According to the Insurance Institute For Highway Safety (IIHS), 2012 Fiat 500 models built after July of 2011 earn a “Top Safety Pick” designation, indicating that they’ve achieved the highest score of “Good” in frontal offset, side impact and roof strength testing.

Even models built before August of 2011 score “Good” in all IIHS tests except frontal offset crash testing, where the diminutive city car managed a rating of “Marginal,” which is the rating above “Poor.” Stick to a Fiat 500 built after July of 2011, however, and the IIHS insists that you’re buying a safer car.

The National Highway Traffic Safety Administration (NHTSA), on the other hand, would beg to differ. In the NHTSA’s latest tests, the Fiat 500 scores an overall rating of three stars (out of five) which isn’t an impressive performance. While the 2012 Fiat 500 scored four stars in frontal barrier crash testing for the (male) driver, the same test yielded a three star rating for a front seat female passenger.

The Fiat 500 did relatively well in rollover testing, producing just a 14.5 percent chance of rollover and earning a four star rating. Side crash testing for the driver produced very good results, too, earning a perfect five star rating.

The problem, according to the NHTSA, is in rear seat passenger crash testing. With a female crash test dummy in the rear passenger seat, the Fiat 500 earned just a two star rating, which dragged the overall rating of the car down.

2012 Fiat 500 Front Impact Test

2012 Fiat 500 Front Impact Test

In the test, a female dummy was positioned behind the male driver dummy for a simulated 38.5 mph simulated intersection crash. The two-star rating resulted from injuries sustained to the passenger dummy’s head and pelvis.

As the NHTSA itself points out, the new crash test standards (revised in 2011) are more stringent than the outgoing standards, so it isn’t possible to compare a previous rating against a new rating. In the agency’s own words, overall vehicle scores should only be compared to other vehicles of similar size and weight.

In other words, it’s only relevant to compare the Fiat 500 against others in the subcompact segment. While no MINI Cooper variants have been tested under the new program, a Ford Fiesta 5 door scored 4 stars overall, but with a “Safety Concern” caveat not reflected in the overall rating.

While today’s smallest cars are much safer than preceding generations, you simply can’t negate the laws of physics. In a crash with a larger vehicle or stationary object, the smallest cars won’t always fare well.