Subjects reports of own speed a function of various instructions and environmental factors : a pilot study

One crucial aspect of car driving is the drivers' choice of speed in different situations. The speed level chosen will strongly affect the demands on the drivers' level of attention, quality of decision making, ability to react quickly etc. There is a quite extensive knowledge about the effects of some factors on drivers choice of speed. For instance, Armour (1983) showed that sight distance, width and presence of police have an effect on drivers' choice of speed on local streets. Galin (1981) showed that a driver's age, purpose of the trip, and vehicle age have some effect on the speed chosen in rural settings. This is, of course, a promising start, but it seems likely on intuitive grounds that more factors (or cues) exist that are important for a driver's choice of speed- level. Examples of factors the effects of which are not known, are the driver's estimates of risk, and the effect of being in a hurry. These are examples of factors which cannot, in an easy way, be estimated by observations in traffic. Another type of problem which has not been studied so far, is how drivers combine the effects of different factors. It is also, to a large extent, unknown, what relative weights the drivers attach to the different factors. To investigate this, laboratory research has to be carried out. For instance, to study how drivers integrate, or combine, different factors, it °is necessary to vary these factors in a systematic manner. In real traffic situations factors never present themselves systematically. There is, of course, problems with working in the laboratory. Generally speaking, you will always have uncertainties with the validity of your studies. But - in this case there does not seem to be any option. The only way to investigate these things systematically is in the laboratory