The 1999 Subaru Forester (top) earned high ratings, while the 1998-99 Isuzu Amigo (bottom) earned the lowest ratings in overall performance

ARLINGTON, Virginia (CNN) -- Small sport utility vehicles (SUVs), which didn't do well in low-speed crash tests a few months ago, were equally disappointing in new tests where the crash speed was increased.

The 1999 Subaru Forester was the only small SUV tested in a 40 mph "frontal offset" crash that earned an overall rating of "good" from the Insurance Institute for Highway Safety.

Four vehicles were rated "acceptable": Jeep Wrangler (1997-99 models); Suzuki Grand Vitara (1999); Suzuki Vitara (1999 models); and Chevrolet Tracker (1999 models).

Four vehicles were rated "marginal": Kia Sportage (1998-99 models); Honda CR-V (1997-99 models); Jeep Cherokee (1997-1999 models); and Toyota RAV4 (1996-99 models).

The worst performer was the Isuzu Amigo (1998-99 models). It was the only small SUV tested to receive a "poor" rating in the frontal offset crash test.

The Amigo is built on a truck body while the Forester, which is smaller, is on a car frame.

"As this test series shows, most of these vehicles aren't going to offer the kind of protection they should be offering in the event of a serious frontal crash," said IIHS President Brian O'Neill.

Each vehicle's overall evaluation is based on three aspects of performance:

• How far the front of the vehicle pushes back into the occupant area after impact. "The driver space in the Forester was maintained reasonably well, with limited intrusion, while in the Amigo there was major collapse of the occupant compartment," O'Neill said.

• Injury risk measures from a crash dummy in the driver's seat.

• Analysis of slow-motion film to assess how well seat belts and air bags controlled dummy movement during the crash test.

In July, the institute announced the results of its low-speed crash tests on seven small SUVs, all 1998 models. The Forester required the least expensive repairs ($2,207) while the Sportage required the most expensive repairs ($7,309).

The institute's crash tests did not address the propensity of small utility vehicles to roll over. As a group, they historically have much higher fatal single-vehicle crash rates than other passenger vehicles, the institute said.

Detroit Bureau Chief Ed Garsten contributed to this report.