The KABCO scale is the nationally recognized crash severity model developed by the U.S. Department of Transportation Federal Highway Administration (FHWA). The KABCO definitions are as follows:
(K) - Fatal Injury
(A) - Suspected Serious Injury
(B) - Suspected Minor Injury
(C) - Possible Injury
(O) - No Apparent Injury
To determine the economic benefits of safety treatments, safety analysts use crash costs to quantify the impacts of crashes reduced by the safety improvement project, according to the FHWA.
Additional information on crash costs can be found in the following excerpt from the FHWA document “Crash Costs for Highway Safety Analysis.”
Highway safety benefit-cost analysis is a critical component of improving safety on our roadways. Highway safety improvement projects—including those implemented through the Highway Safety Improvement Program (HSIP)—must be economically justified such that their expected benefits exceed the costs. To determine the economic benefits of safety treatments, analysts use crash costs to quantify the impacts of crashes reduced by the safety improvement project.
Additionally, crash costs are often used as part of network screening to identify the roadway locations with the highest potential for safety improvement by quantifying the potential reductions in crash costs to roadway users. This guide documents a literature review and the results of a questionnaire sent to all FHWA Division Offices regarding crash unit costs and their application.
Currently, there is no nationally recommended set of crash unit costs for use in highway safety benefit-cost analysis. States independently select, modify, and update crash unit costs from one or more sources for their highway safety analyses.
The Crash Costs for Highway Safety Analysis guide describes the various sources of crash costs, current practices and crash costs used by States, critical considerations when modifying and applying crash unit costs, and an exploration of the feasibility of establishing national crash unit cost values. This guide proposes a new set of national crash unit costs for the FHWA Highway Safety Benefit-Cost Analysis Guide and Tool as well as procedures to (1) update the crash unit costs over time, and (2) adjust the crash unit costs to States based on State-specific cost of living, injury-to-crash ratios, and vehicle-to-crash ratio.
More resources on this topic can be found here: