Everything's bigger in Texas including the speed limit.

A new 41-mile (65-kilometer) stretch of toll road between San Antonio and Austin is now open with an 85-mph (137-kph) speed limit, the highest posted speed limit in the United States.

State transportation officials hope that the speed limit will be an incentive for motorists to pay the roughly $12 toll to drive on the 90-mile (145-km) road.

Joe Krier, who is on the board of the private company that built the new road, said there is no reason why motorists should not drive that fast. "This project was designed to support it, and the engineers are confident with it," he said.

Still, the higher speed has some safety advocates concerned.

"We all worry about safety. Such high speeds lead to worse accidents and a greater loss of life," said Sandrea Helin, president of the Southwest Insurance Information Service.

But some 18-wheel trucks, many of which are hauling items manufactured in Mexico to plants in the United States, may not be keen to take to the new road, according to Darrin Roth of the American Trucking Association. Many trucking companies prevent their vehicles from going faster than 70 mph or 75 mph, he said, and fuel consumption goes up exponentially as speeds increase - potentially cutting into company profits.

"For truck drivers to be on a road where other motorists are going 85 or even more, they just don't feel safe," Roth said.

Texas for 17 years has had a posted speed limit of 80 mph along two interstate highways in the remote western part of the state. The 85 mph limit is the result of a 2011 state law that allows that speed on new highways that meeting stringent safety tests. (Reuters)