How we count
Exactly how complaints per year on the road, the complaint index, the early-life trend, recent activity, vehicle age at incident and the excerpt selection are computed.
Where the data comes from
Complaints and recalls are fetched from NHTSA's public API for each tracked make, model and model year. Defect investigations come from NHTSA's investigation flat file. A complaint is a report filed by a vehicle owner; it is not verified by NHTSA and does not prove a defect. Recalls are formal safety campaigns reported by manufacturers. Investigations are NHTSA's own inquiries (preliminary evaluations, engineering analyses, recall queries and audit queries) and its reviews of defect petitions filed by the public; every entry on this site is labelled with its type.
Nameplate variants
NHTSA files the same vehicle under several names: body styles, cab configurations, hybrid and plug-in versions. We resolve every variant of a nameplate for each model year and combine them into one page. Distinct models that share a word — Corolla Cross, Bronco Sport, Mustang Mach-E — are tracked separately, not merged.
Complaints per year on the road
Older model years accumulate more complaints simply because they have existed longer. We divide the complaint count by the years elapsed since January 1 of the model year, with a minimum of one year. This is the primary figure used for comparisons and rankings.
Complaint index
The index divides a vehicle's complaints per year by the average of a comparison group: all tracked vehicles, the same brand, the same model year, or the same segment. 1.00 equals the group average; 2.00 means twice the group's rate. The bands used in text are: far fewer (below 0.50), fewer (0.50–0.79), typical (0.80–1.24), more (1.25–1.99) and far more (2.00 and above).
Early-life trend
Complaint filing has increased in general over recent years, so comparing raw counts across model years would make every model look worse over time. To measure whether a model is improving, we count only complaints filed within the first 24 months after January 1 of each model year, divide by the average early-life count of all tracked vehicles of that same model year, and compare the newest two closed model years with the oldest two. A change of 25% or more in either direction is labelled improving or worsening; anything smaller is stable. Model years whose 24-month window has not closed are excluded.
Recent activity
We compare complaints filed in the last 12 months with the 12 months before. A change of 30% or more is labelled rising or falling; with fewer than 20 complaints across both windows no label is given.
Vehicle age at incident
Each complaint carries the date of the incident. We measure months between January 1 of the model year and that date and report the distribution in five bands and the median. Because vehicles are sold before their model year begins, some incidents fall at month zero.
Component groups
NHTSA tags each complaint with one or more component names. We map those names to twelve plain-language groups (engine, transmission, electrical, brakes and so on). A complaint that mentions several components is counted once, under the first group that matches in a fixed order that starts with engine, transmission and electrical; this is not necessarily the component the owner listed first. The group labelled “Unspecified or other” consists mostly of complaints that NHTSA tags only as “unknown or other”, plus a small number tagged as equipment, interior or air conditioning. Recalls are matched to groups the same way, which decides which recalls a problem page lists as related.
Excerpts
Excerpts are the opening sentences of real complaints, shortened for length; we prefer recent reports and include at most two reports that describe a crash, fire or injury.
Limitations
Sales volumes are not part of this data, so a best-selling model will naturally have more complaints than a rare one; the per-year figure adjusts for age, not popularity. Complaint rates also reflect how likely owners are to file reports, which varies by brand, region and vehicle price. NHTSA data covers vehicles sold in the United States; the same nameplate sold elsewhere may differ in equipment and suppliers. Treat these numbers as one input among many.
Update cadence
The whole site is rebuilt once a month from fresh downloads. The date of the newest complaint in the data appears in the footer of every page.