Driver Expectancy and Positive Guidance

What expectancy and positive guidance mean

Expectancy is a driver's readiness to respond to situations, events and information in predictable ways. It is built from experience with roads in general and with the particular road being driven. Drivers tend to respond more quickly and more accurately when the road matches what they expect, and more slowly, or incorrectly, when it does not.

Positive guidance is the related principle that a road should give drivers the information they need, where they need it and in a form they can use, particularly ahead of locations that depart from expectation. It is among the human factors concepts used in the design of roadways and traffic control devices in the United States.

How it bears on driving

Expectancy questions arise where the road changes in a way a driver might not anticipate: a lane that ends, an unusual intersection or interchange layout, a curve sharper than those before it, a temporary work zone pattern, or traffic stopped where it normally flows. Whether the available signs, markings and sight lines conveyed the change, and conveyed it early enough, bears on how long a driver needed to respond.

Expectation also shapes what drivers notice. A driver with no reason to expect a hazard at a location may be slower to detect it, even when it is in view. Equally, the analysis may show that the road communicated clearly and that a driver had the information needed. The questions are the same either way.

Questions a driver expectancy expert witness can address

• Did the road, or conditions on it, differ from what a driver would reasonably expect at that location?
• Was the information a driver needed available, and available early enough to act on?
• How did the driver's familiarity with the road bear on what the driver expected and noticed?

This article is general information, not legal advice or an expert opinion on any matter. See the disclaimer.