13: Distraction and Inattention

As the traffic demands fluctuate over time, so does the amount of resources that are necessary for safe driving. Blumenthal’s model (Chapter 3) provides an intuitively appealing and simple function that links the driving demands with the attention allocated to them. If we allocated all of our attentional capacities to the driving and adjusted our speed and exposure to various driving situations in such a way that the demands never exceed our maximum available resources for processing the traffic and roadway information, then we could eliminate all the accidents that are due to inattention and “delayed recognition.” Unfortunately, this patently simple suggestion is not as easy to apply as it sounds. When the driving demands are low, when the roadway is monotonous, and when we are fatigued, it is actually very difficult to devote all of our attention to the driving task. We then seek to occupy ourselves with non-driving tasks. This was dramatically illustrated in several studies conducted in the 1970s and 1980s that revealed that drivers’ abilities to recall road signs they had just passed was unexpectedly low: from under 50 percent to as low as 5 percent, depending on the “relevance” of the sign and the study methodology (see Chapter 5, and Martens, 2000). To gain some insight into the process, Summala and Näätänen (1974) had drivers drive in naturalistic traffic conditions and report all signs as they encountered them. With this specific instruction, cueing the drivers in advance to attend to and report the signs, the drivers were able to correctly report over 98 percent of the signs they encountered. However, the researchers noted that the drivers invariably commented that driving while attending to all signs was “extremely fatiguing” (or “difficult,” using Fuller’s 2002 term). We can empathize with this fatiguing effect if we compare how tired we feel at the end of a long drive in congested stop-and-go traffic versus a drive lasting just as long on a divided highway in fair weather with little traffic. In the former case, we must allocate nearly all of our attention to changing traffic signals, weaving drivers, and stop-and-go traffic, whereas in the latter case we can relax and allocate much of our attention to non-driving tasks such as listening to music.