Project C1 - Train environment simulator for optimising passenger comfort |
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INVESTIGATORS: Professor Mike Griffin (Institute of Sound and Vibration Research, University of Southampton)Professor Ken Parsons (Loughborough University)
RESEARCHER(S): Dr Henrietta Howarth, Martin Toward, Dr Naser Nawayseh (ISVR, University of Southampton)
RESEARCH STUDENTS: Mandy Lo, Judy Joseph (ISVR, University of Southampton)Paul Underwood, Paddy Stennings (Loughborough University)
Industrial Collaborators: AMEC Rail Limited; Interfleet Technology Ltd.; Eurostar; North West Trains
Original objectives: Original objectives as presented in the grant proposal:
- To provide a facility capable of reproducing the internal environment of railway carriages, including noise, vibration and thermal environment
- To conduct fundamental and applied research so as to develop modern guidelines for the comfort and activity disturbance of railway passengers
- To make the simulation facility available for the study of specific questions raised by the industry
Revised objectives: Subsequent to original proposal:The current objectives of the project are the original objectives but with revised timescales. In recognition
of the importance of the facility the University of Southampton decided to install the simulator within a purpose-build laboratory of a new building. This delayed the construction of the simulator but made it possible to improve the specifications. The installation of the simulator commenced in December
2006 and the new building will opened in 2007. Less than one-third of the original costs of the simulator were supported by RRUK, although it was hoped that the EPSRC would assist with additional funding. In the event, the University has funded all the remaining costs of the simulator and its installation as well as the very substantial additional costs of the new laboratory.
Project summary at time of proposal: A simulation facility will be designed and installed to be capable of reproducing the ranges of noise, vibration and thermal conditions of relevance to railway carriages. It will be operated in conjunction with other facilities (including an existing simulator for studying motion sickness and postural stability in tilting trains) in the Human Factors Research Unit The research programme will seek to provide methods of measuring, evaluating and assessing the measured or predicted environment in railway carriages so as to identify passenger reaction (discomfort, interference with activities, motion sickness,
safety) and means of minimising such adverse reactions. Specific projects will include: (i) effects of vibration on passenger operation of keyboard devices, (ii) equivalence between noise, vibration and thermal conditions, (iii) postural stability, and (iv) field studies of comfort in trains. In addition, the research will review and update existing guidelines for comfort in the train environment. The research will provide a body of expertise on all aspects of passenger comfort. The expertise will also extend to knowledge of effects of railway-induced noise and vibration in buildings.
Summary of outcomes: A train environment simulator has been designed and is awaiting installation
to facilitate the accurate reproduction of the acoustic, thermal and vibratory experienced within in a railway carriage. The simulator will allow the study of the effects of the internal environment on passenger comfort within a train. The pioneering motion simulator has been developed in collaboration
with Servotest hydraulic systems. The simulator has the capability to reproduce motions in 6-axes from DC to 50 Hz with very low background vibration (< 0.01 ms-2 r.m.s), low acceleration distortion (< 10%) and cross axis coupling (< 5%). A number of safety systems have been developed and build in to the simulator to ensure the system complies with International Standard BS EN ISO 13090:1998 in any failure condition (International Organization for Standardization, 1998).
A simulator cabin has been developed and constructed for use on the multi-axis simulator. The cabin is designed to fit two facing rows of standard train seats and a table. A virtual acoustic system has been installed within the cabin. The virtual acoustic system allows the playback of signals in such a way that the listener experiences the illusion of being in a ‘virtual’ environment. Binaural recordings can be filtered using cross-talk cancellation filters so that, when played back through the system, the signals that arrive at the listener’s ear are similar to those recorded using a dummy head. Listeners should feel as though they are in the environment in which the dummy head was placed to record the signals. The thermal system within the cabin will allow control of the temperature between 12ºC and 25ºC and the humidity between 45% and 85%, while a large window allows the influence of external heat sources on comfort to be investigated.
Design guides: Reviews of current methods and guidance for the measurement, assessment and evaluation
of the railway environment have been conducted. Four design guides on seating, vibration, noise and motion sickness have been completed which summarize current methods and guidance:
- Seating - The seating design guide provides an aid to the design of passenger seats and driver seats, the improvement of existing seats and the comparison of alternative seats for rail vehicles. Methods of measuring seat dimensions, angles and contouring are defined. Recommendations for the dimensions, angles and contouring of the seat pan, backrest and armrests are based on the principle of matching seat dimensions to the relevant dimensions of the user population. Cushion material, cushion coverings,
the positioning of seat controls and clearances are also considered. Additional considerations for driver seating, including the operation of controls and clearances, are discussed. The seating design guide also contains recommendations for the subjective testing of seat comfort and the dynamic testing of the transmission of vibration through seats.
- Vibration - The vibration design guide outlines current recommendations for predicting the effects of rail vehicle vibration. Various International standards and British standards provide guidance on the measurement, evaluation, and assessment of whole-body vibration with respect to discomfort. The relevant guidance provided in the various standards is summarised. Some specific studies of the effects of vibration on comfort, health and performance are described and the implications of the findings to the assessment of rail vehicle motion are outlined. The vibration causing difficulties in performing such tasks in rail vehicles depend on the spectra of motion and the transmissibility of the human body. The findings of the studies of drinking, writing and reading, all common activities on trains, are summarised.
Oscillation at low frequencies can cause effects that are not caused by higher frequencies of vibration. For example, the effects of low frequency oscillation on postural instability are considered. Methods of predicting the effect of motion on the instability of standing passengers are described.
- Noise - The design guide on the internal noise in passenger trains describes existing guidance and methods relating to the measurement, evaluation, and assessment of noise in rail vehicles. A review of the literature on measurements of noise in trains is included to identify typical noise characteristics.
- Motion sickness - The motion sickness design guide provides guidance and methods relating to the measurement, evaluation and assessment of motion with respect to sickness arising from oscillatory motions in rail vehicles, including the guidance in British and International standards. Research on motion sickness in rail vehicles is also presented.
- Thermal comfort - A design guide on thermal comfort in trains is in preparation.
Thermal comfort research: Research at Loughborough University has been undertaken Mr Paul Underwood and Mr Paddy Stennings, both supervised by Professor Ken Parsons. These two student successfully completed MPhil theses based on the RRUK research. The research was designed to provide
a practical model for the prediction and assessment of thermal comfort in railway carriages. The approach taken was to extend and evaluate an existing thermal comfort model that had been proposed for vehicle environments. The model was based upon the widely used thermal comfort index that is presented in ISO 7730 and modified for the direct effects of solar radiation. This is important for the assessment of thermal comfort in railway carriages as passengers are often exposed to direct solar radiation when sitting next to windows. The research carried out for RRUK involved five laboratory studies in a specially designed solar simulation chamber and a series of practical evaluations in trains.
Paul Underwood conducted three laboratory experiments that built upon previous research. These investigated the effects of: (i) sitting next to a cold window on passenger comfort, (ii) the evaluation of the thermal comfort model for people who are cool at the start of the journey and who would be otherwise cool during the journey if it were not for the sun, and (iii) the effects of colour and fit of clothing on the thermal comfort of people exposed to simulated solar radiation. Human subjects (8 or 16) exposed to simulated solar radiation (or that from a cold window) carried out a standard protocol where skin temperatures were measured as well as subjective thermal comfort and sensation responses over a 30 minute exposure. The results indicated that the thermal comfort model could be used over the range of the thermal comfort scale (i.e. hot to cold conditions); and quantified the effects of sitting next to a cold widow and the effects of clothing. These factors were integrated into an improved thermal
comfort model that was evaluated in a series of trials in railway carriages carried out on journeys between Loughborough and London. The results of the trials in trains indicated that the new thermal comfort model was an improvement on previous models.
Mr Paddy Stennings conducted two laboratory studies that extended the work. The first was to investigate
whether the duration of the train journey is important in terms of thermal comfort in railway carriages. Human subjects were exposed to solar radiation for 60 minutes in the standard protocol and the responses of 16 subjects, after 30 minutes exposure, were compared with those after 60 minutes exposure.
The second was conducted after the subjects had been continuously exposed to the simulated solar radiation for 60 minutes and the thermal comfort responses were recorded when the subject was immediately placed in the shade and the responses when the subject was immediately taken out of the shade. This simulated the sun going behind a cloud or the train, going into a tunnel of changing direction. The results showed no practical difference between responses at 30 minutes and those at 60 minutes exposure. This is as was hypothesized for the conditions which are in the thermal comfort
region. Removing and re-introducing subjects to solar radiation had rapid effects on subjects and implied that although there was inertia in terms of responses, a practical interpretation would be that subjects generally responded to the conditions to which they are exposed at that time. Trials on trains between Loughborough and London to evaluate the thermal comfort model included 8 and 6 subjects in two separate trials. In the second trial, the environments were also assessed by researchers from the University of Southampton who measured the vibration and noise in the railway carriage and also took subjective measures of the absolute and comparative effects of environmental components on thermal comfort. The results of both studies are being integrated into a simple design guide for the prediction and assessment of thermal comfort in railway carriages.
Railway passenger field vibration studies: During the RRUK project, the ISVR researchers have carried
out collaborative work with industry including fundamental research, rail vehicle testing, seat testing and representation in legal cases. Work for one UK-based rail company contributed to the reduction of the vibration exposure of employees to vibration in Multi purpose vehicles. Multi purpose vehicles are used for general track maintenance (weed spraying, fire control, etc.) and rail maintenance (de-icing, leaf cleaning, applying Sandite, etc.).
A total-system approach was adopted to analyse the vibration transmitted from the wheel to the seat. In the field, motions between the vehicle frame and the four corners of the suspended cab and between the cab floor and the surface of the suspended seat were measured and assessed. The effect of altering the vehicle suspension and the set-up of the operator’s seat upon ride comfort within these vehicles was investigated to minimise the vibration exposure of employees. Within the HFRU laboratories, the effects of the suspension seat set-up upon the vibration transmitted to the operator were also assessed using recorded motions reproduced on an electro-hydraulic vibrator. The response of the seat as a function of frequency the suitability of the seat for this particular environment was assessed and recommendations made for an alternative.
Occupational exposures to vibration were assessed for crew on Eurostar 373 class trains between London and Paris, and London and Brussels in accord with the European Union Physical Agents (Vibration)Directive (2002/44/EC) and International Standard 2631 (1997). Exposures were evaluated for occupants of the driving cab, catering staff, and the train managers. From measurements of acceleration on the floor and the seat surfaces it was determined how the magnitude of the vibration and the frequency composition of the vibration depended on the measurement direction and the location of an operator within the train and the ability of the seats to isolate the body from vibration.
In similar measurements for another UK rail company, occupational vibration exposure was assessed on a Matisa P95UK track renewals train in accord with Railway Group Standard GM/RT2160 (Issue 2). Expert witness was provided to North West Trains in a legal case brought by an employee claiming damages as a result of injury allegedly caused by driving trains. In-vehicle measurements were made to assess daily and lifetime exposure of the employee in the context of standards available at the time and the applicable state of knowledge.
A field study was conducted to compare the application of procedures described in the alternative standards for predicting vibration discomfort in rail vehicles. Vibration was measured during a scheduled rail service and was evaluated and assessed according to the guidance in each standard. The effects of differences between the standardised procedures on the assessment of vibration with respect to rail passenger discomfort were investigated. The results demonstrated that the evaluation methods described in the diff erent standards can lead to diff erent conclusions with regard to the predicted vibration discomfort of a rail journey.
A field study was conducted to investigate the combined effects of vibration, noise and thermal environment on passenger discomfort. Vibration, noise and thermal measurements and passenger assessments of vibration, noise and thermal comfort were obtained during a scheduled rail service. The results will be employed together with results from future laboratory studies to determine methods of evaluating rail passenger comfort with respect to the combined effects of vibration, noise and thermal
environment.
Research - Postural stability: Oscillatory motions can cause injury in trains when standing passengers or crew lose balance and fall. To predict the loss of balance of standing people, a model is required of the relationship between the input motion and the stability of the human body. An experimental study, partly funded from RRUK and partly from the EU, was conducted by Dr Naser Nawayseh to investigate the effect of frequency, magnitude, and direction of oscillation on the postural stability of standing subjects and whether response to rotational oscillation can be predicted from knowledge of response to translational oscillation.
Twelve male subjects stood on a floor that oscillated in either horizontal (fore-and-aft or lateral) or rotational (pitch or roll) directions. The oscillations were one-third octave bands of random motion centred on five preferred octave centre frequencies (0.125, 0.25, 0.5, 1.0, and 2.0 Hz). The horizontal motions were presented at each of four velocities (0.04, 0.062, 0.099, 0.16 ms-1 r.m.s.) and the rotational motions were presented at each of four rotational angles (0.73, 1.46, 2.92 and 5.85° r.m.s.) corresponding to four accelerations (0.125, 0.25, 0.5, and 1.0 ms-2 r.m.s.), where the acceleration is that caused by rotation through the gravitational vector. Postural stability was determined by subjective methods and by measuring the displacement of the centre of pressure at the feet during horizontal oscillation.
During horizontal oscillation, increases in motion magnitude increased instability and, with the same velocity at all frequencies from 0.125 to 2.0 Hz, most instability occurred in the region of 0.5 Hz. Fore-and-aft oscillation produced more instability than lateral oscillation, although displacements of the centre of pressure were similar in both directions. With the same angular displacement at all frequencies from 0.125 to 2.0 Hz, pitch oscillation caused more instability than roll oscillation, but in both directions instability increased with increased frequency of oscillation. Frequency weightings for acceleration in the plane of the floor during translational and rotational excitation show the significance of low frequency translational oscillation and high frequency rotational motion, and show that it is necessary to know whether the measured acceleration is caused by translation or rotation through gravity.
Research - Motion sickness: The Human Factors Research Unit participated in the EU-funded FACT (Fast and Comfortable Trains) project, conducting both laboratory experiments and analysing the results of field trials. Subsequent to the end of the EU funding, further experimental studies were conducted
by Mr Barnaby Donohew and Miss Judith Joseph to extend understanding of factors that cause motion sickness and assist the development of a predictive model for motion sickness in tilting trains. These studies contributed to the PhD thesis of Mr Donohew and the ongoing PhD research of Miss Joseph. The work shows that motion sickness can be increased by the tilting of a train but that the effect
is dependent on a complex combination of the lateral acceleration and the tilt, so that tilt can both reduce or increase sickness with an optimum tilt less than that required to fully compensate for lateral acceleration. It is hoped to continue these studies to evolve a more complete mathematical model of the causation of sickness in tilting trains.
OUTPUTS
Project Reports:
Publications:
- Donohew, B.E., Griffin, M.J. (2007). Low frequency motions and motion sickness on a tilting train. Proc. IMechE Vol. 221-1 Part F: J. of Rail & Rapid Transit. pp. 125-134.
- Donohew,B.E. (2006). Motion sickness with lateral and roll oscillation. PhD thesis, University of Southampton.
- Joseph, J.A. (2006). Effect of the magnitude of 0.2 Hz roll oscillation on motion sickness. Presented at the 41st United Kingdom Group Meeting on Human Responses to Vibration, held at QinetiQ, Farnborough, Hampshire, England, 20 – 22 September 2006.
- Nawayseh, N., Griffin,M.J. (2006). Effect of frequency, magnitude and direction of translational and rotational oscillation on the postural stability of standing people. Journal of Sound and Vibration 298. pp. 725–754.
- Donohew, B.E., Griffin,M.J. (2004). Motion Sickness: Effect of the frequency of lateral oscillation. Aviation, Space and Environmental Medicine, Vol. 75, No. 8, August 2004.
- Howarth, H.V.C. (2004). A comparison of standardised methods of evaluating rail vehicle vibration with respect to passenger discomfort. Published in: Proceedings of the 39th UK Conference on Human Response to Vibration, held at Ludlow, Shropshire, England, 15 - 17 September 2004.
- Donohew, B.E., Griffin, MJ., Quétin, F., Gautier, P-E., Cléon, L-M. (2003). Predicting motion sickness on tilting-trains - Application to field test results with the experimental tilting TGV. Proceedings from the World Congress on Railway Research, held at Edinburgh International Conference Centre, 28th September- 1st October 2003.
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