheels on the road compared with, right, one driven in the same they are relevant as regards driver fatigue, which can have
manner but equipped with vehicle stability control. serious consequences.
Driver fatigue is affected by, among other things, the
jacks keep the body at all times at a constant height and climate: in cold countries, an electric seat warming
attitude relative to the road. Some of these systems system may be desirable, but when it is very hot, venti-
dispense with suspension springs. However, it seems lation of the seat cushion and squab, as well as the saloon,
more likely that those used in conjunction with them will may be more appropriate. Air conditioning is even better,
ultimately preferred since, if the static weight of the car and can remove the need for seat conditioning in any
is supported by springs, malfunction of the hydraulic climate. In hot countries, air conditioning is generally
jacks and their control system would not be so cata- regarded as essential, as also, of course, is interior heating
strophic. In general, active suspension has the advantage and ventilation in cold conditions.
of utilising to the full the tyre performance potential.
However, it is costly, it consumes energy and its dura-
bility and reliability remain open to question. Conse- 17.1.21 Seating
quently, for general application, its future would appear
to be in doubt. For seat comfort, the more uniform is the pressure dis-
tribution over the cushion the better. This calls for
measures to offset the natural tendency for the pressure
17.1.20 Ergonomic considerations
to be highest under the hip bones and lowest beneath the
and safety thighs and coccyx, or tail bone. Even so, too high a pres-
sure under the thighs may restrict the blood circulation
Since ergonomic measures are taken before the accident, to the legs and thus lead to severe discomfort after
we shall categorise them as active. The driver’s seating a short period at the wheel. On the other hand, too little
position is of prime importance, in that he has to use his support in this region can cause strain and tiredness of
eyes to obtain at least 90% of the information he needs the legs.
for driving safely. As regards the position of the seat As regards the squab, the most important re-
itself, this must be such that his view of the scene outside quirement for comfort is support for the lumbar region
the car is obstructed as little as possible by components of the occupant regardless of his or her size and,
such as rear view mirrors or windscreen pillars; similarly preferably, this support should be adjustable. Appro-
his view of the instruments, switches and other controls priate selection of the shape and position of the lumbar
must be clear; at the same time, he must be able to reach support can also reduce some of the pressure on the
all his controls easily, with a minimum of effort, and cushion. Provision for adjustment of the angle of the
without being distracted from what is happening on the squab is, of course, also highly desirable. Another re-
road ahead. Visibility of indicator and warning lamps quirement, and one that is not widely appreciated, is
under brilliant sunlight is a consideration sometimes cushioned, yet firm, support for the lower end of the
overlooked. All controls should be easy to operate, and spine, just above the coccyx. It is in this region that
instrument and other indicators easy to read. In other spinal damage is most likely to be sustained in the long
words, the aim is at enabling the driver to remain relaxed term as a result of wear and tear. Because of variations

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