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Passenger comfort — an overview
The ergonomics of passenger comfort For some time the Scientific Editors of Applied Ergonomics have felt that it would be valuable to readers to provide a group of papers on a common subject in a single issue or successive issues of the Journal. The Scientific Editors invite comments from readers on the desirability of presenting papers in this way from time to time, and welcome suggestions on topics 'which they would like to see covered. At the moment it is planned to publish a series of papers concerning inspection in the next Volume which will appear in 1979. The present Special Issue is wholly devoted to the subject of The Ergonomics of Passenger Comfort, and has been edited by Dr D.J. Oborne of the Psychology Department at the University College of Swansea. The Scientific Editors are grateful to him for undertaking this arduous task so competently and hope that readers find the papers as interesting, stimulating and useful as they do. N.S. Kirk and E.N. Corlett Joint Scientific Editors
Applied Ergonomics Applied Ergonomics 1978, 9.3, 131-136
Passenger comfort
An overview
D.J. Oborne Psychology Department, University College of Swansea
In transport it is axiomatic that passenger comfort is extremely important. This paper considers the concept of comfort and its relationship to the passenger's other travel experiences. The papers which follow in this special issue are then introduced and briefly discussed. The paper concludes with a section which considers factors in the transport environment likely to influence comfort but which have not been covered elsewhere in this issue. These factors include: temperature, ventilation, illumination, photic stimulation, pressure changes on the ear, journey length and task impairment.
Introduction Writing just before the Second World War, W.H. Boulton (1931) said about transport: "From the beginning of life to the very end it attends upon us, and ministers to our necessities and our pleasures. Almost as soon as thought commences to stir within us we realise that some sort of transport is moving us from place to place, it may be a perambulator or our nurse's a r m s . . . When all thought has ceased transport still performs its services toward us, and conveys us to our last resting place." He further argued that: "Human existence as we know it today, in such a land as Great Britain, would be an impossible thing without it, and the British Isles would be an impossible home for
0003-6870/78/030131-06 $02.00 O IPC Business Press
the millions they now sustain, if the service of transport were suddenly withdrawn." It is safe to say that present day transport plays an even more significant part in our lives and its importance will probably increase. Man is constantly on the move, travelling from place to place for a multitude of reasons - to visit a friend, to transact business, to attend the dentist, or perhaps merely to find a place in the sun. Whatever the motivation for travel, the carriage of this special type of 'freight' must be effected in the most efficient manner and in the most pleasant surroundings possible. If the passenger becomes grossly dissatisfied with his journey he may well take his custom elsewhere. The situation, therefore, is a classic ergonomics question of attempting to fit the transport environment to the passenger.
Applied Ergonomics September 1978
131
The aim of this special issue is to draw together papers by experts who have examined by experiment and survey some of the variables which influence the comfort and satisfaction of the passenger. The papers present the reader with a consideration of the important aspects of the ergonomics of passenger comfort, and a summary of the important findings. By way of introduction the present paper attempts to give a definition of comfort, particularly one applicable to passengers. It goes on to outline briefly the contents of the other papers in this special issue and concludes with a highly condensed review of some factors, not fully covered elsewhere in the issue, which are likely to affect passenger comfort.
The concept of comfort Comfort is a subjective concept which is difficult to define and measure. For example, Branton (1972) suggests that, like health, the only appropriate definition of comfort is in terms of its absence, thus arguing that it is possible only to measure varying degrees of discomfort. Nevertheless, some investigators have tried to measure degrees of positive comfort (see, for example, Oborne, 1978). Whether the designer's philosophy is to attempt to reduce discomfort to minimum levels or to induce a positive feeling of comfort, the outcome of his attempts should be the same - namely the production of some sort of optimal state for his passenger. The appropriate definition (and thus means of measurement) of comfort, therefore, lies in the successful definition of such an optimum state. The concepts of comfort (and thus the definitions of the optimum state) advanced by various investigators have been discussed in a previous paper (Oborne, 1978). In essence they would appear to suggest that the designer's aim should be to attempt to produce a total environment which does
not intrude into the passenger's awareness. I'his, of course, is a more difficult task than may appear at first sight since aspects of the environment may not act independently of each other. For example, an attenuation of the noise level may make the vehicular motion more apparent. In addition to his comfort, consideration should also be given to the passenger's satisfaction. This is a term which is certainly broader than comfort in its meaning and which may be more useful in a practical sense, since it implies gratification and payment of debt (The Oxford Dictionary). It suggests, therefore, a state of equity and (of importance to transport operators) perhaps a willingness to return. Richards et al show, in the following paper in this issue, that 'satisfaction' is strongly related to 'comfort'. If the passenger is satisfied with his journey then the negative aspects of it such as cost of ticket, and organisational difficulties, problems with luggage and fatigue are offset by the transport's positive aspects such as comfort and organisational successes. If this is the case, other aspects being equal, there should be no reason for him to look for a different type of transport system for his future use.
Passenger comfort Although the separate papers included in this special issue may at first sight imply the contrary, the degree to which the passenger expresses satisfaction with his chosen mode of transport will depend upon his total experience both past and present. For analysis purposes, any journey may be divided into various stages. A clear distinction may be made between the main stage of the journey, which may or may not involve different forms of transport, and several subsidiary stages both prior to and subsequent to the main stage. For the overall comfort experienced throughout the journey from start to destination, Mayr (1959)has coined the term 'travelling comfort' which, he considers, is composed of three subfactors: Riding comfort, Local comfort and Organisational comfort. Riding comfort is that experienced within the vehicle itself, and represents the primary interest of the present issue. To illustrate the interrelationship of factors within the vehicle environment which contribute to passenger comfort, Mayr produced a 'circle of riding comfort' (see Fig. 1). In doing so, he included not only subjective factors but also technical/structural and physiological/psychological ones. From the discussion of the concept of comfort above, however, it is clear that the ability of the passenger to carry out tasks such as reading and writing has been omitted from Mayr's scheme, although it might be considered to lay at the boundary of "interplay of physiological functions" and "psychical attitude". Local comfort is that experienced at stations, airports and interchange points. It includes experience of short, dependable and comfortable transfers, clear signs and good waiting rooms. Organisational comfort includes factors of an organisational origin such as good connections, and acceptable frequency and reliability of service.
Fig. 1
Mayr's circle of riding comfort (1959)
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A desirable level of comfort is likely also to depend upon the passenger's subjective trade-off between the journey time, the journey cost, the reason for the journey, and the passenger's expectation of the journey comfort.
Thus, passengers embarking on a 10 h journey are likely to require a higher level of comfort, or lower degree of discomfort, than one which is expected to last for 10 min; a journey for which the passenger has bought a first class ticket should be more comfortable than one made in a military vehicle over rough terrain; other things being equal, a journey taking the passenger on holiday may be seen as more comfortable than one which is expected to lead to a difficult interview.
The structure of the special issue The papers to follow are intended to emphasise and elucidate aspects of Mayr's riding comfort analysis. The authors have been selected as experts who are able to discuss different aspects of the problem as they occur in different vehicles. Richards et al consider the comfort of aircraft passengers. Levis is concerned with passengers travelling by bus. Bryan et al discuss noise at it affects passengers in cars and lorries. Reason investigates the specific response of motion sickness experienced in vehicles such as boats. The primary aim of this special issue, therefore, is to present the reader with an exposition of some of the more fundamental problems associated with the ergonomics of the passenger environment. To this end, the first paper by Richards et al is extremely important since it emphasises the role of the passenger in determining his own level of comfort and satisfaction. The authors argue that demographic and individual passenger variables are important determinants of comfort, in addition to passenger attitude and activity. Levis describes some of the extensive work which has been carried out by the Human Factors Group of British Leyland Truck & Bus to investigate ergonomic aspects of the bus environment. In his paper he confines himself to a consideration of the work as it applies to the seated bus passenger - access to the seat, the design of the seat, and dynamic aspects of sitting behaviour. [For a further discussion of the behaviour of the seated passenger and a description of a useful technique for measuring 'seat comfort', the interested reader is referred to Branton and Grayson (1967). A further consideration for the seated passenger, of course, is what he should do with his luggage. The interested reader is referred to Williams (1977) who describes a study, undertaken whilst he was with British Rail, to investigate the problems experienced by passengers with accompanied luggage.] The following three papers (Bryan et al; Oborne; Reason) consider primary aspects of the vehicle which may affect passenger comfort and satisfaction. Bryan et al discuss the extensive research which they have carried out concerning the noise experienced inside motor care. On the basis of earlier published work, they tentatively suggest noise criteria and suggest directions for future research. [For further information on the theme of vehicle noise and the passenger, the reader is referred to Eade and Hardy (1977) who discuss noise levels in a rail vehicle and summarise the basis on which suitable specifications for the interior noise levels in a new vehidle may be selected.] In their paper Bryan et al show that car passengers generally rated the vehicle noise as being quieter than did laboratory subjects who were presented with the same noise types and levels. A similar picture may be observed in Jacobsen et al's paper at the end of this issue. Reviewing studies of the
relationship between vehicle vibration and passenger comfort, Obome investigated the relation between the results of field and laboratory trials. He shows that, although laboratory studies will not predict passenger reaction precisely in the field, any discrepancy will tend to err on the side of reducing vibration levels below those required by the passenger. It would appear to be safe, therefore, for a designer to use results from properly controlled laboratory studies. Reason, too, considers the effect of motion. He pays attention to low frequency motion, which may well give rise to motion sickness. He argues that motion sickness is a normal reaction to a mismatch between incoming sensory information (the sensory rearrangement theory) and discusses means by which "nauseogenic symptoms" may be reduced. Each of the papers so far discussed have considered primarily one aspect of the vehicle environment at a time: space, noise, vibration and motion. In the final paper, Jacobsen et al present data which draw together the effects of a number of physical factors acting simultaneously to produce composite models of human reaction to vehicle environments.
Other factors Apart from that of Richards et al, the subsequent papers in this special issue deal with what Hawkins (1973) has termed primary comfort factors, ie, those factors which are of relevance at the stage of basic vehicle design. It is obvious, however, that these are not the only factors important to comfort and satisfaction. Nor are they, in some cases, the most important considerations. Secondary environmental factors such as lighting and heating, which become relevant at the stage of interior design, and marginal factors such as responses to visual phenomena and pressure changes, are also important. As Jacobsen et al illustrate in the final paper in this issue, the passenger will integrate all aspects of his environment to produce a comfort response. The integration will include considerations of the extent to which the environment impinges on various aspects of passenger performance. The integration also includes the reason for the journey, the length of the journey, the passenger's past experiences, his expectations, his attitudes, and the sex of the passenger. An issue concerning passenger comfort would not be complete, therefore, if some of these secondary, marginal and integration factors were not discussed in slightly more detail.
Temperature Response to the thermal environment is extremely complex, with a number of different variables being involved. Fanger (1970), for example, suggests that the maintenance of thermal comfort over a period of time depends upon the existence of heat balance, the primary variables of which are: The internal heat production per unit body surface area Thermal resistance of the clothing Air temperature Mean radiant temperature Pressure of water vapour in the ambient air Relative air velocity Mean skin temperature Heat loss per unit body surface area by evaporation of sweat.
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133
Since some of these factors (eg, clothing type and degree of passenger sweating) are outside the control of the designer, and since some will remain relatively static in a closed transport environment, eg, air velocity or passenger work rate, the primary variables of interest to the design engineer will be air temperature and humidity. These have been used by the American Society of Heating, Refrigeration, and Air Conditioning Engineers Inc (ASHRAE) to produce a comfort chart (1966). Chapter 8 of the Applied Ergonomics Handbook (1970) provides useful discussion of the importance of the various factors involved in the thermal environment, in addition to a summary of their measurement and control.
Ventilation Intimately related to the question of providing adequate heating is that of providing good ventilation. The condition of the air inside a vehicle is most important for the maintenance of passenger well-being by the provision of a continuous supply of oxygen and the removal of odours. The ASHRAE standard 55--66 (1966) suggests that "air m o t i o n . . , should not exceed 45 ft/min [0.23m/s] and shall not be less than 10 ft/min [0"06 m/s] at any time". McFarland (1969) provides further suggestions: "Very low rates of air movement will produce a feeling of stuffiness, and body odours and tobacco smoke may become very irritatintg. Optimally 35 to 40 ft s/min [0.0165 - 0-0188 m~/s] of fresh air should be supplied per individual at velocities of between 20 and 60 ft/min [0.1 -- 0.3 m/s] in order to maintain a sense of freshness without creating undesirable drafts. It should be remembered that increased air velocities tend to h~ve a greater cooling effect which may be advantageous in summer but uncomfortable in winter".
lllumination A consideration of the illumination level within a vehicle is important (Hawkins, 1973)for three reasons, safety, convenience and comfort. First, in relation to safety, the illumination of passenger circulation areas such as gangways and entrances and exits needs to be adequate for the perception of thresholds and changes in floor level as well as of obstructions and important notices. Secondly, in relation to convenience, passengers will, for example, require more illumination if they wish to read or write. Thirdly, in relation to comfort, it is necessary to minimise glare. Glare may result from two sources, externally from the sun and internally from badly positioned lights. Whatever the cause, the result might range from mild discomfort and annoyance to, perhaps, an impediment to vision and a reduction in safety (Hopkinson, 1972). Flicker can be an additional source of discomfort and annoyance. Many discharge lamps exhibit a 50 Hz variation in light output, and this may be perceived as flicker by substantial numbers of people. The design of an overall lighting installation which can adequately provide for each of these separate criteria is, inevitably, a complex process and beyond the scope of this short review. However, Hopkinson and Collins (1970) cover the important areas involved in the ergonomics of lighting,
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and the Illuminating Engineering Society (II'_S)has produced a code for interior lighting (1977).
Marginal factors These factors appear important primarily in high speed transportation and include both visual disturbance and problems due to pressure changes. The first type of visual problem is that of photic stimulation giving rise to 'flicker vertigo' (Carstens and Kresge, 1965). This is caused by the interruption of light at fast and regular intervals by objects such as telegraph poles and wires. Certain frequencies and intensities of light stimulation may produce vertigo, convulsions or loss of consciousness, but less serious effects are feelings of dizziness and nausea, nervousness, or simply a vague feeling of unease. The critical frequency band appears to be 9 15 flashes per second, although studies by Johnson (1963)produced 'uncomfortable' and 'distracting' responses over the wider frequency range of 2 20 flashes/s. A second problem is that of train nystagmus, which is also known as photokinetic nystagmus and optical rotary nystagmus. This " o c c u r s . . . when successive moving objects (in relationship to the eyes) excite attention as they traverse the visual field. The eyes follow one object in a (relatively) slow movement towards the periphery and then jerk back quickly when they are attracted by its successor" (DukeElder, 1949). The optimum stimulus for its production is a succession of objects passing at a rate of 3 12 per second, although it is observed at frequencies below and above this band. The associated symptoms consist primarily of dizziness and nausea, with a marked individual variation in the incidence of symptoms (Carstens and Kresge, 1965). The pressure change problems occur in high speed transportation as a result of sudden pressure changes inside the vehicle as it passes into and out of tunnels. The primary site for the perception of such pressure changes appears to be in the ear and it appears that if such changes can be held to 0.06 lb/in 2 (0.4 k Pa) or less, then the level of discomfort should be broadly acceptable. Passengers with heavy colds however, would still experience discomfort (McFarland, 1969). A further problem of this type might also arise as the vehicle passes buildings adjacent to it, although Carstens and Kresge (1965)argue that the vehicle interior pressure changes under these circumstances may prove to be insignificant. The effect of journey length on passenger comfort It would not be unreasonable to suppose that a passenger's reaction to a vehicle will depend, to some extent, upon the length of time for which he is exposed to the journey. Over a relatively short period of time, reaction may change as a result of adaptation, whereas for journeys of longer periods, fatigue and accompanying discomfort may occur. The result of the relatively few studies carried out to investigate this variable, however, do not support this contention. For example, the author has presented rating scales to passengers travelling by train (representing a journey length of up to 2½ h) and by cross channel hovercraft (representing a journey length of up to 20 rain). Passengers in each case were asked separately to rate the intensity of the vibration experienced (on a scale "rough k smooth") and their overall assessment of comfort ("very comfortable very uncomfortable"). Relating the responses to the
Table 1: Correlations (7") between passenger ratings and the length of their journey
Rating
Train
Hovercraft
Vibration intensity
-0.02
-0.02
0.01
-0-06
Overall comfort
to the papers which follow and constitute this special issue. Passenger comfort is a subject which, with the introduction of new and faster forms of transport, has become extremely important. As Richards et al show in the next paper, only when we are comfortable are we satisfied. As most transport operators realise, only when we are satisfied will we become good fare-paying passengers.
References passengers' journey length produced no significant correlations American Society of Heating, Refrigeration and Air (see Table 1). Supporting evidence for such data may be seen in a study carried out by Griffin and Whitham (1976). Their results indicated that the levels of discomfort produced by a 16 Hz vibration stimulus at 0.75 m/s 2 RMS remained constant throughout a 36 rain period. The effects of task impairment on passenger comfort A number of authors have argued that when vehicle features intrude into the passenger's awareness to such an extent that he is unable to carry out tasks such as reading or writing, then frustration and annoyance will increase and his overall assessment of comfort will be reduced. Unfortunately, no studies may be found which have investigated this aspect, although Richards et al do touch on the subject in their paper which follows. The most which may be said is that under more extreme conditions all environmental features affect task performance. Consequently people are likely generally to become frustrated and annoyed if they are unable to do what they wish. As an example of performance reduction caused by environmental factors it has been shown that vibration, because it affects the body structure, degrades the efficient completion of motor tasks such as writing or eating. Gray et al (1976) exposed seated laboratory subjects to 3 h of 5 Hz vertical vibration at 1.2 m/s 2 During this time, they were asked at specific periods to carry out a writing task. The quality of the transcript was later assessed by a school teacher using a 0 - 1 0 scale (very good - illegible). Their results indicated that vibration clearly impaired handwriting. Vibration may also affect visual tasks such as reading. Blurring of the visual image on the retina, due to the relative movement between the eye and viewed object, seems to be the most apparent cause of problems. At frequencies around 15-18 Hz, the eyeball itself may resonate (Lange and Coermann, 1962). Griffin and Lewis (1978) and Lewis and Griffin (1978) have recently reviewed the effects of vibration on vision and on manual control Noise is another stressor commonly experienced in a vehicle environment. As Bryan et al point out later in this issue, it may interfere with communication, making it difficult to hear instructions or conversation. In addition, noise has been shown to have an effect on mental and other tasks. The results, however, are inconclusive, with some experiments showing a decrement in performance, others an increase, and still others no change. The personality and sex of the subjects chosen appear to be important variables (Hockey, 1972).
Conditioning Engineers
1966 Thermal Comfort Conditions. ASHRAE Standard 55-66; NY.
Applied Ergonomics Handbook 1970 Applied Ergonomics, 1,210-216. Thermal Comfort in Industry.
Boulton, W.H. 1931 The Pageant of Transport Through the Ages. London: Sampson Low, Marston.
Branton, P. 1972 Ergonomic Research Contributions to the Design of the Passenger Environment. Paper presented to a Passenger Environment Conference sponsored by the Institution of Mechanical Engineers, London, March.
Branton, P., and Grayson, G. 1967 Ergonomics, 10, 35-51. An evaluation of train seats by observation of sitting behaviour. Carstens, J.P., and Kresge, D. 1965 Literature survey of pasenger comfort limitations of high speed ground transports. United Aircraft Research Laboratories, Report D - 910353 - 1.
Duke-Elder, S. 1949 A textbook of ophthalmology. St Louis: C.U. Mosby Co.
Earle, P.W., and Hardy, E.J. 1977 JSound Vib, 51,403-415. Railway vehicle internal noise.
Fanger, P.O. 1970 Thermal Comfort: Analysis and applications in environmental engineering. New York. McGraw-Hill. Gray, R., Wilkinson, R.T., Maslen, K.R., and Rowlands, G.F. 1976 The effects of 3 hours vertical vibration at 5 Hz on the performance of some tasks. RAE Technical Report 76011. Griffin, M.J., and Lewis, C.H. 1978 JSound Vib, 56, 383-413. A review of the effect of vibration on visual acuity and continuous manual control. Part I: Visual Acuity.
Griffin, M.J., and Whitham, E.M. 1976 JSound Vib, 48, 333-339. Duration of whole-body vibration exposure: Its effects on comfort. Hawkins, N.M. 1973 Passenger comfort limitations on the design of high speed transportation systems. Department of Transport Technology Report, Loughborough University, TT 7309.
Conclusions
Hockey, G.R.J.
The aim of this paper has been to define comfort, particularly passenger comfort, and to provide an introduction
1972 JSound Vib, 20, 299-304. Effects of noise on human efficiency and some individual differences.
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Hopkinson, R.G. 1972 Applied Ergonomics, 3, 206-215. Glare from daylight in buildings.
Lewis, C.H., and Griffin, M.J. 1978 JSound Vib, 56,415-457. A review of the effects or" vibration on visual acuity and continuous manual control. Part lI: Continuous manual control.
Hopkinson, R.G., and Collins, J.B.
Mayr, R. 1959 The Railway Gazette, 9 October, 266--269. Comfort in railway travel.
1970 The ergonomics of lighting. London: MacDonald Technical & Scientific. IES 1977 Code for interior lighting. Illumination Engineering Society, London.
Johnson, L.C. 1963 Aerospace Medicine, 34, 49-63. Flicker as a helicopter pilot problem.
Lange, K.O., and Coermann, R.R. 1972 Human Factors, 4, 291-300. Visual acuity under vibration.
McFarland, R.A. 1969 Human factors in ground transportation with special reference to passenger comfort and safety. Paper presented to High Speed Ground Transportation Conference, Carnegie-Mellon University. Obome, D.J. 1978 Applied Ergonomics, 9, 45-49. Techniques available for the assessment of passenger comfort. Williams, J.C. 1977 Applied Ergonomics, 8, 151 - 157. Passenger accompanied luggage.
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Applied Ergonomics September 1978
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Applied Ergonomics Applied Ergonomics 1978, 9.3, 131-136
Passenger comfort
An overview
D.J. Oborne Psychology Department, University College of Swansea
In transport it is axiomatic that passenger comfort is extremely important. This paper considers the concept of comfort and its relationship to the passenger's other travel experiences. The papers which follow in this special issue are then introduced and briefly discussed. The paper concludes with a section which considers factors in the transport environment likely to influence comfort but which have not been covered elsewhere in this issue. These factors include: temperature, ventilation, illumination, photic stimulation, pressure changes on the ear, journey length and task impairment.
Introduction Writing just before the Second World War, W.H. Boulton (1931) said about transport: "From the beginning of life to the very end it attends upon us, and ministers to our necessities and our pleasures. Almost as soon as thought commences to stir within us we realise that some sort of transport is moving us from place to place, it may be a perambulator or our nurse's a r m s . . . When all thought has ceased transport still performs its services toward us, and conveys us to our last resting place." He further argued that: "Human existence as we know it today, in such a land as Great Britain, would be an impossible thing without it, and the British Isles would be an impossible home for
0003-6870/78/030131-06 $02.00 O IPC Business Press
the millions they now sustain, if the service of transport were suddenly withdrawn." It is safe to say that present day transport plays an even more significant part in our lives and its importance will probably increase. Man is constantly on the move, travelling from place to place for a multitude of reasons - to visit a friend, to transact business, to attend the dentist, or perhaps merely to find a place in the sun. Whatever the motivation for travel, the carriage of this special type of 'freight' must be effected in the most efficient manner and in the most pleasant surroundings possible. If the passenger becomes grossly dissatisfied with his journey he may well take his custom elsewhere. The situation, therefore, is a classic ergonomics question of attempting to fit the transport environment to the passenger.
Applied Ergonomics September 1978
131
The aim of this special issue is to draw together papers by experts who have examined by experiment and survey some of the variables which influence the comfort and satisfaction of the passenger. The papers present the reader with a consideration of the important aspects of the ergonomics of passenger comfort, and a summary of the important findings. By way of introduction the present paper attempts to give a definition of comfort, particularly one applicable to passengers. It goes on to outline briefly the contents of the other papers in this special issue and concludes with a highly condensed review of some factors, not fully covered elsewhere in the issue, which are likely to affect passenger comfort.
The concept of comfort Comfort is a subjective concept which is difficult to define and measure. For example, Branton (1972) suggests that, like health, the only appropriate definition of comfort is in terms of its absence, thus arguing that it is possible only to measure varying degrees of discomfort. Nevertheless, some investigators have tried to measure degrees of positive comfort (see, for example, Oborne, 1978). Whether the designer's philosophy is to attempt to reduce discomfort to minimum levels or to induce a positive feeling of comfort, the outcome of his attempts should be the same - namely the production of some sort of optimal state for his passenger. The appropriate definition (and thus means of measurement) of comfort, therefore, lies in the successful definition of such an optimum state. The concepts of comfort (and thus the definitions of the optimum state) advanced by various investigators have been discussed in a previous paper (Oborne, 1978). In essence they would appear to suggest that the designer's aim should be to attempt to produce a total environment which does
not intrude into the passenger's awareness. I'his, of course, is a more difficult task than may appear at first sight since aspects of the environment may not act independently of each other. For example, an attenuation of the noise level may make the vehicular motion more apparent. In addition to his comfort, consideration should also be given to the passenger's satisfaction. This is a term which is certainly broader than comfort in its meaning and which may be more useful in a practical sense, since it implies gratification and payment of debt (The Oxford Dictionary). It suggests, therefore, a state of equity and (of importance to transport operators) perhaps a willingness to return. Richards et al show, in the following paper in this issue, that 'satisfaction' is strongly related to 'comfort'. If the passenger is satisfied with his journey then the negative aspects of it such as cost of ticket, and organisational difficulties, problems with luggage and fatigue are offset by the transport's positive aspects such as comfort and organisational successes. If this is the case, other aspects being equal, there should be no reason for him to look for a different type of transport system for his future use.
Passenger comfort Although the separate papers included in this special issue may at first sight imply the contrary, the degree to which the passenger expresses satisfaction with his chosen mode of transport will depend upon his total experience both past and present. For analysis purposes, any journey may be divided into various stages. A clear distinction may be made between the main stage of the journey, which may or may not involve different forms of transport, and several subsidiary stages both prior to and subsequent to the main stage. For the overall comfort experienced throughout the journey from start to destination, Mayr (1959)has coined the term 'travelling comfort' which, he considers, is composed of three subfactors: Riding comfort, Local comfort and Organisational comfort. Riding comfort is that experienced within the vehicle itself, and represents the primary interest of the present issue. To illustrate the interrelationship of factors within the vehicle environment which contribute to passenger comfort, Mayr produced a 'circle of riding comfort' (see Fig. 1). In doing so, he included not only subjective factors but also technical/structural and physiological/psychological ones. From the discussion of the concept of comfort above, however, it is clear that the ability of the passenger to carry out tasks such as reading and writing has been omitted from Mayr's scheme, although it might be considered to lay at the boundary of "interplay of physiological functions" and "psychical attitude". Local comfort is that experienced at stations, airports and interchange points. It includes experience of short, dependable and comfortable transfers, clear signs and good waiting rooms. Organisational comfort includes factors of an organisational origin such as good connections, and acceptable frequency and reliability of service.
Fig. 1
Mayr's circle of riding comfort (1959)
132
AppliedErgonomics September 1978
A desirable level of comfort is likely also to depend upon the passenger's subjective trade-off between the journey time, the journey cost, the reason for the journey, and the passenger's expectation of the journey comfort.
Thus, passengers embarking on a 10 h journey are likely to require a higher level of comfort, or lower degree of discomfort, than one which is expected to last for 10 min; a journey for which the passenger has bought a first class ticket should be more comfortable than one made in a military vehicle over rough terrain; other things being equal, a journey taking the passenger on holiday may be seen as more comfortable than one which is expected to lead to a difficult interview.
The structure of the special issue The papers to follow are intended to emphasise and elucidate aspects of Mayr's riding comfort analysis. The authors have been selected as experts who are able to discuss different aspects of the problem as they occur in different vehicles. Richards et al consider the comfort of aircraft passengers. Levis is concerned with passengers travelling by bus. Bryan et al discuss noise at it affects passengers in cars and lorries. Reason investigates the specific response of motion sickness experienced in vehicles such as boats. The primary aim of this special issue, therefore, is to present the reader with an exposition of some of the more fundamental problems associated with the ergonomics of the passenger environment. To this end, the first paper by Richards et al is extremely important since it emphasises the role of the passenger in determining his own level of comfort and satisfaction. The authors argue that demographic and individual passenger variables are important determinants of comfort, in addition to passenger attitude and activity. Levis describes some of the extensive work which has been carried out by the Human Factors Group of British Leyland Truck & Bus to investigate ergonomic aspects of the bus environment. In his paper he confines himself to a consideration of the work as it applies to the seated bus passenger - access to the seat, the design of the seat, and dynamic aspects of sitting behaviour. [For a further discussion of the behaviour of the seated passenger and a description of a useful technique for measuring 'seat comfort', the interested reader is referred to Branton and Grayson (1967). A further consideration for the seated passenger, of course, is what he should do with his luggage. The interested reader is referred to Williams (1977) who describes a study, undertaken whilst he was with British Rail, to investigate the problems experienced by passengers with accompanied luggage.] The following three papers (Bryan et al; Oborne; Reason) consider primary aspects of the vehicle which may affect passenger comfort and satisfaction. Bryan et al discuss the extensive research which they have carried out concerning the noise experienced inside motor care. On the basis of earlier published work, they tentatively suggest noise criteria and suggest directions for future research. [For further information on the theme of vehicle noise and the passenger, the reader is referred to Eade and Hardy (1977) who discuss noise levels in a rail vehicle and summarise the basis on which suitable specifications for the interior noise levels in a new vehidle may be selected.] In their paper Bryan et al show that car passengers generally rated the vehicle noise as being quieter than did laboratory subjects who were presented with the same noise types and levels. A similar picture may be observed in Jacobsen et al's paper at the end of this issue. Reviewing studies of the
relationship between vehicle vibration and passenger comfort, Obome investigated the relation between the results of field and laboratory trials. He shows that, although laboratory studies will not predict passenger reaction precisely in the field, any discrepancy will tend to err on the side of reducing vibration levels below those required by the passenger. It would appear to be safe, therefore, for a designer to use results from properly controlled laboratory studies. Reason, too, considers the effect of motion. He pays attention to low frequency motion, which may well give rise to motion sickness. He argues that motion sickness is a normal reaction to a mismatch between incoming sensory information (the sensory rearrangement theory) and discusses means by which "nauseogenic symptoms" may be reduced. Each of the papers so far discussed have considered primarily one aspect of the vehicle environment at a time: space, noise, vibration and motion. In the final paper, Jacobsen et al present data which draw together the effects of a number of physical factors acting simultaneously to produce composite models of human reaction to vehicle environments.
Other factors Apart from that of Richards et al, the subsequent papers in this special issue deal with what Hawkins (1973) has termed primary comfort factors, ie, those factors which are of relevance at the stage of basic vehicle design. It is obvious, however, that these are not the only factors important to comfort and satisfaction. Nor are they, in some cases, the most important considerations. Secondary environmental factors such as lighting and heating, which become relevant at the stage of interior design, and marginal factors such as responses to visual phenomena and pressure changes, are also important. As Jacobsen et al illustrate in the final paper in this issue, the passenger will integrate all aspects of his environment to produce a comfort response. The integration will include considerations of the extent to which the environment impinges on various aspects of passenger performance. The integration also includes the reason for the journey, the length of the journey, the passenger's past experiences, his expectations, his attitudes, and the sex of the passenger. An issue concerning passenger comfort would not be complete, therefore, if some of these secondary, marginal and integration factors were not discussed in slightly more detail.
Temperature Response to the thermal environment is extremely complex, with a number of different variables being involved. Fanger (1970), for example, suggests that the maintenance of thermal comfort over a period of time depends upon the existence of heat balance, the primary variables of which are: The internal heat production per unit body surface area Thermal resistance of the clothing Air temperature Mean radiant temperature Pressure of water vapour in the ambient air Relative air velocity Mean skin temperature Heat loss per unit body surface area by evaporation of sweat.
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Since some of these factors (eg, clothing type and degree of passenger sweating) are outside the control of the designer, and since some will remain relatively static in a closed transport environment, eg, air velocity or passenger work rate, the primary variables of interest to the design engineer will be air temperature and humidity. These have been used by the American Society of Heating, Refrigeration, and Air Conditioning Engineers Inc (ASHRAE) to produce a comfort chart (1966). Chapter 8 of the Applied Ergonomics Handbook (1970) provides useful discussion of the importance of the various factors involved in the thermal environment, in addition to a summary of their measurement and control.
Ventilation Intimately related to the question of providing adequate heating is that of providing good ventilation. The condition of the air inside a vehicle is most important for the maintenance of passenger well-being by the provision of a continuous supply of oxygen and the removal of odours. The ASHRAE standard 55--66 (1966) suggests that "air m o t i o n . . , should not exceed 45 ft/min [0.23m/s] and shall not be less than 10 ft/min [0"06 m/s] at any time". McFarland (1969) provides further suggestions: "Very low rates of air movement will produce a feeling of stuffiness, and body odours and tobacco smoke may become very irritatintg. Optimally 35 to 40 ft s/min [0.0165 - 0-0188 m~/s] of fresh air should be supplied per individual at velocities of between 20 and 60 ft/min [0.1 -- 0.3 m/s] in order to maintain a sense of freshness without creating undesirable drafts. It should be remembered that increased air velocities tend to h~ve a greater cooling effect which may be advantageous in summer but uncomfortable in winter".
lllumination A consideration of the illumination level within a vehicle is important (Hawkins, 1973)for three reasons, safety, convenience and comfort. First, in relation to safety, the illumination of passenger circulation areas such as gangways and entrances and exits needs to be adequate for the perception of thresholds and changes in floor level as well as of obstructions and important notices. Secondly, in relation to convenience, passengers will, for example, require more illumination if they wish to read or write. Thirdly, in relation to comfort, it is necessary to minimise glare. Glare may result from two sources, externally from the sun and internally from badly positioned lights. Whatever the cause, the result might range from mild discomfort and annoyance to, perhaps, an impediment to vision and a reduction in safety (Hopkinson, 1972). Flicker can be an additional source of discomfort and annoyance. Many discharge lamps exhibit a 50 Hz variation in light output, and this may be perceived as flicker by substantial numbers of people. The design of an overall lighting installation which can adequately provide for each of these separate criteria is, inevitably, a complex process and beyond the scope of this short review. However, Hopkinson and Collins (1970) cover the important areas involved in the ergonomics of lighting,
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and the Illuminating Engineering Society (II'_S)has produced a code for interior lighting (1977).
Marginal factors These factors appear important primarily in high speed transportation and include both visual disturbance and problems due to pressure changes. The first type of visual problem is that of photic stimulation giving rise to 'flicker vertigo' (Carstens and Kresge, 1965). This is caused by the interruption of light at fast and regular intervals by objects such as telegraph poles and wires. Certain frequencies and intensities of light stimulation may produce vertigo, convulsions or loss of consciousness, but less serious effects are feelings of dizziness and nausea, nervousness, or simply a vague feeling of unease. The critical frequency band appears to be 9 15 flashes per second, although studies by Johnson (1963)produced 'uncomfortable' and 'distracting' responses over the wider frequency range of 2 20 flashes/s. A second problem is that of train nystagmus, which is also known as photokinetic nystagmus and optical rotary nystagmus. This " o c c u r s . . . when successive moving objects (in relationship to the eyes) excite attention as they traverse the visual field. The eyes follow one object in a (relatively) slow movement towards the periphery and then jerk back quickly when they are attracted by its successor" (DukeElder, 1949). The optimum stimulus for its production is a succession of objects passing at a rate of 3 12 per second, although it is observed at frequencies below and above this band. The associated symptoms consist primarily of dizziness and nausea, with a marked individual variation in the incidence of symptoms (Carstens and Kresge, 1965). The pressure change problems occur in high speed transportation as a result of sudden pressure changes inside the vehicle as it passes into and out of tunnels. The primary site for the perception of such pressure changes appears to be in the ear and it appears that if such changes can be held to 0.06 lb/in 2 (0.4 k Pa) or less, then the level of discomfort should be broadly acceptable. Passengers with heavy colds however, would still experience discomfort (McFarland, 1969). A further problem of this type might also arise as the vehicle passes buildings adjacent to it, although Carstens and Kresge (1965)argue that the vehicle interior pressure changes under these circumstances may prove to be insignificant. The effect of journey length on passenger comfort It would not be unreasonable to suppose that a passenger's reaction to a vehicle will depend, to some extent, upon the length of time for which he is exposed to the journey. Over a relatively short period of time, reaction may change as a result of adaptation, whereas for journeys of longer periods, fatigue and accompanying discomfort may occur. The result of the relatively few studies carried out to investigate this variable, however, do not support this contention. For example, the author has presented rating scales to passengers travelling by train (representing a journey length of up to 2½ h) and by cross channel hovercraft (representing a journey length of up to 20 rain). Passengers in each case were asked separately to rate the intensity of the vibration experienced (on a scale "rough k smooth") and their overall assessment of comfort ("very comfortable very uncomfortable"). Relating the responses to the
Table 1: Correlations (7") between passenger ratings and the length of their journey
Rating
Train
Hovercraft
Vibration intensity
-0.02
-0.02
0.01
-0-06
Overall comfort
to the papers which follow and constitute this special issue. Passenger comfort is a subject which, with the introduction of new and faster forms of transport, has become extremely important. As Richards et al show in the next paper, only when we are comfortable are we satisfied. As most transport operators realise, only when we are satisfied will we become good fare-paying passengers.
References passengers' journey length produced no significant correlations American Society of Heating, Refrigeration and Air (see Table 1). Supporting evidence for such data may be seen in a study carried out by Griffin and Whitham (1976). Their results indicated that the levels of discomfort produced by a 16 Hz vibration stimulus at 0.75 m/s 2 RMS remained constant throughout a 36 rain period. The effects of task impairment on passenger comfort A number of authors have argued that when vehicle features intrude into the passenger's awareness to such an extent that he is unable to carry out tasks such as reading or writing, then frustration and annoyance will increase and his overall assessment of comfort will be reduced. Unfortunately, no studies may be found which have investigated this aspect, although Richards et al do touch on the subject in their paper which follows. The most which may be said is that under more extreme conditions all environmental features affect task performance. Consequently people are likely generally to become frustrated and annoyed if they are unable to do what they wish. As an example of performance reduction caused by environmental factors it has been shown that vibration, because it affects the body structure, degrades the efficient completion of motor tasks such as writing or eating. Gray et al (1976) exposed seated laboratory subjects to 3 h of 5 Hz vertical vibration at 1.2 m/s 2 During this time, they were asked at specific periods to carry out a writing task. The quality of the transcript was later assessed by a school teacher using a 0 - 1 0 scale (very good - illegible). Their results indicated that vibration clearly impaired handwriting. Vibration may also affect visual tasks such as reading. Blurring of the visual image on the retina, due to the relative movement between the eye and viewed object, seems to be the most apparent cause of problems. At frequencies around 15-18 Hz, the eyeball itself may resonate (Lange and Coermann, 1962). Griffin and Lewis (1978) and Lewis and Griffin (1978) have recently reviewed the effects of vibration on vision and on manual control Noise is another stressor commonly experienced in a vehicle environment. As Bryan et al point out later in this issue, it may interfere with communication, making it difficult to hear instructions or conversation. In addition, noise has been shown to have an effect on mental and other tasks. The results, however, are inconclusive, with some experiments showing a decrement in performance, others an increase, and still others no change. The personality and sex of the subjects chosen appear to be important variables (Hockey, 1972).
Conditioning Engineers
1966 Thermal Comfort Conditions. ASHRAE Standard 55-66; NY.
Applied Ergonomics Handbook 1970 Applied Ergonomics, 1,210-216. Thermal Comfort in Industry.
Boulton, W.H. 1931 The Pageant of Transport Through the Ages. London: Sampson Low, Marston.
Branton, P. 1972 Ergonomic Research Contributions to the Design of the Passenger Environment. Paper presented to a Passenger Environment Conference sponsored by the Institution of Mechanical Engineers, London, March.
Branton, P., and Grayson, G. 1967 Ergonomics, 10, 35-51. An evaluation of train seats by observation of sitting behaviour. Carstens, J.P., and Kresge, D. 1965 Literature survey of pasenger comfort limitations of high speed ground transports. United Aircraft Research Laboratories, Report D - 910353 - 1.
Duke-Elder, S. 1949 A textbook of ophthalmology. St Louis: C.U. Mosby Co.
Earle, P.W., and Hardy, E.J. 1977 JSound Vib, 51,403-415. Railway vehicle internal noise.
Fanger, P.O. 1970 Thermal Comfort: Analysis and applications in environmental engineering. New York. McGraw-Hill. Gray, R., Wilkinson, R.T., Maslen, K.R., and Rowlands, G.F. 1976 The effects of 3 hours vertical vibration at 5 Hz on the performance of some tasks. RAE Technical Report 76011. Griffin, M.J., and Lewis, C.H. 1978 JSound Vib, 56, 383-413. A review of the effect of vibration on visual acuity and continuous manual control. Part I: Visual Acuity.
Griffin, M.J., and Whitham, E.M. 1976 JSound Vib, 48, 333-339. Duration of whole-body vibration exposure: Its effects on comfort. Hawkins, N.M. 1973 Passenger comfort limitations on the design of high speed transportation systems. Department of Transport Technology Report, Loughborough University, TT 7309.
Conclusions
Hockey, G.R.J.
The aim of this paper has been to define comfort, particularly passenger comfort, and to provide an introduction
1972 JSound Vib, 20, 299-304. Effects of noise on human efficiency and some individual differences.
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Hopkinson, R.G. 1972 Applied Ergonomics, 3, 206-215. Glare from daylight in buildings.
Lewis, C.H., and Griffin, M.J. 1978 JSound Vib, 56,415-457. A review of the effects or" vibration on visual acuity and continuous manual control. Part lI: Continuous manual control.
Hopkinson, R.G., and Collins, J.B.
Mayr, R. 1959 The Railway Gazette, 9 October, 266--269. Comfort in railway travel.
1970 The ergonomics of lighting. London: MacDonald Technical & Scientific. IES 1977 Code for interior lighting. Illumination Engineering Society, London.
Johnson, L.C. 1963 Aerospace Medicine, 34, 49-63. Flicker as a helicopter pilot problem.
Lange, K.O., and Coermann, R.R. 1972 Human Factors, 4, 291-300. Visual acuity under vibration.
McFarland, R.A. 1969 Human factors in ground transportation with special reference to passenger comfort and safety. Paper presented to High Speed Ground Transportation Conference, Carnegie-Mellon University. Obome, D.J. 1978 Applied Ergonomics, 9, 45-49. Techniques available for the assessment of passenger comfort. Williams, J.C. 1977 Applied Ergonomics, 8, 151 - 157. Passenger accompanied luggage.
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