SNCF has conducted an important research project on global comfort on board main lines trains, called ACONIT (Approche globale des composantes du CONfort et de leurs Interactions pour les Trains grandes lignes) whose objectives were to study passengers comfort representation and to propose improvements in comfort specifications. Before ACONIT, comfort was defined by SNCF experts. For instance, some experts carried out experiments with robots demonstrating the influence of sensorial aspects (resonance, vibration, vision, etc.) on the perception of comfort.
The overall idea of the ACONIT project consisted in considering the comfort as a judgment based on a set of complex elements by taking into account the travellers’ point of view.
This project aimed at developing and validating tools and methods for evaluating the passengers' comfort on main lines trains (long-distance) and to suggest improvements taking into account users’ expectations. The goal was to relate analytical research on some specific components of comfort with the overall impressions of the users in order to be able to specify the relevant improvements for comfort on trains.
The methodology is based on a multidisciplinary approach combining human disciplines with physical ones together with new methods of sensorial analysis generally adopted for new products design. It is based on a five step method:
- The definition of the framework (including the definition of a pre-established comfort model)
- Macro-investigation on the concept of comfort
- Investigation on comfort components and their interactions
- Defining conditions for performing a simulation of real conditions in order to identify possible improvements
- Defining a methodology for comfort evaluation based on results of the research.
During the first part of ACONIT, different surveys have been carried out with travellers by SNCF experts and a supporting team of psycholinguists in order to catch how travellers perceive and define comfort.
The project allowed defining the relevant comfort components and their interactions from passenger's opinions collected during surveys on board commercial trains: TGV, CORAIL and TEOZ in first and second class. In a second step, the correlation between subjective assessments of some comfort components (dynamic, acoustic, thermal and lighting) and physical measurement of the same components was also carried out.
This work led up to recommendations to improve comfort specifications and identified future research needs in the field.
ACONIT project provided moreover approved methodologies to assess passenger perception and compare subjective and physical measurements:
- A way to measure assessment of comfort by people, based on cognitive linguistics, has been developed and approved in close cooperation with the LCPE laboratory (CNRS and Paris VI University). The method consists in collecting passengers' conversations about their travel and their feeling of comfort with the help of a questionnaire constituted of open questions and filled during a commercial journey. This enquiry enables to collect linguistic cues which are analysed for the identification of the global organization of semantic representations. Some specific devices of passengers’ conversations inform furthermore about their sensorial perceptions during their travels. The formulation of questions as well as the order of questions have been cautiously studied to avoid the collection of conventional conversations and catch comfort parameters relevant to passengers' perception.
- The identification of comfort components from passengers' conversations allowed to build a questionnaire constituted of closed questions to assess passengers' judgments on these components. The formulation of closed questions is a result of the categories quoted by passengers in the first step combined with the objective of comparing subjective measurements with physical measurements carried out in the same time during the same travel. Physical components (acoustics, dynamics, thermal and illuminance on table) have been measured with a device called OCTAVE (Outil de mesure du Confort Thermique, Acoustique Vibratoire et d’Eclairage). The work carried out to correlate subjective and physical measurements led up to recommendations to improve comfort specifications on acoustics, dynamics and thermal aspects whereas lighting aspects still need to be investigated to define the adapted physical variable.