Updated

Yeehaw! Texans who brag they do things bigger and better now can go faster too.

State transportation officials on Thursday boosted speed limits on two stretches of rural highway from 75 mph to 80 mph — the United States' highest posted speed limit.

More speed signs will be changed in the next few days in 10 mostly rural counties in West Texas: a 432-mile stretch of Interstate 10 between El Paso and Kerrville, and 89 miles of Interstate 20 between Monahans and the I-10 interchange at the cusp of the Jeff Davis Mountains.

Congress set a national 55 mph speed limit in the 1970s but it was abolished in 1995. Twelve states besides Texas have speed limits of 75 mph on some roads.

While drivers on I-10 can blow by the sleepy town of Sonora, highway safety advocates warn the higher speeds will cause more fatal crashes.

"This will result in more deaths. The research is pretty clear about that," said Russ Rader, spokesman for the Insurance Institute for Highway Safety. "You get someplace faster but at what cost?"

The Legislature first approved raising the speed limit from 70 mph to 75 mph in 1999, then approved the bump to 80 by a unanimous vote last year.

"You can repeal the speed limit law, but you can't repeal the law of physics. People don't survive crashes at these excessive speeds," said Tom "Smitty" Smith, Texas director of the consumer advocacy group Public Citizen.

State officials say the roads can accommodate the higher speeds.

"We studied it," said Transportation Commission Chairman Ric Williamson. "These are parts of the state where higher speeds is a safe decision."

Mike Behrens, executive director of the state transportation agency, said the new speed limit will affect only a fraction of the state's 70,000 highway miles.

The affected roads are mostly straight shots through the West Texas flatlands that get relatively little traffic.

Agency studies found 85 percent of drivers on those highways are already cruising between 76 mph and 79 mph, said Carol Ranson, deputy director for traffic operations.

"We feel the speeds are safe for the driving public," Ranson said.

But Rader said many drivers push beyond the speed limit if they can do it without getting a ticket. Drivers cruising at 80-85 mph now are likely to push to 90 mph if they can, he said.

As for those high gasoline costs, the Department of Energy says that gas mileage decreases rapidly after 60 mph. The government estimates that every 5 mph over 60 is like paying an extra 20 cents per gallon for gas.

Williamson said the state isn't responsible for drivers "who choose to consume their wealth."