Safety questions are being raised about small pickup trucks, at a time when sales are up because of their improved gas mileage.

The Insurance Institute for Highway Safety says several small pickups from the 2008 model year offer dismal protection in side crashes. Versions of the Chevrolet Colorado and its twin, the GMC Canyon, not equipped with optional side air bags earn the institute's lowest rating of "poor" in the side test.

Several other pickups were judged "marginal," the second-lowest in the four-scale ratings.

Safety institute president Adrian Lund says people thinking about buying a small pickup, "won't find many that afford state-of-the-art crash protection."

A GM spokeswoman defends the vehicles. She says the institute's test simulates "a very severe crash," and says the Colorado and Canyon have performed well in other tests.