General Motors Corp.'s 2002 Chevrolet Blazer sport utility vehicle with two-wheel drive received the U.S. government's worst rollover rating, while Ford Motor Co.'s Thunderbird convertible got the highest mark, according to a Bloomberg News story by Rip Watson. The vehicles were among 26 in the latest ratings by the National Highway Traffic Safety Administration (NHTSA). The ratings use a center-of-gravity equation and aren't based on road tests. Vehicles receive from one star, the worst score, to five stars. Detroit-based General Motors couldn't immediately be reached to comment on the Blazer rating, according to Bloomberg News. The Ford Thunderbird is the seventh vehicle to get the five-star rating, NHTSA spokesman Tim Hurd said. The others are DaimlerChrysler AG's Chrysler Sebring and similar Dodge Stratus cars, Honda Motor Co.'s Accord sedan and three Ford cars -- the Ford Crown Victoria, Mercury Grand Marquis and Lincoln LS. In the latest round, the agency gave two-star ratings to Ford's 2002 Explorer, for both two-wheel and four-wheel-drive models, the four-wheel-drive Blazer and Mazda Motor Corp.'s B-Series four-wheel-drive pickup truck.