Four of eight new midsize sport utility vehicles scored "good" ratings in crash tests, and none of the SUVs recorded a "poor" rating, an encouraging sign according to the insurance group which conducted the study. General Motors Corp., however, posted mixed results. Its new midsize SUV, the Chevrolet TrailBlazer, and the Pontiac Aztek both scored "marginal" results in the crash tests, conducted by the Insurance Institute for Highway Safety (IIHS). GM's Buick Rendezvous and Isuzu Motors Ltd.'s Axiom both scored an "acceptable" rating in the crash tests done by the insurance industry group, which lobbies the auto industry to improve the crashworthiness and safety of vehicles. The IIHS's offset crash test seeks to determine how well occupants would survive in a vehicle if the driver's side of the front end slammed into a barrier at 40 miles per hour. GM, questioning the IIHS' results, said in a statement that it puts its vehicles through dozens of crash tests and computer simulations, beyond the single test conducted by the insurance group. "This test does not reflect the wide variety of crash modes that GM considers in the design, engineering and testing of our vehicles, nor can it account for all of a vehicle's crash avoidance capabilities," GM said in a statement. The test on the Chevrolet TrailBlazer, which is structurally similar to the GMC Envoy and Oldsmobile Bravada, showed a risk of head injury after the head of the crash dummy struck the pillar between the front and rear doors. Nevertheless, the IIHS noted that the new TrailBlazer, a key vehicle in GM's product lineup, showed an improvement over the Chevrolet Blazer, which scored a "poor" rating. The TrailBlazer replaces the four-door Blazer, but GM still produces the two-door Blazer. Ford Motor Co. asked the insurance group to delay testing its new 2002 Ford Explorer until it makes additional structural adjustments to beef up the SUV. Two Ford trucks, the F-150 pickup truck and the Escape small SUV, scored disappointing results in the insurance group's crash test this year. Ford's safety record has been closely watched since last year's recall of 6.5 million Firestone tires, most fitted on Ford vehicles. Nashville-based Firestone, a unit of Japan's Bridgestone Corp. , attacked the safety of the Ford Explorer after Ford Motor Co. recalled another 13 million Firestone tires this spring. Scoring a good rating in the crash tests were Honda Motor Co. Ltd.'s Acura MDX, Toyota Motor Corp.'s Highlander, Suzuki Motor Corp.'s Grand Vitara XL-7 and Mitsubishi Motors Corp.'s Montero Sport SUVs. "This is encouraging," IIHS President Brian O'Neill said. "In the past when we've tested a group of vehicles, we usually haven't gotten so many good performers, and we usually get at least one poor performer. But offset crash test performances have been getting better, as this group of vehicles demonstrates."