SAFETY FOLLOW-UP DUMMY; SFD
Author: Sverker Dahl
 

 Project work for the course Technical Traffic Safety (IPE080)
Spring semester 1997
Supervisor: Anna-Lisa Osvalder
 

 ABSTRACT

 The distance between a wrecked car and those who rode/were injured/were
killed in it is more often than not great, in geographical as well as
theoretical terms. Therefore, in a crash investigation, it is difficult to
form a true picture of how the interior of the car relates to the injuries
sustained by the travellers. The author's many years' experience in, with
very simple tools (a skull on a stick or a dummy designed for resuscitation
practice), identifying which part of the car's interior has caused a
certain injury, points at the need for a tool, a dummy that works in
practice. Contacts with experts from the car industry and documentary
research show that no such tool or dummy exists. Dummies used in crash
tests performed in laboratories can not be used for real life crash
investigations because they are both too heavy and too expensive. The aim
of this project was therefore to construct a simple tool to bridge the gap
between the vehicle and people injured or killed therein. The purpose is to
enable the crash investigator to, by means of the dummy, reproduce a true
picture of what took place in the vehicle at the moment of impact and
identify all essential personal injuries related to the interior. The
dummy's spine, arms and legs can be adjusted in length, shoulders and hips
in breadth and chest in width, making it possible to, with relative ease
and precision, adjust the dummy to mimic each person occupying the seats of
the vehicle. Even if the dummy's construction and degrees of motion in
joints and seams resembles that of the human body, it is for technical
reasons stiffer, with a more limited range of motion in shoulders and hips
as well as a spine that is rigid laterally. The dummy can not show the
dynamic course of events but can give an on-the-spot account of the moment
when the personal injuries occurred.
 

INTRODUCTION

 Continuous and systematic crash investigations of the kind that are carried
out after each aircraft crash are extremely rare in the automotive field.
For that reason, information may have been lost that could have been used
to improve the safety of a new car that shows weaknesses that have not
appeared during crash tests in a laboratory environment. Or information
that could have been the basis of recommendations on how additional
equipment (car phones, fare meters, components of audio systems) should be
installed.

Certain car manufacturers and the Swedish insurance company Folksam
constitute the exceptions from the rule that car crashes are not
investigated. Mercedes-Benz, Saab, Volvo and Toyota's Swedish distributor
examine in detail locally occurred crashes where their own make of car is
involved. Folksam analyse wrecked cars which are insured with the company
(as well as the wrecks' counterparts). Inquiry among those in a leading
position within the field of crash safety give an unequivocal picture of
the interest displayed by the authorities: Individual cases of major car
crashes are investigated but no continuous follow-up occurs.

It does, however, occur that the authorities (e. g. the former Swedish
National Road Safety Office, now the Swedish National Road Administration)
choose to look into crashes that occur during a limited period.
Collaboration between the authorities and insurance companies and/or the
car industry has also happened in the USA,  Australia and France.

One exception to the rule about lack of continuity and systematics where
crash investigations are concerned is the work that Gerhard Voigt, formerly
professor at the Institute of Forensic Medicine, University of Lund,
Sweden, was responsible for. In the late nineteen sixties, through the
seventies and early eighties, professor Voigt and the author jointly
investigated fatal car crashes in southern Sweden (south of a linedrawn
between Gothenburg and Stockholm via Jönköping).

The investigations comprised all fatal crashes where the autopsy had
indicated that something in the car or its construction had caused the
lethal injury or injuries in a way that was not previuosly known from the
police report or understandable or recognizable.

Only in exceptional cases was the scene of the crash inspected. As a rule
the car wreck was examined where it had been towed after the crash;usually
a car repair shop or police station.

To facilitate the task of putting the victims' injuries in relation to the
interior of the car, professor Voigt had made a simple tool out of an
adjustable stick with a skull on top. The author later developed this tool
by adding a chest made from wire fencing.

In addition to this simple tool, reports including measures of length and
photographs from the post-mortem were at hand.

Even this unsophisticated equipment gave some clues to what had happened
inside the car when deformation and intrusion took place.

As chairman of the Automotive Committee of the Swedish Emergency and First
Aid Association (Svenska Räddnings- och Akutvårdsgruppen,SRAG) SEFAA
(interest organization mainly for ambulance personnel), the author
continued during the nineteen eighties to investigate crashes where
personal injury was sustained and ambulances were involved in the crash. In
connection with these investigations a completely different kind of dummy
was sometimes at hand, a dummy for resuscitation practice; Resuscitation
Anne. These were sometimes used to get a clearer picture of what had
happened during the crash.

However, neither the skull on a stick nor Resuscitation Anne were suitable
for the task.

The expensive, heavy and technically complicated crash test dummies used in
laboratories can not be utilized for investigations of this kind.

The need for a dummy, a measuring instrument for crash investigations, is
and has long been evident.

The author's supervisor Anna-Lisa Osvalder, Ph. D., Ass. Prof. in
Biomechanics/Ergonomics at the Department of Injury Prevention at Chalmers
University of Technology in Gothenburg, who has recently done documentary
research on the subject of dummies has not found any references other than
to crash test dummies designed for use in under controlled circumstances.

The author therefore chose as the subject of his project to design a simple
tool, a dummy for crash investigations: Safety Follow-up Dummy, SFD.
 

EQUIPMENT AND METHODS

 The aim has been to design a dummy that is
- made of simple materials, available over the counter
- adjustable and anthropometrically correct
- easy to handle.

To attain this, the following material was used:
- beechwood, 50 x 50 mm beam
- front axle parts (steering pivot pins) from Saab and Opel
- tools, flexible screwdrivers
- fixbolts with thumb-nuts.

The author, supported by the preliminary project plan, presented the aim
and objective of the project to Sven Hansson, managing director, and Ronny
Lindell, master mechanic and supervisor, of Hejde Ambulanser AB in
Kävlinge, Sweden. Through their obliging support in putting their resources
at disposal, the work could commence immediately and be finished in time.

The author is single-handedly responsible for the construction of the
dummy, from idea to finished prototype, and has also hand-crafted many
parts of the dummy. Ronny Lindell has been responsible for complicated
parts that demand special skills and experience from joiner's tools that
were used to make the dummy.

Co-workers at Hejde Ambulanser AB and people in the author's set of
aquaintances has made up the standard for the dummy's dimensions. The dummy
was originally intended to be adjustable between 1.5 and 2.05 metres, but
the final version of the "vertebrae" of the spine makes it possible to
lengthen it infinitely.

Each part that has been sketched, discussed and made has as far as possible
been designed to imitate the human body. To make it stable enough for
frequent use in practice, solid materials have been used. On the wooden
beams that constitute the major part of the dummy, measuring scales can be
attached as can stickers to indicate injuries.

The dummy has, in a near-completed state, been shown to professor Voigt,
who judged it to be very well made, well functioning and representative as
a substitute for an injured occupant of a car.

The dummy's chest, hands and feet can be bent far beyond the degree of
tolerance of the human body to show how fractures have arisen. The rest of
the wooden skeleton and the joints lack this possibility.
 

RESULTS

 The dummy is designed to be adjustable in height between 1.5 and 2.05
metres, but since the spinal "vertebrae", which are between one and six
centimetres high, are interchangeable, the dummy can be lengthened far
beyond that if needed.

The chest measurement can also be increased indefinitely, owing to the
choice of flexible screwdrivers to imitate the ribs.

The head is movable in all directions, including translation in the
horizontal plane.
 
 Measures

	Max length (cms)	measure of adjustability
upper arm	26	6
forearm	36	10
femur	54	8
lower leg (including foot)	65	18

 
Range of movement

	horizontal	horizontal
	flexion/extension (°)	abduction (°)	(°)
shoulder joint	10	5	360
hip joint	45	30	360
ancle joint	360	360	dorsal flex 15
			plantar flex 15
elbow joint			115/0
knee joint			115/0

 
 
DISCUSSION

 As there is no other dummy or measuring tool presently available for crash
investigations, there is nothing to compare this Safety Follow-up Dummy
with. On the other hand, the author has made sure that the dummy will be
tested and validated by Volvo's Traffic Accident Investigative Team,
Gothenburg and by Folksam Auto, Växjö, Sweden where the insurance company's
technical division performs all post-crash investigations that form the
basis for Folksam's rating of cars with respect to crash safety.

The dummy turned out mainly as intended, except the shoulder part which
turned out wider and is difficult to make any narrower without losing the
adjustability. The dummy also proved to be heavier than desired, chiefly
owing to the weight of the front axle parts that constitute some of the
joints.

Neither before, during nor after the realization of the project had the
author expected the dummy to fully imitate the human body and its pattern
of movement. For example, skeletons used for educational purposes have
double hooks for shoulder joints. That would have been the most obvious and
simple solution for the dummy, but the author very consciously chose a
joint with a limited range of movement but greater exactitude. Use in crash
investigations requires high anthropometric accuracy.

By focusing on making the dummy simple and inexpensive to produce, the
costs have been kept at a very moderate level. It should also be possible
to start serial production with a moderate set of joiner's tools.

The intention to make the dummy both easy to use and to stow away for
transport has also influenced the work. All adjustable parts have built-in
scales except the chest. The spinal "vertebrae" are easily interchangeable
in order to vary the length of the torso and other variable parts are
tightened by hand with wing-nuts. The head is movable in all directions
except vertically. On the prototype there is an element of risk of getting
one's fingers caught, but since all surfaces would have to be tooled to an
acceptable finish in serial production that problem would diminish greatly.
 

CONCLUSION

 Awaiting the results of testing and validating the dummy in "field" use, no
conclusions may yet be drawn.
 

RECOMMENDATIONS

 Now that, for the first time, a dummy for use in real-life crash
investigations exists, insurance companies ought to take the opportunity to
let their crash inspectors supplement their examination of the vehicle by
looking into what happened in the car at the moment of impact.

It is the author's firm belief that such information could be conducive to
a better understanding of what happens in car crashes and earlier than is
the case now see how certain part of or piece of equipment in the vehicle
causes injury.

This does, however, require a system based on the the patient's
measurements being recorded as he or she is admitted to the hospital. In
most cases the patient's height is sufficient since the other measurements
can be found in templates and the dummy adjusted accordingly, but in
extreme cases it would be better if each pair of extremities were measured.
It is especially important to see how short people sustain injuries in
crashes, since they of necessity are positioned closer to the
steering-wheel and dashboard than people of normal or tall stature.

In a collaboration with the medical services and insurance companiesand/or
the car industry, the dummy could be the common denominator./.