The info comes from federal government sources, but this firm assembles it and puts it in an easy to use spreadsheet format. Agencies only keep the data that's relevant to them. It's hard to boil down complex human behavior to a few fields in a traffic accident report. The databases are often good for counting accidents and finding the most dangerous intersections, but to find out the details of any particular accident, we had to pull the paper reports. It's not easy to determine the severity of an accident.
Police reports on injuries and damage are often way off the mark.
If somebody complains about a minor backache, the police still log it as an injury accident. Likewise, the estimates on the amount of damage to a car can be thousands of dollars off. Still, these are probably the best measurements you have if you're trying to sift out the fender-benders.