CAPÍTULO V: METODOLOGÍA ESTUDIO SOBRE LAS TIC Y
6. Credibilidad del estudio
Driving simulation continues to be a popular focus for applied driving research, especially in training and assessment. A wide range of simulators have been developed specifically for driver evaluation and these have become increasingly sophisticated, paralleling advances in modern technology (Aaronson, 1 994 ). Many of the earlier models are now virtually obsolete.
I n a comprehensive review, Forbes ( 1 982) identified five approaches or modes of simulation, for all of which visual input is the predominant concern. First, there are static models which rely on a slide projector or a television camera as a fixed-base stimulus set. This type of model is limited by discrete measurement settings, and i s intended for planning more than the measurement o f dynamic interaction o r simulation of specific tasks. Second, there are moving-base stimulus sets, characterised by a conveyer belt-type roadway which creates the illusion of forward movement within the system. Like the static model , these simulations are suitable for i nvestigating a restricted range of driver abilities in a context where a v i sually i mpoverished environment is of little importance. More complex hybrid systems, combini ng the above models, are a third type of simulation, which involves a recorded image projected onto a static background (Biaauw, 1 982). An important advance in this area
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was a model road system on a turntable base, which projected moving scenes across t he driver's wi ndscreen view ( Professor G. Shouksmith, personal communication, 30 September. 1 996 ) . However, before the full potential could be realised, such methods have been overtaken by other types of computerised simulation.
The fourth type of approach is the pre-recorded visual display encompassing a scale mode l or actual road scene on film, videotape or videodisc, which depicts a non repetitive simulated trip and roadscape. This type of simulation is more realistic than static and moving base models, as it allows interaction between the subject operator, vehicle and environment. Current versions are usually interfaced with a computer to record subject responses (Schiff, Arnone & Cross, 1 994). Predetermined time and spat i a l constraints are the main limitations on this type of simulation. A fifth model comprises computer-generated visual stimul us-sets which responds to numerous aspects of driver-related skill (Gianutsos, Campbell & Mandriota, 1 992; Gianutsos, 1 994: Me Knight & McKnight, 1 994 ). More specific subject interaction is possible w i t h both of these latter types of simulation, yet there are limitations in the responses recognised and processed by the simulator, and on the available size of the visual image and graphics.
W h i le di fferent simulations have their own features, there tends to be some common
g ro u n d i n the major advantages and disadvantages u nderlying all simulation met hodology to date. Most models operate under the assumption that psychophysical changes brought about by certain loads, or situations created, correlate with changes in driver performance. However, as Forbes ( 1 982) points out, 'whole-task simulation' is
a fal lacy as it has thus far been impossible to reproduce the living environment which drivers have to negotiate. It is difficult, therefore, to assess the ecological validity of t hese art i ficial settings. A more objective analysis might question how much realism is
appropriate for the targeted goals of a specific simulator system (Aaronson, 1 994 ). Cost and participant discomfort are also constraints on more complete or realistic
s i mu l ation ( Aaronson, 1 994).
The value of any simulator must be dependent on its ability to elicit the same sort of behavioural response from the operator that would be made in a real situation. Many studies fall short of employing techniques for determining whether such a behavioural correspondence exists (van Zomeren et al. , 1 987). Furthermore, simulated systems contain deficiencies in information and are restricted by the fact that they are data driven. Nevertheless, when used in conjunction with practical driving assessment,
DRIVING MEASUREMENT
there are advantages in isolating specific tasks and scenarios for analysis. Notably, simulation can imitate a dynamic parameter, such as hazard identification, in a way that it can be more readily and consistently measured. A situation is created in which the researcher is able to control extraneous variables or to separate factors that are confounded in nature ( Aaronson, 1 994 ). This establishes reproducibility and provides a basis for comparative studies.
Nevertheless, one area of concern is the physical correspondence between simulated and real situations. For a number of reasons, an individual may negotiate and perform quite differently in front of a simulator as he or she would perform in a moving vehicle. For example, absence of kinesthetic feedback is a very relevant factor, although some of the more sophisticated systems have the scope to develop these types of parameters ( Blaauw, 1 982). Obviously, a match of both behavioural and physical components of a simulation with the actual driving task is important. In addition, the artificiality of a driving simulation may evoke different demands on a task so that it is not representative of actual driving. For example, there is debate concerning the amount of positive transfer between aspects of actual driving and simulation of a task or skill factor. Conflicting evidence for age-related effects on adaptability to driving simulators provides a good example of limitations within an assessment context (Cimolino & Balkovec, 1 988; McKnight & McKnight, 1 994; Schiff et al. , 1994 ).
A positive feature of driving simulators is the reduction of risk associated with on-road driver testing. Ethical concerns relating to the safety of subjects and other road users during the assessment process tend to be alleviated when the task is simulated. This can be particularly important where there is the question of a subject's fitness to drive ( Katz et al ., 1 990). Gianutsos ( 1 994) also notes that simulation can inspire confidence and insight as well as objective feedback of results which subjects can relate to as a phase of driving assessment. There is no doubt that today's simulation technology is a much more realistic and exciting prospect for evaluation of the driver. However, high costs involved, particularly with high fidelity simulation, remains a severely limiting factor for use in research and small scale assessment programmes ( A aronson & Eberhard, 1 994 ).
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