New crash tests of full-size pickup trucks are raising troubling questions about the safety of the popular Ram 1500.
The Insurance Institute for Highway Safety, which released its latest round of test results on Tuesday, assigned the Ram 1500 an overall rating of "marginal" — its second-worst of four designations.
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What's more, the pickup's structure earned the worst-possible "poor" rating, following its performance in tests that replicate small overlap front crashes. In those tests, the front corner of a vehicle hits another vehicle or pole. It is one of the most common and deadly accidents.
"In this crash mode we want to maintain the structural integrity of the occupant cabin," said Raul Arbelaez, vice president of the Institute's Vehicle Research Center. "We had [with Ram] more intrusion than we'd like to see, and that led to elevated injury measures on the dummy's lower extremities."
In response to the findings, Ram's parent company Fiat Chrysler said its vehicles meet or exceed all applicable motor-vehicle safety standards.
"Our vehicles are designed for real-world performance and no single test determines overall, real-world vehicle safety," spokesman Eric Mayne said.
The results come as Ram is riding a wave of greater demand for pickups and lower fuel prices, which have helped boost its sales. Last year, Fiat Chrysler sold 451,000 Ram pickups, compared with just 177,000 in 2009.
IIHS crash test ratings are closely watched within the auto industry, and are often used by automakers as a measure of how safe their vehicles would be if they were involved in a crash.
's F-Series was the only model tested that earned the highest overall rating, "good," and was deemed an IIHS Top Safety Pick.
The F-Series, which has panels made of high-strength aluminum that are lighter than the steel used on other pickups, has been the target of ad campaigns run by competitors, which suggest the aluminum body is not as strong as steel — and therefore not as safe.
Arbelaez dismissed that suggestion in an interview with CNBC.
"What I would tell any consumer going out there looking for a new pickup truck is I would clearly go out and look at the Ford F-150," he said.
Ford called the crash tests further proof its new F-Series pickup is not only lighter and more fuel efficient, but also safe.
"We spent thousands of hours engineering, designing and developing multiple safety features that work together in the event of an accident," said Raj Nair, an executive vice president at Ford.
Questions? Comments? BehindTheWheel@cnbc.com.