The 2026 Cadillac CT5 earned a rare “Poor” rating in the Insurance Institute for Highway Safety’s updated side-impact crash test, after instruments recorded a 161-g peak force to the driver dummy’s head — among the more severe head-impact readings IIHS has logged under its tougher new protocol.

According to IIHS’s own published results for the CT5 Premium Luxury sedan, the driver-side test recorded a Head Injury Criterion (HIC-15) score of 1,282, 46mm of torso deflection, and 5.1 kN of combined pelvis force. IIHS rated the CT5’s overall structure “Marginal,” driver head and neck protection “Poor,” and driver torso and pelvis protection “Marginal.” Rear-passenger protection, by contrast, scored “Good” across every measured category.

Why the test suddenly got harder

The CT5’s result reflects a genuinely tougher exam, not simply a weaker car by old standards. IIHS redesigned its side-impact test after research showed real-world side crashes are more violent than the original evaluation simulated. The moving barrier used to strike test vehicles now weighs 4,200 pounds, up from 3,300 pounds, and hits at 37 mph instead of 31 mph — a combination meant to mimic being T-boned by a modern midsize SUV rather than a generic sedan. IIHS says side impacts still account for nearly a quarter of all passenger-vehicle occupant fatalities, which is the reasoning behind raising the bar.

The CT5 isn’t alone in struggling with the new protocol — IIHS has flagged several small and midsize cars that passed the old side test comfortably but scored Poor or Marginal under the new one. But the CT5’s result stood out for the severity of its head-impact reading, and it wasn’t the sedan’s only weak score: IIHS also rated the CT5 “Poor” for rear-passenger protection in its moderate overlap front test, “Poor” for front crash prevention in vehicle-to-vehicle scenarios, and “Marginal” to “Poor” on headlight performance depending on trim and package.

What it means for buyers

A “Poor” side-impact rating doesn’t mean the CT5 is unsafe to drive — every new car sold in the U.S. still has to clear separate federal crash standards regardless of how it scores on IIHS’s voluntary tests. But it does mean shoppers cross-shopping the CT5 against rivals with stronger scores under IIHS’s new protocol should weigh that gap seriously, particularly anyone who regularly carries rear passengers or shares the road with the larger SUVs and trucks the new barrier is designed to simulate. Cadillac has not publicly said whether structural changes are planned for a future model year in response to the result.