Miscommunications Based on Different Meanings of “Safe” and Their Implications for the Meaning of Safe System

Abstract

AbstractWhile many countries are apparently adopting “Safe System” for road safety, the failure to deliver the vision of zero deaths and serious injuries continues in part due to the lack of a rigorous and agreed definition of “safe” in road safety. Multiple authoritative definitions of the adjective “safe” exist which may be categorized as probabilistic and absolute. While apparently similar, these definitions are in a fundamental sense inconsistent with each other. The probabilistic definition involves degrees of safety, through probabilities that harm is not likely or unlikely, or that there is little risk. The absolute definition presents safety as free from harm or not involving any risk or protected from danger. Road safety is currently communicated as though there is an agreed meaning of safe, but the vital conversation around what is meant by safe is not undertaken because the difference in usage of the term safe is not appreciated. For example, in road design and engineering, road design standards are generally developed to achieve this probabilistic definition of safety and not absolute safety: the road can be described as safe because it by itself (with perfect use) will not cause a crash, even though people still die on it. Based on the absolute definition of safe, such roads are not safe as unambiguously demonstrated by people dying on them. Calls for roads to be made safe employing the absolute definition are often met with the response that they are already safe (in the probabilistic sense), having been built to “accepted” design guidelines. The acceptance of the probabilistic definition of safe for Safe System hinders progress toward its fundamental aims of zero deaths and serious injuries. In order to achieve zero deaths and serious injuries, uniform understanding and acceptance of “safe” adopting the absolute definition is needed.