The GMC Sierra 1500 is the best vehicle for protecting passengers from injuries.

If you drive a GMC, a new study indicates that you might be behind the wheel of one of the safest vehicles on the market. The automaker took four of the five top spots in's list of best and worst vehicles for preventing passenger injuries, and the data shows that bigger vehicles may be the safest choice in a collision.

“The laws of physics are always in play in crashes,” says Russ Rader, spokesperson for the Insurance Institute for Highway Safety. “Weight counts. Smaller, lighter cars are safer than they used to be, but all things being equal, people riding in bigger, heavier vehicles get more protection in crashes.” IIHS tweeted a crash test video Tuesday, which shows that size and weight can play a major role in vehicle safety.

To come up with the list of best and worst vehicles, analyzed insurance rates of 750 vehicles in their annual car insurance comparison study, which calculates average insurance costs across six providers (Allstate, Farmers, GEICO, Nationwide, Progressive and State Farm). Cars with the highest costs for Personal Injury Protection (PIP) and Medical Payments (MedPay) coverage were deemed least safe, while vehicles with the lowest costs are regarded as providing better protection.

The GMC Sierra 1500 (SLE, SLT and Work Truck trims) took the top stop for protecting passengers from injuries, followed by the Porsche Cayenne, GMC Yukon (Denali and SLT), GMC Sierra 2500 SLE and GMC Terrain SLE1. In contrast, the Fiat 500 and 500C perform worst among new cars, with Lounge, CLounge, Sport, Pop and Cpop trims being called out in particular. The Kia Rio 5 (LX and SX), Toyota Corolla L, Mitsubishi Lancer Ralliart and Mercedes-Benz CL600 follow close behind, as indicates that passengers in these vehicles are more prone to injury.

Small cars like the Fiat 500 offer less protection than bigger vehicles with similar crash test ratings.

Four of the five worst vehicles are affordable small cars that start at less than $17,500. As a result, a few automotive journalists wonder if some cars have higher insurance costs because they are marketed toward younger drivers. Amy Danise, editorial director at tells that "Driver profile can definitely affect insurance rates, but I think what we're also seeing here is size and weight [of the car] playing a huge part."

Shopping for a GMC Sierra 1500 or another full size truck? Check out the U.S. News rankings of this year's best cars. Then, look for a great deal on a new car by checking out this month’s best car deals. Also, be sure to follow us on Twitter and Facebook.