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Downloaded from SAE International by Istanbul Teknik Universitesi, Friday, August 25, 2017

PREPRINT: Subject to revision. Permission to publish this paper, in full or in
part, after its presentation and with credit
to the author and the Society may be ob­
tained upon request. The Society is not re­
sponsible for statements or opinions advanced in pa­
pers or discussions at its Meetings.

295A

6/6/%3

LIBRARY

P A S S E N G E R R I D I N G C O M F O R T C R I T E R I A AND
M E T H O D S O F A N A L Y S I N G R I D E AND V I B R A T I O N

,

DATA

By
PROF. EL H. C. A. vanELDIKTHIEME
Vehicle Research Laboratory
TECHNOLOGICAL UNIVERSITY
Delft, Holland

For presentation at the
1961 SAE INTERNATIONAL CONGRESS
AND EXPOSITION OF AUTOMOTIVE ENGINEERING
Cobo Hall, Detroit, Michigan
January 9-13, 1961

Written discussion of this paper will be accepted by SAE until M a r c h

.1, 1961.

Three double-spaced copies a r e appreciated.

Discussion is printed if paper is published in SAE Transactions.
SOCIETY of AUTOMOTIVE ENGINEERS,lhei, 485 Lexington Avenue,New York 17, KT. Y.

Downloaded from SAE International by Istanbul Teknik Universitesi, Friday, August 25, 2017

PASSENGER RIDING COMFORT CRITERIA AND METHODS OF
ANALYSING RIDE AND VIBRATION DATA

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SUMMARY
Because the ride comfort problem is a very complex problem,
as a general feeling of well-being in a vehicle, only one
aspect will be discussed in the paper, namely that of the
mechanical vibrations in a frequency region of 0.1 - 100 cps.
The objective method of physiological and performance tests
will be briefly related, but more attention will be paid to
the subjective research methods, where a person gives his
own sensation opinion. On the basis of the studies of human
tolerance to vibrations, a number of comfort criteria is dis­
cussed.
With the aid of these criteria results have been achieved in
the examination of acceleration records and tapes with modern
high-speed level analysers and computing equipment.
Although the goal to establish a relationship between an "over­
all" comfort index and purchase price of passenger cars and
buses today remains still unsolved (if ever possible to achieve),
an attempt has been made to show the way to evaluate only the
ride comfort index of different car makes, which can be com­
pared to the price classes.
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INTRODUCTION
The ride comfort problem, as a general feeling of well-being in a vehi­
cle, is very complex. Many factors and variables are involved, such as heating
and ventilation, a feeling of safety in different traffic, and weather conditions,
noise, and suspension characteristics. Also, steering, braking, and acceleration
must be taken into account as general riding of the vehicle.
Considering the above from a wider point of view, traveling comfort may
be regarded as the sum of all measures which maintain and improve the well-being
of a person and reduce his fatigue.
Traveling comfort (l)* consists of riding comfort, which is the comfort
experienced in the road or rail vehicle itself, while local comfort is the comfort
experienced at stations, interchange points, and airports, and comprises comfort­
able transfer, waiting rooms, refreshment facilities, and clear signs. Another
group of factors which has a considerable effect on traveling comfort, such as

TTumbers in parentheses designate References at end of paper.

Downloaded from SAE International by Istanbul Teknik Universitesi, Friday, August 25, 2017

- 2 good connections, frequency of service, reliability independent of weather and
climate, and custom clearance may be regarded as organizational comfort.
The desirable level of comfort for road and rail vehicles will depend
on the journey time, because a journey of 10 hr from one city to another will re­
quire a higher level of riding comfort than a ride of only 10 min.
It is the purpose of this paper to consider riding comfort, and then
only the mechanical vibration problem in a frequency region of 0.1 - 100 cps.
Therefore, the equally important acoustical frequency range from 20 - 20,000 cps
will not be dealt with.
COMFORT CRITERIA OBTAINED FROM OBJECTIVE
AND SUBJECTIVE TESTS
OBJECTIVE TESTS (2) - In these medical tests of bodily conditions, dis­
comfort and fatigue are assumed to be synonymous terms, and, therefore, the human
fatigue is considered to be a criterion of vehicle riding.
Physiological Tests - Fatigue has been investigated by Moss by physio­
logical tests, such as measurements of blood pressure, of the amount of oxygen
inhaled per unit of time, of the carbon-dioxide combining power of the blood, of
the quantity of blood sugar, heart rate and the use of electrocardiograms, esti­
mates of the number of white or red blood cells per unit volume of blood, and
so on.
The object of these tests; to give a quantitative measure of fatigue
related to vehicle riding, appeared to be very difficult. The recovery effect
over a long period of driving is well known, also known is that many of the gen­
eral physiological functions are not measurably altered until the state of ex­
haustion is approached. These tests also can be influenced by the emotional
state and condition of health of the subject.
Performance Tests - Since the physiological tests of riding fatigue
proved on the whole unsatisfactory, Moss made an extensive study of performance
tests. Because the degree of skill would increase up to a certain point with
practice, Moss tried to determine this normal level for each subject. Therefore,
he investigated fatigue with subjects having a stabilized level of skill, by per­
formance tests such as the steadiness of hand, the number-checking efficiency,
speed of reaction, sensitivity of the skin to touch, and sensitivity of the eye
to light intensity. The loss of bodily equilibrium appeared to be a reliable
test.
Verbal Reports - The verbal reports on riding fatigue give the subject's
opinion as to his impressions of dizziness, sleepiness, nervousness, headache,
nausea, stiffness of muscles, and other symptoms.
It appears very difficult to attach precise significance to the physio­
logical and performance tests without the corroboration of the verbal reports.
The fatigue level required here as an indication of a criterion of vehicle riding
seems uncertain, because a very limited amount of correlation has been established
between fatigue and vibration characteristics of the vehicle.

Downloaded from SAE International by Istanbul Teknik Universitesi, Friday, August 25, 2017

- 3Fatigue is not only a question of the total suspension system, and it
is well known that a number of other factors also contribute to fatigue, such as
noise, traffic density, weather conditions, and forces required to work pedals
or steering.
Due to all these difficulties, the study of comfort has been carried
out almost exclusively on the basis of subjective tests, and here a reasonably
good correlation has been established between comfort criteria and vibration char­
acteristics of the vehicle.
SUBJECTIVE TESTS - The purpose of these tests is to study the influence
on the human subject of vibrations of various kinds, and also to gain basic data
with reference to traffic and industrial vibrations.
All pertinent data available on comfort as a subjective concept have
been established by asking a person whether he feels comfortable or not when sub­
jected to harmonic vibrations. These data are usually given in terms of vibration
amplitude versus frequency, and sometimes as acceleration amplitude versus fre­
quency.
Reiher-Meister Criteria - Well known, as the first of the more thorough
researches, is the German work carried out by Reiher and Meister at Stuttgart,
(1931) and the later work (3) of Meister (1935)• They used a platform which could
be vibrated either horizontally or vertically. The noise in the test room was re­
duced to a minimum. A total of 25 persons, of ages varying from 20 to kO years,
were subjected to the tests. The subjects stood or lay on the vibrating platform,
and, when they were lying down, the platform was vibrated horizontally in the di­
rection of the axis of the body and at right angles to it.
After being exposed to one type of vibration for only 15 min, the test
persons were asked to classify the vibrations experienced into one of the six
main zones, 0-5?
0 = Imperceptible, not noticeable
1 = Barely perceptible, Just noticeable
2 = Distinctly perceptible, not uncomfortable
3 = Slightly disagreeable, not pleasant
h = Disagreeable, annoying
5 = Exceedingly disagreeable, unbearable.
Only the results of the vibration sensitivity of standing persons are
here reproduced (Fig. l), but npw in terms of acceleration amplitude versus fre­
quency, instead of the amplitude frequency curves originally given. This is done
because, in using the chart in practice, we have, as a rule, the easily measured
acceleration amplitude available.
Jacklin-Liddell Criteria - Further tests to determine the discomfort
due to automobile riding were carried out by Jacklin (k) and Liddell of Purdue
University. They also observed the reactions of humans to vibration when sitting
on a controlled vibrating seat or platform, and in moving vehicles. The subjec­
tive states which the individual experienced were classified by Jacklin .as

Downloaded from SAE International by Istanbul Teknik Universitesi, Friday, August 25, 2017

- k perceptible, disturbing, and uncomfortable. Below the "perceptible" point, the
subject is not conscious of moving; at the "disturbing" point, one feels the ne­
cessity for exerting some muscular effort to keep all parts of the body moving
in unison with the seat; while at the "uncomfortable" point, the person wants
very little of the treatment (Fig. 2 ) .
The main results of these tests carried out with passengers seated on
hard seats can be represented by the equation

K = Ae°> 6f
where:

K

=

Constant, called comfort index

A

=

Maximum acceleration, ft/sec2

e

=

Basis of .natumL logarithm (2.7183)

f

=

Frequency of vibration, cps

For cushioned seats, Jacklto (h) gives a number of other comfort formu­
lae for passengers subjected to vertical, longitudinal, or transverse vibrations.
When dealing with both vertical and horizontal vibration, the maximum
"Kc" value is given by the vector sum
Kc

« \/Kr2

+ K ] 2 + Kt 2

Janeway Recommended Limits - On the basis of a study of available data,
the SAE Riding Comfort Research Committee published in 1950 a set of reference
charts as a second edition of Ride and Vibration Data (5)- In agreement with the
later Meister thresholds of 1935 and of other investigators, we find in these SAE
ride and vibration data recommended limits given by R. N. Janeway for vertical
sinusoidal vibrations (Fig. 3)»
The curves of the various comfort zone limits can be represented by the
equation
c
where;

= af*

a = Amplitude, in.
f

=

Frequency, cps

x

=

Exponent varying from 1; to 3

With x - 1, the comfort zone limit or passenger sensitivity depends on
af = c; that is, it is proportional to the vibration velocity, while with x = 2,
the sensitivity depends upon acceleration. With x;= ,3* the sensitivity depends
upon the rate of change of the acceleration values-

Downloaded from SAE International by Istanbul Teknik Universitesi, Friday, August 25, 2017

The Janeway limits in the low-frequency range of 1-6 cps are af3 = 2
with a maximum "ye1^1" value of 40 ft/sec3. In the 6-20 cps range, we find
af2 s 1/3 with a maximum acceleration not more than 3-3$ gj while in the highfrequency range of 20-60 cps the value af = l/60 with a maximum velocity limit
of O.IO5 in./sec.
Sperling Criteria - It might be of some interest to members of SAE to
report about the research work carried out on the Continent and particularly
about the assessment of railcar riding, because it is quite possible that this
work is more or less unknown to SAE automobile engineers.
With the object of ascertaining the effect of vibration upon passengers
as experienced in railway service, Helberg and Sperling (6) carried out a largescale test in 19^1, by recording the reactions of some 25 employees of the Rolling
Stock Test Dept. of the Reichsbahn at Berlin- Grunewald, when subjected to sinu­
soidal vibrations. Only people with some experience with regard to riding quali­
ties of vehicles were used as test subjects, since their reactions were considered
to be more reliable. After tests from 2 to 10 min they assessed the discomfort
they experienced.
As a basis for the evaluation of the riding quality, the expression
ca3f5 was considered, which consequently represents the product of work done and
yerk:
a2

(2rtf)2 . a (2nf)3 = ca3f5

The actual comfort index, as far as the individual is concerned, is pre­
sented by the equation:

Wz
where:

-

2.7

\ / a-3f? =

0.896

a

= Amplitude, mm

f

=

A

= Acceleration amplitude, cm/sec^

Frequency, cps

In 1956, Sperling (7) introduced a corrective factor into this formula,
in order to take human reactions more closely into account. The corrected formula
is:
Wz

=

2.7

\y

a3f5 . F (f)

In Fig. k, the variation of the original comfprt index, W z , has been
shown as a function of the frequency and the acceleration in in./sec2, and in Fig.
5, the correction factor F(f) and N ^ F ( f ) as a function of the frequency, sepa­
rately for the horizontal and vertical vibrations. From Fig. k, it can be seen
that the comfort index, W z = 1, means a very good riding quality, while ¥ z = 3»5
is barely satisfactory.

Downloaded from SAE International by Istanbul Teknik Universitesi, Friday, August 25, 2017

-6 But the riding quality of a railcoach is not uniform over a long dis­
tance, even if the speed remains constant. Varying amplitudes and frequencies
are encountered in rapid succession, and, therefore, it is necessary to determine
a mean value, W * , as the ride factor.

L
w

where:

lj_, ±2
Wz,, W z

zzm

2"Z2

+

1

3Wz3

1-. + -L« -f" 1 « +

...»

= Lengths of different part sections of the testrun
= Representing comfort indices

With this formula, the worst riding qualities, even over only a very
short section of the testrun, determine predominantly the general ride factor
value, W z , due to the factor W z 10.
In fact, the riding of a railcoach must be classified as poor, if it is
bad only 10$ or less of the journey, even if it is Very good for the remainder.
The method established proved suitable for passenger coaches as well as for goods
wagons.
Mauzin-Sperling Criteria - Due to the establishment of the Office de
Recherches et d'Essais (O.R.E.) in Holland, a branch of the Union Internationale
des Chemins de Per (U.I.C.), the French Railway scientific worker Mauzin was
brought closer together than before with Dr. Ing.', Sperling of the Deutsche
Bundesbahn. They compared their test results obtained on moving platforms and
on riding in vehicles of most variable types, and found there was a reasonable
agreement. It was agreed to average their results and the mean curves obtained,
reproduced in Figs. 6-8, formed the basis of a new method (8).
It is interesting to see (Fig. 6) that vertical accelerations \J2. times
greater than lateral accelerations (Fig. 7) of the same frequency have the same
comfort value.
With the aid of these curves of equal comfort and of equal fatigue, it
is possible to convert 'acceleration data, obtained from a record of carriage rid­
ing, into' the amount of time after which an average passenger in a coach will ex­
perience a sense of fatigue. As an example for lateral accelerations, the values
obtained from Fig. 8 are shown in Table11.
Mauzin and Sperling have suggested that the riding of a carriage is
considered adequate by the average passenger when the fatigue time corresponds
to a period T of 6 hr. The quality on a ride of a goods wagon may be regarded
as adequate, if the period T is ^5 min.
Under varying conditions, but constant speed, the average overall fa­
tigue time T is determined as follows:

Downloaded from SAE International by Istanbul Teknik Universitesi, Friday, August 25, 2017

-7 T

=
T

where;

l

T

2

T

3

ti, t2 •. °.. = Duration of time of the measurements during which fatigue
times T-J_, f 2 • • • • • were noted

Since the testruns are made at constant speed, the values ti, t2 .. • are
proportional to the lengths lj, I2 .....
Sperling (7) gave Table 2 as an indication of the values of his comfort
index, W z , versus fatigue time, T.
The general case of establishing the fatigue time of accelerations of
varying magnitudes, which occur at numerous frequencies, will here, due to its
necessary length, not be described.
The possibly interested reader will find typical results, obtained with
a detailed working of an example, in literature (8) of this new method of assessing
the riding of vehicles in fatigue time. One remark about this method is to be mades
namely, to analyse a great number of long test records, the time involved is very
great indeed, being a serious disadvantage of the method recently published.
Dieckmann Criteria - Other test results, due to Dr. Dieckmann (9) of the
German Max-Planck Institute of Dortmund, are also of interest.
Dieckmann, in agreement with R. Coermann (2), considered the human body
as a very complicated vibrating structure. Of course, studying this presents great
difficulties, because the elasticity constants of the individual materials such as
bones and muscles vary to a great extent, and the muscular tension is also a con­
stantly changing factor, contributing appreciably to the total elasticity of the
body. The whole acts as a complicated damped resilient mass system, having slight­
ly varying natural frequencies and damping factors.
It was found, when a person is subjected to vibrations of a certain fre­
quency, all parts of his body will vibrate with the same frequency, but different
amplitudes. To establish more data on this phenomenon with a vibrating platform,
Dieckmann fixed accelerometers on the standing test person's head, shoulder, and
hip. When taking the acceleration amplitude of the platform at 100$, it can be
seen from the results (Fig. 9) that at the lower frequencies, head and hip vibrate
almost the same as the platform. In the frequency range of 4-5 cps, a vibration
amplification is noted, although the amplification of the head with respect to the
platform is less than the amplification of the shoulder or the hip.
In the higher frequency range, the acceleration amplitudes of head,
shoulder, and hip are less than the platform amplitude. At frequencies in excess
of 120 cps, nearly all vibrations are damped out by the body.
When taking the shoulder vibration to be 100$, comparison with the head
vibration (Fig. 10) shows a very high acceleration amplitude of the head, with re­
spect to the amplitude of the shoulder at 20-30 cps.

Downloaded from SAE International by Istanbul Teknik Universitesi, Friday, August 25, 2017

-8 Similar curves were found when the test persons were sitting on the vi- .
brating platform. The observed phenomena are typical natural frequencies of the
human body parts and, therefore, the frequency range of 4-5 cps is an undesirable
zone for human well-being. (See also Fig. 5-)
In his publications (9), Dieekmann published also the results of vibra­
tion tests with persons sitting on hard, spring-cushioned, or foam-rubber seats,
and studied the reactions experienced from vertical as well as horizontal vibra­
tions. He completed his laboratory test on moving platforms with road tests on
a bus.
As a result of his tests, Dieekmann introduced a constant, K, as com­
fort index, where the value of the K-factor indicates the degree of comfort. The
classification of the different comfort zones is shown in Table 3.
For the various frequency ranges, the comfort factor, K, is represented
by the equations;

where:

K

=

af 2

for the frequency range

0 -

K

=

5 af

for the frequency range

5 ~ 40 cps

K

=

200a

for the frequency range 40 - 200 cps

5 cps

a = Amplitude, mm
f

=

Frequency, cps

The comfort values mentioned may be valid for pure sinusoidal vibrations
in buildings, but are not applicable for road and rail vehicle vibrations, because
on normal roads we never have continuously pure sinusoidal motion.
Our Delft laboratory road test results of acceleration measurements on
the seated test person indicated K = 5-7 for a good riding passenger car on an ex­
cellent concrete road. Tests at k-5 mph,with about 20 modern passenger cars on bad
cobblestone roads, produced K-factors varying from 3O-65, but the fatigue time ob­
served was definitely more than 1 min, as suggested originally in the classifica­
tion table of Dieekmann.
Therefore, new different classifications for different groups of vibra­
tions are temporarily given by Dieekmann, namely as maximum values K = 1 for liv­
ing rooms, K = 10 for persons subjected to vibrations (10) of machine foundations,
K = 30 for road vehicles, and K = 100 for "off-the-road" vehicles. But also,
these new values probably will have to be corrected, because a good leafspring
bus on a bad cobblestone road gives K = .94!
Rail Passenger Comfort in Curved Track - So far, the comfort criteria
have been considered on a basis of subjective reactions to vibratory motions.
But there are also other motions of the vehicle, which are largely aperiodic in
nature and irregular in occurrence, such as cornering, braking, and so on.
In relation to cornering, a paper (ll) should be mentioned, published
in 195^ by the Association of American Railroads, prepared by R. Ferguson on
"Passenger Ride Comfort on Curved Track." This report gives the results of tests


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