title: The frequency--severity indeterminacy.
abstract: Nothing is known about unreported crashes; the information we have is of reported crashes only. Whether a crash gets reported depends on its severity. It follows by logic that, using only data about reported crashes, it is impossible to say whether a change or difference in crash counts reflects a change or difference in crash frequency or in crash severity. This indeterminacy has practical implications. Examples discussed are of the misattribution of over-representation in reported crashes of older drivers and of trucks to causal factors related to the frequency of crash involvement, and of misinterpretation by researchers of findings about the rollover propensity of SUVs.
authors.affiliation: Ezra.Hauer@utoronto.ca
authors.forename: Ezra
authors.initials: E
authors.lastname: Hauer
mesh_terms: D000056:Accident Prevention / Q000706:statistics & numerical data*; D000063:Accidents, Traffic / Q000145:classification* / Q000517:prevention & control / Q000706:statistics & numerical data; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D003625:Data Collection; D015981:Epidemiologic Factors; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018986:Motor Vehicles / Q000706:statistics & numerical data; D012306:Risk