Methodology
Where the data comes from
Every figure is derived from the US National Highway Traffic Safety Administration's public APIs at api.nhtsa.gov: the owner complaint database and the recall campaign database. Data is refreshed daily. We store no personal information from complaint records.
The severity index
Raw complaint counts reward popularity, not danger - a best-selling sedan attracts more filings than a rare coupe. The severity index instead measures what kind of complaints a vehicle attracts, per 100 filings:
| Event in a complaint | Weight |
|---|---|
| Crash reported | 4 |
| Fire reported | 6 |
| Injury reported | 8 |
| Fatality reported | 40 |
Score = (4xcrashes + 6xfires + 8xinjuries + 40xdeaths) / complaints x 100. The weights are our editorial judgement, chosen so that a single fatality outweighs a large number of non-injury reports. They are not an NHTSA standard.
Limits you should know about
- Complaints are unverified consumer reports, not confirmed defects.
- Counts are not normalised by units sold or vehicle age.
- Media coverage and class actions measurably increase filing rates.
- A vehicle with few complaints may simply be rare.
We publish these caveats because the numbers are only useful if you know what they cannot tell you.