Responding to car buyers' demands for more seats and better fuel efficiency, automakers are putting third-row seats into increasingly smaller models, according to The Wall Street Journal. Across the industry, 57 models are available with third-row seats or offer them as options, up 21 percent from a year earlier. However, the safety of these back rows is largely untested, prompting consumer groups to worry that passengers could more easily be injured in collisions that cause the rear of the vehicle to crumple, The Wall Street Journal reports. Higher gasoline prices have pushed consumers toward smaller, more fuel-efficient vehicles and carmakers are trying to accommodate those who have large families, participate in car pools or otherwise require space for more than five passengers. Advances in auto design have also allowed more SUVs and car-based crossover utility vehicles like the BMW X5 and Ford Motor Co.'s Volvo XC90 to more easily accommodate rear seats that fold unobtrusively flat into the floor of the cargo bay so they're out of sight until needed. Safety advocates say third-row seats often lack basic safety features, such as built-in anchors for child safety seats, and tend to block rear views and contribute to the rising number of accidents in which adults unwittingly run over children when backing up. Some critics say inconvenience more than safety concerns could limit the success of third-row seats. However, more automakers are designing third- row seats to be more functional and easier to reconfigure inside the cabin.