1. SE ATS AND RE STR AINTS
Reinventing the
seat and belt restraints. Ta
king this fact
e use of safety sponsive seat
etermin ing factor in th d eceleration-re ty
Comfor t is a d e concept – a enhancing safe
tion, this new and uniqu in g so massively Y
into considera a crash, in do
osition during e N e T H e R L A N D s I M AG E S C O U R T e s Y O F C H A R D s
AFeT
cupant p
– optimises oc CHeL COeN
eN, CHARD
K & mI
s A F e T Y, T H
sKeR
ANK Heem
AU T H O R F R
S
afety systems for seats and
seatbelts are seemingly in
the twilight stages of their
lifecycles, with any
improvements becoming
more costly to implement and less
effective, while all the time increasing
vehicle weight. What is abundantly
clear is that for any significant advances
to be made in the future, an entirely
new approach will have to be adopted.
The Deceleration Responsive
Figure 1:
Seat/Seatbelt, or DRS (codenamed
DRs-Albatross
Albatross) is the result of critical
in most forward
and unbiased analyses of 50 years
crash position.
of dynamic testing experience at
The chest
TNO test facilities in Delft, the
remains behind
Netherlands. This fundamentally
the pelvis
different approach takes into
consideration that comfort is one of
the most important safety aspects. The
compulsory wearing of a seatbelt is not
the same as an occupant wanting to put
on a seatbelt for safety and comfort.
In itself, this requires a lot more effort
from safety engineers – and maybe even
an entirely different philosophy…
The new concept
With the DRS-Albatross concept from
Chard Safety in the Netherlands, the
seatbelt anchorages are relocated from
the sides of the occupant to central
anchorages on the vehicle floor, in front
of and behind the seat (Figure 10).
Essentially, this is a seat integrated
058 VISION ZERO INTERNATIONAL JANUARY 2010

2. within a seatbelt, rather than the other of the concept and promised a fruitful desired level of deceleration (0.8g), the
way around. Deceleration forces are development project. inertia release becomes active. The
more efficiently transferred as a result occupant is then prevented from
of the light yet incredibly strong Seat lock moving forward during braking, and
seatbelt webbing, allowing for three Under normal driving conditions, the moves only slightly in crash position
lightweight seat sections that are free sitting section and backrest are locked but remaining in control of the car as
moving (rotating) in their joints. The to one another. Meanwhile, an ‘inertia the lower legs and eyes remain in the
result of this unique design is an almost release’ for higher deceleration values same position. This effect will be
ideal line of force and optimal use of alters the seat from a solid construction experienced as comfortable and is a
the vehicle’s deceleration. to one with supporting seat sections major safety aspect as the occupant
during a crash situation, if the does not move toward a later inflating
The principle occupants are wearing their seatbelts. airbag. According to papers written by
The seat sections move in a trapezium- As a consequence, what you have is a Waldemar Czernakowski in the early
type action with the front leg and deceleration-responsive seat that also 1990s, [1] pre-impact braking occurs
the backrest being the vertical has the potential to interact with in more than 60% of frontal crashes.
components. The rigid and enforced information available from early With the avoidance of a collision, the
position toward one another is assured warning sensor systems. seat returns to its normal position and
as a result of the webbing of the seatbelt With the electromotor in the seat- supports the acceleration pressure.
being threaded through the frames of adjustment system, some 500ms can be
the seat sections. Under deceleration used for position changes with a non- Crash behaviour
forces, the webbing route lengthens destructive pretension and positioning The crash behaviour of the seat
and provides an excellent opportunity action, as opposed to the occupant can be predetermined exactly, and
to program desired position changes losing control and the destructive is dependent on the characteristics
of the occupant and seat during pretension at some 6-10ms. This of the webbing, film-spool and
decelerations with a desired crash feature comes as a natural result of the elongation. Within the margin
position sequence. Dynamic principle without extra components. of cushion pressure and body
comparison tests (according to The prospect of using this feature deformation, the occupant cannot but
ECE 16) showed the potential in braking is exciting (Figure 8). At any follow the seat sections, so is therefore
“ESSEntially thiS iS a
,
SEat intEgRatEd within
a SEatbElt RathER than
,
thE othER way aRound”
Figure 3:
sitting section
is adjustable
in height
Figure 2: Rear
impact forces
are concentrated
at the front
anchorage, so
no whiplash
VISION ZERO INTERNATIONAL JANUARY 2010 059

3. SE ATS AND RE STR AINTS
only subjected to predetermined forces. Figure 4a and 4b: The forces between the occupant Compulsory seatbelt usage brings
Reaction forces – delivered at the Conventional and seat sections are balanced – in fact, about a responsibility for the safety
webbing loop connection to the rear (top) crash the seat sections are under reverse force. industry. Clearly the goals of Vision
anchorage – can only be translated behavior versus This element proved to be difficult to Zero can only be met if the crash safety
in a larger route length and thus behavior in a understand, but is important when world makes efforts to improve the
only in forward movement as DRs-Albatross considering unbelted rear passengers. comfort of specific safety features.
opposed to higher forces. (above), i.e. The DRS-Albatross principle This new approach makes solving
Clearly, the deceleration of eradicating also provides protection in rear-end problems simply easier and responds
the occupant and the transfer of whiplash crashes. A resisting tongue prevents to any criticisms of the past. Seatbelts
deceleration forces (with the help of the pelvis from moving up and the have done a great job over the years,
the lower body ligaments, i.e. buttocks) run of the seatbelt inward at the but comfort matters and is essential
to the sitting section also causes an shoulder will provide more control in the desire to get people to actually
increase of the webbing route. As the over the occupant. The majority seek the protection of the seatbelt.
sitting section is pulling directly on the of energy absorption will come This new concept actually opens
rear anchorage and is independent from from deformation of the vehicle and up new possibilities.
the forces in the webbing straps to the Figure 5: seat some will come directly from the
occupant, it means that the forces on back stays with deformation of the sitting section and Specific characteristics
those straps are significantly lower. occupant in backrest. The front-end anchorages, The general free space above the
Note also that the vertical forces in crashes, in doing meanwhile, take almost all deceleration vehicle floor increases dramatically,
the spinal cord are substantially so maximizing forces. This is a significant difference but car manufacturers should happily
lower as a result of a more upright space for to anything existing in the field – it is accept the additional carpeting costs.
crash behaviour. occupant behind impossible to overstretch the neck. At first sight, the connection to the
rear anchorage may seem questionable
in terms of access, but in actual fact
it doesn’t really disturb entering
and exiting the car.
Support for the upper legs: Just in front
and above the cross members in the
sitting section, a webbing strap is
placed for strength and preventing
injury during a crash. Together
with the strap section between the
anchorages, it provides very strong
support for the upholstery (Figure 6).
Rebound protection: The outside support
near the head provides extra comfort
in sleeping positions as well as
protection in crash rebound. The
B-pillar poses a serious problem in
off-centre crashes (EuroNCAP).
Seatbelt anchorages: The format
of the lower seatbelt anchorages have
been changed (Figure 7), in that the
webbing is threaded rather than
stitched. Apart from the extra strength
that this provides for the sitting section,
060 VISION ZERO INTERNATIONAL JANUARY 2010

4. SE ATS AND RE STR AINTS
it allows the effective anchor point to
move forwards. Indeed, this makes the “ClEaRly thE goalS of ViSion
system much more comfortable for
children and females. In fact, for ZERo Can only bE mEt if thE
children of school-going age, this
concept can meet the requirements in CRaSh SafEty woRld makES EffoRtS
R44 without booster seats. The large
adjustment of seat height towards the to impRoVE thE ComfoRt of
headrest will be a desirable feature.
Height adjuster: The shoulder strap SpECifiC SafEty fEatuRES”
arrangement seems a great relief for
all engineers trying to accommodate
variations in posture for different-sized the angle of the backrest changes to
occupants. This selected arrangement provide support in sleeping positions
adjusts itself, even in moving sideways. and it prevents sliding ‘down and Figure 6 (left):
Armrest and buckle reach ability: under’, in doing so relieving the tension Upper leg
Although the armrest is reduced in size, required in the lower body to prevent support for
it is nevertheless still effective where it it. From a reasonable sleeping position transfer of
counts – for the elbow and in respect still protection will remain available. deceleration
of sitting down and getting back out No head impact on seatback in front: forces
of the seat. The sitting section is In fact it makes the use of three-point
adapted so the belt buckle can be more seatbelts for seating positions with
easily reached. In fact, there is a large a seat in front quite different. The Figure 7 (left):
space for it in the sitting section. distance between seats can be much Adjustable height
Retraction forces: The retraction forces smaller because there is enough leg for the sitting
and shoulder strap position are major space anyway. In forward crashes the section
reasons that people choose to ignore backrest in front has also gone forward
compulsory seatbelt laws. However, severely and crashing the head onto
in this design, the webbing runs the backrest in front is no longer
centrally between the seatback cushion an issue. For coaches (Figure 5),
and the seat frame, so simply leaning the principle provides much comfort
back will cancel any retraction forces, and safety while savings in weight
while any slight deceleration caused close to 1,000kg. ‹
by braking will restore the retraction
force immediately. References
Headrest position: The lower back Czernakowski, W, The effects
[1]
and sitting construction have become of pre-impact braking on dynamic
one piece. Depending on the length test performance of child restraint Figure 8 (left):
of the occupant, the sitting section systems (CRS) in frontal impacts slight changes
can be adapted, which improves Czernakowski, W. & Otte, D, The of position
the head space as opposed to effect of pre-impact braking on the during braking
adjusting the headrest. performance of child restraint systems
Sleeping: In the selected construction, in real-life accidents and under
the angle of the sitting section versus varying test conditions
eCe 16 pulse
Albatross
Deceleration curve occupant
Deceleration difference occupant/vehicle
Current difference bandwidth in
deceleration differences
Albatross indications:
• Chest displacement 175mm
• Pelvis displacement 140mm
• Force on rear anchorage 33kN
30g
• effective transfer of forces
Figure 10: New
to the vehicle 93% anchor position
Difference in deceleration in
arrangement
pelvis and chest are marginal Figure 9: The makes the
difference vehicle a
in deceleration personal
forces between energy absorber
occupant and
vehicle interior
is reduced
30ms
dramatically
VISION ZERO INTERNATIONAL JANUARY 2010 061