Top Safety Pick is the IIHS award for vehicles that earn good results across its crash tests and meet its crash-avoidance and headlight criteria — it is a pass/fail badge on top of the individual ratings, not a score.
How a car earns it
The IIHS rates each test Good, Acceptable, Marginal or Poor. To win the award a vehicle has to earn good results in the crashworthiness tests and meet the criteria for headlights and crash prevention. TSP+ is the higher tier, with stricter requirements.
The requirements get harder over time, which is deliberate: the award is meant to push the market, not to describe a fixed standard. That is why the award year matters as much as the award.
How it relates to NHTSA stars
They are two independent US programmes. NHTSA is the government programme and gives stars per crash type; the IIHS is funded by insurers and gives word ratings plus the award. A car can do well in one and less well in the other because they run different tests.
Read both. On MotorHangar each model-year page shows every programme that tested that car, each labelled with where the rating comes from.
