RESEARCH Commercial Vehicles

18 ATZ worldwide 9/2002 Volume 104

Coaches are considered to be a well-established means oftransport for moving persons over short to long distances. As along-haul means of transport, coaches, with their 10 % marketshare, rank even higher than trains. Whereas the comfort of thepassengers is discussed relatively often, the workstation of thedriver is rarely the subject of scientific investigation. In theresearch project “Fahrerarbeitsplatz im Reisebus” (driver work-station in coaches), University of Applied Science Hamburgcarried out a statistical study of the working conditions of thecoach driver and, in this article, formulated rules for theergonomic design of the workstation.

By Wolfgang Kraus

Der Fahrerarbeitsplatz

im Reisebus

You will find the figures mentioned in this article in the German issue of ATZ 9/2002 beginning on page 792.

The Driver Workstationin Coaches

19ATZ worldwide 9/2002 Volume 104

1 Introduction

Coaches are a well-established modern

means of transport [1]. They can be used for

many different purposes, from long-haul

trips to cultural journeys and excursions. As

a long-haul means of transport, coaches,

with their 10 % market share, rank even

higher than trains [2]. Drivers play a key

role in the safety of passengers and other

road users. A comfortable and ergonomic

workstation is therefore an absolute neces-

sity for sound driving performance on the

part of the coach drivers.

It is an uncontested fact that coach dri-

vers suffer special stresses, caused,

amongst other things, by traffic conditions,

the environment, passengers and the vehi-

cle itself. In the light of the above, the

Berufsgenossenschaft für Fahrzeug-haltun-

gen (BGF), the Bundesverband Deutscher

Omnibusunternehmer (bdo) and the Ge-

werkschaft Öffentliche Dienste, Transport

und Verkehr (ver.di/ötv) initiated a re-

search project at the University of Applied

Science in Hamburg to demonstrate the

key aspects of these stresses in a prelimi-

nary and a main study and derive recom-

mendations concerning the design of the

coach driver's workstation from the results

of these studies.

2 Preliminary Study

In the preliminary study [2] of the research

project, the ergonomics of the vehicles sold

on the market were reviewed and deficits

and optimization potentials pointed out. A

number of defects were first determined by

interviewing coach drivers. Amongst other

things, 31 % of coach drivers said they were

unable to sit in a relaxed posture while

driving. After a longer trip, 49 % of drivers

suffer from physical complaints. These sub-

jective assessments were confirmed by

analysis of driver postures in vehicles.

Detailed information about illness-relat-

ed absenteeism among coach drivers is not

available in Germany at present. According

to statistics of the Bundesverband der Be-

triebskrankenkassen (BKK), members of

the transport sector and, in particular, peo-

ple working in passenger transport suffer

most frequently from one of the illnesses

listed below according to frequency [2]:

1. Diseases of the respiratory system

2. Diseases of the muscoskeletal system

and connective tissue

3. Diseases of the digestive organs

4. Injuries and poisoning.

In the passenger transport sector, the

number of people who are unfit for work

due to diseases of the muscoskeletal system

is clearly above the average for all sectors:

■ Average across all sectors of industry:

22.3 %

■ Insured persons in the passenger trans-

port sector: 32.4 %

Changes in work organization and im-

provements in the traffic situation are diffi-

cult to realize. Major improvements and

changes in the work situation can thus only

be achieved by optimizing the driver's

workstation. This is the target of the main

study.

3 Main Study

Proceeding from the deficits determined in

the preliminary study, the main study fo-

cused primarily on the design of the dri-

ver's workstation in terms of ergonomic

and human-engineering findings. The

main study, including a presentation of all

results, was conducted at the Hamburg

University of Applied Sciences. Reference to

the methodology of driver-workstation op-

timization seems important in this context.

The objectives of this research project are as

follows:

■ To determine characteristic maps of er-

gonomic design that can be used as the ba-

sis for the design of driver workstations in

coaches

■ To preserve the manufacturers' freedom

to design individual solutions in accor-

dance with ergonomic criteria; and thus

■ To avoid detailed design instructions for

components such as control panel, seat,

pedals, steering wheel and other controls.

This approach makes the research pro-

ject very different from the VDV project on

the design of driver workstations in public

service buses, which defines the compo-

nents and their arrangement in the specifi-

cations. In the author's opinion, laying

down rigid requirements and component

definitions in a regulation may impede

competition between companies to devel-

op new, improved solutions.

The main study focuses on describing

minimum ergonomic requirements and de-

sign-characteristic maps that can be ap-

plied to various vehicles. The study aims at

providing recommendations and deliber-

ately avoids the character of standards and

regulations.

3.1 Analysis Using the RamsisCAE ModelRamsis, the CAE model that is widely used

in the automotive industry, was also used

in this research project. In terms of upright

sitting postures, normal in commercial ve-

hicles, open questions regarding posture

adjustment and comfort evaluation arose

during project processing. To calibrate the

CAE model, the driver's workstation of a

coach model from one manufacturer was

computer-analyzed by way of an example.

The objective was to compare the results of

the computer analysis with the postures

determined in the preliminary study on the

basis of a specific work example. The sitting

postures calculated by the computer corre-

sponded to a large extent to the unfavor-

able values determined in practice, Figure 1.

The influence of the exposure period, i. e.

changes in sitting posture during long trips,

could not be simulated in the CAE model.

Generally, the values obtained with the

CAE model tend to be better. From the large

number of different sitting posture adjust-

ments, the CAE model tends to select the

better solution and constantly strives to ar-

rive at an optimum result. In the light of

the above, the research project always com-

pared the comfort statements of the CAE

model with the comfort values to be found

in the literature.

3.2 AnthropometricsWorkstations in commercial vehicles are

nowadays designed on the basis of anthro-

pometrical data from the total population.

Sample measurements and data collated

by transport services, however, point to

job-related anthropometrics. Vehicle manu-

facturers have extensive experience in this

field and emphasize that very few of these

vehicles are driven by women. This fact is

important and affects in particular seat ad-

justment range, steering wheel position

and visibility.

The research project raised the question

of job-related changes in body measure-

ments resulting from factors such as nutri-

tion and lack of physical activity. Social and

psychological parameters also play a role in

the choice of career and may prove to be

distinguishing factors as compared with

the total population. This discussion, which

took place in the course of processing of the

main study resulted in the proposal to sub-

ject this specific occupational group to an-

thropometrical measurements. The anthro-

pometrical measurements were analyzed

in a separate project by the research group

of industrial anthropology of Kiel Universi-

ty [3]. The anthropometrical results were

incorporated into the research project of

Hamburg and used as a basis for generat-

ing a coach-driver population for the pur-

pose of CAD representation.

3.3 Definition of Coach-DriverPopulationA measurement study on truck and coach

drivers commissioned by the BGF demon-

strated clear differences to the total popula-

tion, thus justifying the definition of a sep-

arate population for this research project

RESEARCH Commercial Vehicles

20 ATZ worldwide 9/2002 Volume 104

[3]. Male and female coach and truck dri-

vers were measured throughout Germany.

The results are summarized below:

■ In this occupational group women are

clearly underrepresented

■ Bus drivers are shorter than the total

population; but their arms, feet, hands and

fingers are the same size as those of the to-

tal population

■ On the whole, bus drivers weigh consid-

erably more than the total population

■ Comparatively speaking, bus drivers

have considerably higher trunk dimension

values and thus wider shoulders, elbows,

and buttocks and a greater abdominal body

depth

■ Comparatively speaking, bus drivers

tend to have relatively longer bodies and

shorter legs (causing them to look large

when seated).

In the analysis, a 0.5 % change in physi-

cal features or acceleration for the respec-

tive body measurement is assumed and

taken into account [3]. The newly defined

population allows for the small share of

women in this occupational group and

their anthropometrical data. Additionally,

a Dutch study, carried out by the TNO Hu-

man Factors Research Institute, is taken

into consideration in this research project.

The Dutch study describes the especially

high acceleration values among young per-

sons. In the study, this type is referred to as

P99 (99 percent, i.e. only 1 % of the popula-

tion is larger) and represents, as required in

practice, the group of young people of

above-average height, Figure 2.

Table 1 presents the anthropometrical

body height and weight data of the select-

ed population derived from the study. In

the CAE model Ramsis, these anthropomet-

rical data are represented in corresponding

Ramsis type series. In this context, minor

differences between the measured anthro-

pometrical data and the CAE model occur

when the data is transferred to the comput-

er. These differences are within the toler-

ance range and can thus be neglected.

3.4 Seated Posture ModelThe seated posture primarily involves static

exertions, which leads to muscular fatigue

in the long term. Generally, this posture is

regarded as unphysiological, i. e. unnatural.

Work conducted in this posture can thus

only be carried out for limited periods.

An optimum sitting posture thus only

describes a relatively favorable body pos-

ture generated by physiologically known

angles between trunk, head and limbs. An-

gle ranges that can be maintained by dri-

vers for lengthy periods and are found to be

relatively comfortable are referred to as

“comfort angles”.

The preliminary study provided a de-

tailed description of existing body postures

of coach drivers and reveals considerable

ergonomic deficits. The clearly visible ten-

dency towards kyphosis is influenced in

particular by the positioning of the steering

wheel. This posture causes different pres-

sures and overpressures in the interverte-

bral discs. Since there are no sensors

(nerves), the drivers do not feel any pain

and are thus not made aware of their un-

natural posture. In the long term, this pos-

ture may harm the driver's spine and loco-

motor system [2]. After driving for more

than two hours, harmful changes in body

posture become clearly evident. The upper

part of the body leans forward in a slump.

The natural spinal posture of a standing

person is characterized by lumbar lordosis,

thorax kyphosis and cervical vertebral lor-

dosis. The preliminary study refers to ex-

aminations by Nachemson and Andersson,

who guarantee even distribution of the

load acting on the spine and high elasticity

and shock absorption in this posture. The

orthopedic requirements for the seated

posture are derived from there. Thus, the

position of the vertebral column of a sitting

person should correspond to that of a

standing person.

The lordosis position demanded from an

orthopedic point of view must thus be sup-

ported by seat design. To prevent kyphosis

of the pelvis, the center of gravity of the up-

per part of the body should be behind the

ischial tuberosity. This requires the upper

part of the body to tilt slightly backwards, a

design criterion called the torso tilt in pack-

age design plans.

The seated posture model in this re-

search project describes the basic posture of

the generated population arranged in an

orthopedically correct position. This is the

starting point for all geometrical defini-

tions. The basic postures of the selected per-

sons and their assignment to driver-work-

station geometry are effected via the accel-

erator position in standard driving. The per-

sons' point of reference to the pedal surface

is the ball-toe point, also called ball-pres-

sure point.

The basic adjustment of body postures

in the CAE model Ramsis is generated via

the view to a vehicle that is driving ahead.

For the purposes of this research project,

the view to a passenger car driving 40 m

ahead is set and sitting posture calculated

from this. The eyes of the generated per-

sons are focused on the brake lights of the

passenger car. At a speed of 80 km/h, this

corresponds to half the distance between

bus and passenger car, Figure 3.

The back incline of the seated person is a

measure widely used for body posture ad-

justment in the automotive industry. In

line with the values recommended in er-

gonomic literature, a back incline of 15° is

defined for upright sitting. In cases involv-

ing steep visual angles to the front and

downwards, the 15° back incline allows

comfortable neck angles. This is an impor-

tant condition for fatigue-free driving. The

shoulder and neck region should be ex-

posed to as little stress as possible and re-

quire little muscular effort to maintain the

desired head posture.

The seated posture model [4] is the basis

for defining the minimum dimensions of

driver workstations, Figure 4. To ensure

that the results are also suitable for steer-

ing-wheel and seat positioning, comfort

measurements were carried out in a sitting

box and a survey was conducted. The inves-

tigations were carried out with a selected

population corresponding to the group of

coach drivers, Figure 5.

3.5 Layout Scheme for theControl ElementsThe models for the layout of control ele-

ments described in the literature can only

be applied to the “driver workstation in

coaches” model to a limited extent. The

known methods do not include any docu-

mented anthropometrical definitions with

respect to the reachability of controls. In

this research project, the priorities regard-

ing the reachability of controls are linked to

anthropometrical dimension strategies,

thus allowing their layout to be reviewed

without their exact geometric position hav-

ing to be rigidly defined. The priorities with

respect to the reachability of controls are

described in the form of anthropometrical

envelope curves.

The same procedure is applied to the

visibility of control elements. The priorities

for visibility are oriented to the ranges of

visual angles known in the literature. Dif-

ferentiations are defined according to eye

and face fields including ergonomic angle

ranges.

3.5.1 Categories of Control ElementsThe categories “central control elements”

and “other control elements” were recom-

mended for the driver workstation in

coaches in order to take safety and the spe-

cial importance of certain controls into ac-

count. Central control elements are those

which directly affect safety when the vehi-

cle is being driven and with which the dri-

ver is in constant contact. These compo-

nents are subject to special evaluation and

are designed according to very narrowly

defined ergonomic requirements. Regard-

less of the recommendations concerning

RESEARCH Commercial Vehicles

21ATZ worldwide 9/2002 Volume 104

reachability and visibility, separate er-

gonomic recommendations are developed.

The values derived for location and position

result from the seated-posture model de-

veloped. Central controls are:

■ Steering wheel

■ Control stalks

■ Pedals.

With regard to the reachability of steer-

ing wheel and control stalks, the degrees of

freedom defined for the movement ranges

are small. As far as shoulder movements

are concerned, anthropometrical anteposi-

tions of the shoulders are not permitted.

The steering-wheel position is determined

using a method known from automotive

design and development.

For the “other control elements”, the pri-

orities concerning their positions, locations

and reachability will be defined after com-

pletion of the evaluation of a comprehen-

sive survey conducted amongst coach dri-

vers. Other controls mainly include knobs,

switches, gear-shift lever and similar con-

trols. The structure of control element lay-

out in a driver workstation in coaches is de-

termined according to the following crite-

ria:

■ Visibility and reachability

■ Formation of logical groups

■ Position and location.

3.5.2 Definitions Regarding Visibility and ReachabilityIn the defining of visibility and reachabili-

ty, three priorities must be considered:

■ Priority I: optimum visual range (visible);

can be reached with optimum comfort

from a sitting position (reachable)

■ Priority II: range for accurate viewing

(visible); can be reached with maximum

length from a sitting position (reachable)

■ Priority III: periphery of the visual field

(visible); reachable from a sitting position

only by a change in posture (reachable).

3.5.3 Definitions for FormingLogical GroupsThe recommendation of grouping and logi-

cally structuring the control elements

seems wise in view of the large number of

functions. In this case, these functions are

to be structured according to their func-

tions:

■ Driving

■ Illumination

■ Heating - ventilation – air-conditioning

■ Communications.

3.5.4 Definition of Position andLocationHere, the positions of the control elements

(on the control panel) are defined in line

with a rough spatial structure in a total of

six control panels A to F, e. g. front left, front

center, or front right. The structure facili-

tates rapid spatial orientation on the part of

the driver.

3.6 Envelope Curves of ArmMovementsThe envelope curves of arm movements

were separately analyzed from the point of

view of comfort at the ergonomics labora-

tory of industrial anthropology in Kiel.

They are dimensioned for the upright sit-

ting postures defined in the CAE model and

arranged according to priorities as de-

scribed above. The use of the Ramsis enve-

lope curves of hand-action range to define

reachability is only accepted to a limited

extent. In the study setup, anthropometri-

cally measured persons were asked to de-

termine certain spatial points by means of

exact movement patterns. These move-

ment patterns correspond to three aspects

of comfort with a complex movement

strategy:

■ Priority I: Envelope curve defined by

hand-arm movements including all de-

grees of freedom of the shoulder joint

■ Priority II: Envelope curve defined by

hand-arm movements involving comfort-

able shifts in the upper part of the body, in-

cluding slight rotations, Figure 6

■ Priority III: Here, posture changes from

the sitting position are possible. However,

the body must remain in contact with the

seat.

The priority III should only be assigned

to controls that are almost only operated in

non-critical situations, e.g. when the vehi-

cle is standing. The spatial points deter-

mined were translated into a CAD surface

model and form the basis for the reachabil-

ity of controls in line with priorities I to III,

Figure 7.

In conjunction with the definition ac-

cording to position and location, controls

can now be defined taking their anthropo-

metrical reachability and spatial positions

into account without impeding individual

driver-workstation design possibilities,

Figure 8 and Table 2.

4 Presentation of the Results

The results of the studies are presented in

three parts: firstly the closing report for the

research sponsor, secondly a proposals re-

port [5] which will provide designers active

in the field with concise design recommen-

dations in the form of text and drawings

and thirdly a section containing a CD-ROM

with CAD data including all important

characteristic maps in constructive form.

The computerized analyses were conduct-

ed with CAD software Catia V4.2.2 and the

CAE program Ramsis V3.7. The CAD study

was prepared by Prof. Dipl.-Ing. Stefan Bi-

galke, who teaches at the HAW Hamburg.

The data record includes all relevant er-

gonomic characteristic maps for the P5 fe-

male bus driver, the P95 male bus driver

and the P99 standard population.

5 Implementation of theResults

After initial presentations, the results of the

main study met with a positive echo from

manufacturers. For this reason, some of the

manufacturers will quickly implement the

ergonomic characteristic maps in vehicles,

Figure 9. The BGF will present this research

project at its booth B07 in hall 27 at the IAA

Commercial Vehicles 2002 in Hanover, Ger-

many. Additionally, activities have been

initiated to include the driver workstation

as defined in the main study in a future EC

coach and bus regulation.

References

[1] Kraus, W.; Koos, H.; Lippmann, R.: Ergonomis-che Fahrerplatzanalyse bei MAN: eine Vergle-ichsstudie mit realen und virtuellen Menschen.ATZ 99 (1997), Nr. 3, S. 156–161

[2] N. N.: Fahrerarbeitsplatz im Reisebus. Berichtzur Vorstudie. 2. Auflage, Institut für Arbeits-wissenschaft der RWTH Aachen, Institut fürKraftfahrwesen (ika) der RWTH Aachen, Beruf-sgenossenschaftliches Institut für Arbeits-sicherheit (BIA), Aachen 1998

[3] Helbig, K.; Küchmeister, G.: Anthropometri-sche und biomechanische Untersuchungen anFahrern und Fahrerinnen von Reisebussen undLastkraftwagen.ProjektberichtdesForschungs-projekts, nicht veröffentlicht, HAW Hamburg,Fachbereich Fahrzeugtechnik und Flugzeug-bau, 2000

[4] N.N.: Fahrerarbeitsplatz im Reisebus. Haupt-studie des Forschungsprojekts, HAW Ham-burg, Fachbereich Fahrzeugtechnik undFlugzeugbau, Oktober 2001

[5] N.N.: Fahrerarbeitsplatz im Reisebus. Emp-fehlungen zur ergonomischen Gestaltung.HAW Hamburg, Fachbereich Fahrzeugtechnikund Flugzeugbau, Oktober 2001

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