Since the creation of those surveys Deffenbacher and others have found that, like most human behavior, aggressive driving
occurs along a spectrum — from mild to annoying to troubling to homicidal.
(Regarding PR, the fraction of PR from one layer that is absorbed by another depends on their optical properties (as well as the optical properties of other layers in between, and other layers if scattering / reflection were to
occur), including variations over the
spectrum and how the temperature change in the layer emitting the PR is distributed, which,
along with optical properties, affects how much PR goes out of a layer from the top or bottom, and where it is found in the
spectrum.