Thread by @jamesdouma

@1LoafOfMeat Graph is their public data with averaging applied. I can't rule out them lying. I have put significant effort into trying to find a better way that they could release the data to inform users without making the confusion worse - and I couldn't come up with one. /1

@1LoafOfMeat After pulling the NHTSA crash database and breaking it down many different ways I was unable to find a simple, clear, and accurate way to convey crash statistics. Every approach I came up with had the potential to be gamed by cherry picking thresholds and definitions. /2

@1LoafOfMeat There are dozes of road types and many categories of accidents with a panoply of causes and confounding factors. And there aren't all that many accidents so you can't get statistically significant for any narrow category. /3

@1LoafOfMeat On top of this (for NHTSA data) reporting is done locally and varies by jurisdiction - and quality can be poor so there's subjectivity in deciding what to throw out. A lot of it is clearly erroneous. The NHTSA's own summaries are quite nonspecific for this reason. /4

@1LoafOfMeat Just trying to find incident rates for highway versus city driving is maddeningly and depends on subjective decisions. Any number you present can validly be argued away. The only simple and true statements are about broad categories with tight definitions. /5

@1LoafOfMeat Which is one reason fatalities feature so prominently in statistics. Death is well defined but injuries less so, accident even less so. Incident, crash, damage - all have subjective thresholds of many types. /6

@1LoafOfMeat And definitions are critical because adding or removing just a few 'incidents' to the list can change the 'statistics' a lot. NHTSA has hundreds of pages of categorization rules and they still aren't enough. /7

@1LoafOfMeat In the end broad and simple, if perhaps vague, is probably the best we can do for public facing information. Why trust it? Well for one thing NHTSA gets access to the raw data so lying in a big way would be 1) hard to get away with and 2) extremely damaging when found out. /end