But Dr. Evans says, “The preponderance of visual information over that from all other senses actually increases even further with increasing driving skill levels.” He says that the skilled driver driving a different vehicle with a different steering system, for example, reacts to visual feedback by making the steering input necessary to achieve the desired visual result while remaining relatively unaware of the important differences in the feel of the vehicle.

 

He compares the importance of visual feedback to the skilled driver to the importance of hearing to a skilled musician playing a 3/4-size violin - less a matter of thinking about adjusting finger placement than about listening and responding to the sounds produced.

 

Dr. Evans’ analysis of visual feedback quickly moves further away from the obvious beginnings. In examining the relationship between what the driver sees, and crash risk, he notes that 45 years is both the age at which visual acuity, contrast sensitivity, and the ability to withstand glare have begun to decline and yet is the age at which the crash rate is minimal. He also cites the strange statistic that the loss of one eye has minimal effect on driving safety.

 

Crash risk and visual feedback are closely linked where “the useful field of view” is not accurately or quickly identified. Dr. Evans notes: “From a loosely-structured, but stimuli-rich visual environment the driver must select information that is relevant.” Quickly identifying information crucial to avoiding a hazard, for example, is how visual information processing—pattern recognition— becomes even more “central to the driving task” than just sharp eyes. While good vision is a standard requirement, good decision-making is very much the key to safety.

 

That “effectively processing visual feedback” is a matter of knowing how and where to look is well illustrated in judging speed. Because accurately judging speed is critically important to safe driving, the law requires “metered measurement”, i.e. speedometers. Dr. Evans notes, “Even experienced drivers do not estimate vehicle speed well without instrumentation to assist.”

 

Accurately gauging speed using only visual cues involves using peripheral vision to monitor the changing size and position of peripheral objects, rather than focusing straight ahead on the point from which a straight road appears to emerge. Dr. Evans calls this the “focus of expansion”. Since the focus of expansion changes little when viewed while moving towards it, it provides almost no cues to assist with visually gauging speed.

 

Dr. Evans points out that regardless of driving experience, when it comes to judging speed, there is a phenomenon called “speed adaptation”. Drive at high speed, and then slow down. Seems like the new “slower” speed is OK, but it may still be much too fast when we look at the speedometer. This is a type of optical illusion, which will affect even the most experienced drivers. The lesson is, “check your speedometer frequently”.